DD140740A5 - PROCESS FOR SLUDGE RINSING - Google Patents

Description

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'A process for sludge under aerobic / anaerobic conditions;. _

Field of application of the invention

The present invention generally relates to a process for warm sludge digestion under aerobic and anaerobic conditions.

• There has been a corresponding increase in problems related to wastewater disposal as industry and the population continue to grow. Although physical, chemical and biological treatment «. Systems have been developed that can effectively treat polluted Y / asaer to reach a wastewater that is suitable _? For release through natural waters, almost all basic wastewater treatment systems currently in use, including clarification, chemical precipitation, biological filtration and activated sludge, convert the water contaminants into a concentrated form containing the sludge forms. Especially in the activated sludge process, which is to be expected to the most common methods of conventionally used wastewater treatment systems »there is usually a significant

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te, absolute net production of volatile suspended Peststoffen (MLVSS) _s d * h _e, the rate of cell synthesis exceeds the rate of cell degradation "Therefore, there is an increase in the sludge and excess activated sludge needs to be discharged from the process continuously or periodically"

Since the total volumes of wastewater requiring treatment increase, especially under conditions of strict increasingly legislation to control pollution, the amount increases to waste sludge according to the above-mentioned wastewater treatment process in an appropriate manner _e Polglich is highly the desire to use this waste sludge in such a way that it can be readily and economically exploited

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Paths can be eliminated without contributing to further pollution of the ecosphere · While great efforts have been made to develop improvement both in ^J of sludge treatment technology and in terms of refining the existing sludge treatment process, there is still a great need for BES \ serums and more effective sludge treatment systems ·

The basic objective of all sludge treatment processes is to economically and effectively reduce and stabilize the sludge solids. In addition, the sludge treatment system also desirably must provide a final product which is fully suitable.

.J). Without further physical or chemical treatment, it will be definitively eliminated. "In conventional practice, sludge removal is generally carried out by either dumping the sludge into the sea, incinerating, dumping or distributing the soil © In many cases soil remediation is used and this is particularly attractive due to the minimal long-term environmental effects · In fact, the soil distribution of the sludge can be considered highly beneficial to aid the regeneration of the soil * The use of soil distribution in terms of a final sludge disposal process requires

_x but a well-pasteurized final product, so that the concentration. tion of pathogenic organisms in which sludge is sufficiently low to avoid any potential health hazard in the distribution of the sludge »

Traditionally, three different methods of treating sludge have been extensively utilized: oxidation basins, anaerobic digestion and aerobic digestion.

Oxidation basins are generally used in the form of comparatively shallow excavated basins in the soil,

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· These basins offer the possibility of biological oxidation of the organic material by the natural or artificially accelerated transfer of oxygen from the ambient air to the water · During the process of bio-oxidation become the pesticides Biodegraded to a certain extent in the effluent and eventually settling at the bottom of the basin, where they can become anaerobic and continue to be stabilized. "Periodically, the basin may be emptied and the settled sludge may be dredged to increase its absorption capacity Renewing the basin for further wastewater treatment * The extracted sludge is used, for example, for soil disposal «Oxydation basins thus represent a functionally simple system for the treatment of sewage and sludge« The use of oxy However, it is of limited use because the maintenance of such basins requires rather large floor areas. Moreover, this treatment and disposal method does not significantly reduce the concentration of pathogenic organisms in the sludge.

Anaerobic digestion has generally been the most extensively used potting method for stabilizing concentrated organic pesticides as they are removed from settling tanks, biological filters and activated sludge plants. In general practice, the excess sludge is collected in large, curved sludge digestion tanks where The main reasons for the commercial takeover of anaerobic sludge digestion are that this process is able to stabilize large volumes of dilute organic insemination that it contains too small amounts of biological sludge Pesticides (biomass) contributes to a relatively easy-to-drainage sludge.

In addition, it has been alleged on several occasions that anaerobic pelleting produces a pasteurized sludge. Even if this ability to anaerobic paste for pasteurization is doubtful, anaerobic panning is widely used in practice because this method reduces the pesticide residue to a fairly stable form that can be used for landfill without causing significant contamination »Anaerobic Pauling is characteristically carried out in large containers in which a more or less thorough mixing takes place, either with the help of mechanical stirrers or through the recirculation of the sludge digester compressed gas.« Such mixing increases the sludge stabilization reactions very rapidly Formation of a large zone of active decomposition.

As indicated above, ₅ is the anaerobic Paulung generally at long retention or · Verweilteiten in the order of 20-30 days, without any heat supply to the system practiced wordene It has been found according to the prior art that increased facilitate mesophilic temperatures in the range from 30 ⁰ C to 40 ⁰ C the reduction of the Porderung in terms of the residence time to about 12-20 days "such a reduction of the treatment time is a Polge the fact that the size of the activity of the organisms, the which are highly influenced by the temperature and in the temperature range from 30 ⁰ C to 40 ⁰ C represent highly active mesophilic microorganisms the dominant microbial culture strain in the mud undergoing the Pauling process The mesophilic Paulung are in the range of about 35 ⁰ C to 38 ⁰ C with Minimum retention times of the order of 12-15 days "Temperatures up to 35 ° C increase the speed of panning and can lead to shorter retention times.

but at the expense of the functional stability of the system

long"

comparable during .Temperaturen below 35 ⁰ C longer Retenti.onszeiten

During anaerobic pelleting, methane gas is produced and used in characteristically in combustion heaters to compensate for the heat losses of the anaerobic potting system operating at an elevated temperature. Seasonal temperature fluctuations and fluctuations in the concentration of suspended pesticides in the sewage sludge, however, both have a significant impact the generation of methane gas as well as the amount of heat necessary to maintain the pumphead at the desired operating level of elevated temperature. If conditions of elevated temperature in the anaerobic pilling zone need to be maintained throughout the year, Polge provides an additional heat source In general, an essential element of the system of sludge digestion system _e

As the rates of anaerobic Paulung and the resulting rates of formation of methane gas. It is generally desirable to add sludge to the mud sludge tank as much as possible. Thus, the heat losses in the effluent will be greatly affected by the sludge content of suspended sludge exposed to treatment and by the temperature level in the scrubber zone stabilized sludge stream discharging from the anaerobic sludge digestion tank is minimized while maximizing the production of gaseous methane in the sludge digestion tank. However, even with such measures, increased temperatures in the anaerobic compaction zone are difficult In addition, even comparatively minor temperature fluctuations in

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the anaerobic zone of pumice results in a disproportionately serious disturbance of the process and in soaking of the content of the sludge digestion tank, as is well known

In the anaerobic Pauling process, the sludge solids that are subjected to the treatment undergo essentially three distinct successive stages of agitation: first, a period of solubilization, then a period of intense acidification (acidification), and finally we have it third, to do with a period of intensive digestion and stabilization (gasification). Each of these stages is characterized by the production of various intermediate and final products in the Pauling zone. Under normal working conditions, all three phases occur simultaneously the final gasification phase are methane and carbon dioxide, which normally make up more than 95 % of the evolved gas, with a methane content of 65-70 %. "The genesis of methane gas in anaerobic fermentation is due to the degradation of many compounds through numerous interdependent biochemical transformations that take place in a methodical and integrated manner." The complex organic species in the mud become a variant of ordinary Bacteria, the so-called acid-forming bacteria, converted into volatile acids and alcohols without the formation of methane · These products of the acid-forming phase are then converted into methane by another variety of bacteria 'known' as methanogens. «

The facultative acid-forming bacteria used in anaerobic sequestering are hardy and highly resistant to process changes in their environment. On the other hand, the methanogenic bacteria require anaerobic conditions and behave abnormally.

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extremely sensitive to process changes in their environment · For these reasons, no oxygen should be present in the anaerobic digestion zone. The inadvertent introduction of air into the sludge digestion tank will both adversely affect methane digestion and lead to a potentially hazardous situation due to the confluence of combustible methane gas with oxygen. In addition, the methanogenic bacteria will behave in such process conditions as, for example, pH Changes and Presence of Detergents, Ammonia and Sulfides, Sensitive In this regard, the temperature stability of anaerobic digestion zones is of particular importance _? The methanogenic bacteria required in the digestion process are highly sensitive to

, This leads to an insufficiently stabilized sludge and to a sludge product which, without further treatment, is not used for landfill or a similar one In addition, these methanogenic bacteria have a relatively low growth rate and such a factor causes the long retention times of

Due to this low growth rate, there is a danger of washing out the methanogenic organisms from the sludge digestion tank when the retention time of the sludge solids in the respective tank exceeds the lower limits described above Thus, because the anaerobic sludge digestion tank requires long retention times to ensure the presence of methanogenic bacteria, and the flow rate of the influent sludge to the digestion zone is generally quite low, the demands are

The capacity of the sludge digestion tank is very considerable. The operation at an elevated temperature is thus difficult, it requires a considerable supply of heat to the sludge digestion tank together with a precise control and regulation of the temperature of the sludge digestion tank. As discussed above, the process according to the prior art State of the art, taking into account these considerations, made use of the methane gas produced by the anaerobic Pauling process * This gas was used as a fuel for the sludge digester to maintain a constant elevated temperature even under extreme ambient temperature fluctuations. "Such use of the methane gas has become 'proved to be effective in minimizing the great need for the heat energy process''.

As an alternative to the preceding methods, the biodegradable sludge can be digested under aerobic conditions. "Purely these purposes have been used in practice in general as an oxidizing agent. It is known that aerobic precipitation is faster at elevated temperatures." If the temperature rises above 35 ° C addition, the entirety of mesophilic microorganisms decreases and the thermophilic Pormen take _e The temperature range of 45 ⁰ C to 75 ⁰ C is often considered the thermophilic region in which predominate the thermophilic bacteria, and most mesophilic bacteria are dead, "About this range take the thermophilic bacteria and at 90 ⁰ C, the system is essentially sterile · Because of the rapid oxidation of the sludge is biologically abbau.baren more complete removal in the thermophilic Paulung of volatile suspended solids achieved as during the same period of Paulung at ambient temperature · A more stable residue is recorded, which without further. Discomfort can be eliminated. It is also proved that the thermophilic coloring agent effectively removes pathogenic bacteria

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2 03 442 - reduce or eliminate sludge, thereby avoiding potential health hazards associated with sludge removal ·

When diffused air systems are used to deliver the oxygen to the tank, the air passes through the bulk of the slurry in a sludge digester and releases freely; to the atmosphere, the heat losses of the sludge with heat release to the air passing through the sludge digestion tank tend to assume substantial values. As a result, aerobic filtration using air has typically been associated with mesophilic clumping to date Microorganisms are met © air systems are generally not used to carry out the thermophilic .Paulung 'unless there is significant heat energy available without difficulty to maintain the temperature of the sludge in the sludge digester in the thermophilic temperature range Such a situation may occur, for example the potting system is in the immediate vicinity of a power plant producing large amounts of waste heat so that such heat energy is essentially "free" for use in the potting plant. The air only has 21 % oxygen and only sth A 5-10 % of the oxygen content is derived from it. As a result of this, a very large amount of air has been used to meet the oxygen demand and the sensible heat of the "spent" air and the latent heat required to consume the spent air saturating with water vapor are essential * As a result of these heat losses during air digestion, the effects of autothermal heat are generally insignificant and very large amounts of external heat are needed to keep the temperatures at the advantageous levels *

It is known that the heat losses in aerobic panning are / is greatly enhanced by the use of an oxygen-enriched

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If the oxygen is used effectively, the amount of gas j which must be supplied to and discharged from the sludge dewatering tank is considerably smaller compared to the corresponding amount of air, because a large amount of nitrogen or total nitrogen has been removed beforehand. The heat losses due to the sensible heating of the gas and the evaporation of water into the gas are reduced. These reductions in heat losses are sufficient for the autothermal heat alone to maintain the temperature at such a level. which is considerably above the ambient temperature level, so that the Paulung®one is able to work effectively in the thermophilic temperature range, with little or no external heat being taken to maintain the Pauling process. Since the thermophilic stabilization is much faster than the meso In the aerobic zone, the required dwell time in the aerobic zone is reduced to a high degree in accordance with the thermophilic procedure. This, in turn, allows the use of smaller basins, thus reducing heat loss reduced to the environment. Due to the faster rate of oxidation of the sludge, the thermophilic aerobic treatment may suitably contribute to a high reduction of biodegradable, volatile pesticides. Eo is, for example, reductions in pesticides of the order of 80-90 % with comparatively short sludge retention times of 3 up to 10 days «

In view of its essential attractiveness, thermophilic aerobic precipitation has several associated disadvantages in relation to anaerobic precipitation. Since the thermophilic aerobic panning process is intrinsically oxidative,

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In this process, a gas is initially produced as bio-oxidation reaction product which contains carbon dioxide and water vapor which can not be used further _f but rather be discharged into the atmosphere in a desirable manner. In contrast, during the anaerobic digestion, methane gas is produced which acts as reaction by-product This "gas can be taken from the treatment plant and is also suitable as a heating gas to meet the heat energy needs associated with digestion at elevated temperatures." In addition, the aerobic fumigation zone requires much greater mixing and gas / slurry contact effort than is necessary in the anaerobic digestion system for mixing the contents of the sludge digestion tanks _e

The aim of the present invention is to present an improved process for sludge digestion «

The invention has for its object to provide © in sludge digestion processes under aerobic / anaerobic conditions, which meets the increasing wastewater disposal while complying with environmental protection regulations and which is suitable for eliminating the sludge solids more economically and γ / more effectively than hitherto. »

With short locations, the sludge digestion process of the present invention can be characterized by the following steps: introduction of the sludge and aeration feed gas consisting of at least 20% vol. Oxygen into a first digestion zone and mixing of the constituents in this first digestion complex in sufficient quantity and speed to

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aerobic sludge sludge while maintaining the total sludge content of suspended solids (MLSS) v / enigatens of the order of 20,000 mg / l and the temperature of the sludge in the range of 35 ⁰ C to 75 ⁰ C in the first digestion zone _e

The previous aerobic digestion is continued during a Schlainmjjetentions · "residence time (duration) of 4 to 48 hours for the purpose of partially reducing the content of sludge to biodegradable, volatile, suspended solids, which was fed to the first digestion zone, the partial stabilized sludge is discharged from the first digestion zone. This discharged and partially stabilized sludge is then anaerobically digested in a closed, continuous digestion zone while

the temperature of the sludge in this second digestion zone is maintained in the range of 25 ^° C to 60 ^° C while maintaining a sufficient solids retention time (duration) to further reduce the sludge content of biodegradable, volatile, suspended solids to less than about To obtain 40 % of the sludge's content of biodegradable, volatile, suspended solids fed to the first digestion zone, producing methane gas. The still-stabilized sludge and methane gas are discharged from the second digestion zone. " ,

The term "slurry" as used herein means a mixture of solids and a liquid characterized by a solid phase and a liquid phase associated therewith, the solids being at least partially biodegradable, ie, they Biodegradable Mud Masses are generally characterized according to their content of Biodegradable, Volatile, Suspended Solids (BYSS) and also by their Volatile Suspended Solids (VSS) content, the latter parameter includes both biodegradable and non-biodegradable volatile suspended solids. As used herein, "biodegradable, volatile, suspended solids content" is essentially the maximum reduction in solids content It can be reached by aerating the sludge with an oxygen-containing gas at ambient temperature, for example at 20 ° C. In this connection, it is assumed that the maximum reduction of the solids content is achieved after aeration period of 30 days * Specifications for such a determination are given in the book by YLW · Eckenfelder and

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D.L. Ford, entitled "Control of Water Pollution", The Pemberton Press, 1970, page 152. · By determining the VSS values for the fresh mud and analog values after aeration time of 30 days, the biodegradable fraction of the total VSS content can be calculated as follows:

VSS (fresh) - YSS (after 30 days) VSS (fresh)

As used herein, VSS of a sludge means the volatile sludge content of the sludge as determined by Examinations 224A. and 224B in the "Standard Methods for the Examination of Water and Wastewater", 13th Edition (1971), published jointly by the American Society for Health Care, by the American Waterworks Society and by the Association for the Control of Water Pollution, on the pages 535-536 * The term "stabilized sludge" refers to a sludge having a reduced content of biodegradable, volatile, suspended pesticides following a pumice treatment and as a result of such purging treatment. "Slurry retention time" means average duration as used herein during which the sludge is in a given zone of compaction. "The calculation of this retention time is carried out according to the following formula:

in which; T '. = Mud retention time (in days or hours); V -, '= sludge volume in the pilling zone during treatment (in ft); and

Q ₀ = volume flow velocity of the sludge

3 at the delivery to the Pauling zone (in ft / day

or in ft / hour).

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As used herein, the term "aerobic digestion" means the biodegradation of the sludge solids. * This digestion is carried out under the action of aerobic microorganisms. Such digestion requires that oxygen be dissolved in the liquid sludge phase so that it can be absorbed by the microorganisms available in the slurry is _e the dissolution of the oxygen must be in a sufficient quantity and velocity such that the oxygen demand for biodegradation will speak corresponds * According used herein, the language, the expression "mixture of the sludge and the aeration feed gas in an amount sufficient means and Sludge aerobic digestion rate "either an oxygen enrichment of the sludge at a rate at least equal to 10 % of the value of the empirically determined specific acid uptake rate (SOUR), determined according to A process, which will be explained in more detail below, or an oxygen enrichment of the sludge with the relative amounts of aeration feed gas and wherein the sludge and aeration rate are sufficient to recover at least 0.03 lbs of oxygen per lb of volatile, suspended solids in the sludge Or it is any suitable alternative quantitative determination of the sludge / aeration feed gas ratio during the contact step, sufficient to ensure the presence of aerobic digestion in the first digestion zone. "This then corresponds to the definition aerobic digestion according to the explanation given above.

In the expression of the specific rate of acid intake, the requirements for the enrichment of the sludge with oxygen, which is necessary for the aerobic digestion, suitably in accordance

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The sludge to be treated flows through a small test vessel at a sufficient volumetric flow rate to reach the predetermined sludge retention time required for the sludge retention time © has been selected, the aerobic digestion This retention time for the aerobic digestion is according to the invention in the range of 4 to 48 hours _e where contact of the sludge takes place with a ventilation gas comprising at least 50 vol »-% oxygen · the aeration is performed in such a manner by a Concentration of dissolved oxygen (D "0 _e ) of at least 2 mg / l in the sludge is maintained, as measured by any suitable DO ₀ measuring probe of known type. During the aerating, the sludge in the test vessel is kept at the predetermined temperature, excl Selected for the aerobic Pau-This temperature corresponds to the invention

aerobic Paulung the range of 35 ⁰ C to 75 ^D C · The foregoing experimental treatment of the sludge, wherein a dilution of the incoming sludge in the test tank with tap water to obtain the required D _e 0. value of at least 2 mg / 1 be necessary can , is carried out until a stationary condition is reached »To achieve such a condition, a longer operation of the experimental system on the order of, for example, 5 to 7 days may be necessary«

After obtaining steady-state working conditions in the experimental system, a measured sludge sample is taken from the test vessel and aerated rapidly, while maintaining the temperature of the sample taken at the previous value in the test vessel. The aeration is carried out, for example, by vigorous stirring of the sludge the aeration gas, which is at least 50 vol% -%

The slurry is stirred to increase the De 0 value of the aerated sludge to about 7.0 mg / l. At the point where the dissolved oxygen concentration is about 7.0 Subsequently, during the subsequent decrease, the dissolved oxygen concentration in the sludge is decreased from the value of about 7.0 mg / 1 at the completion of the aeration down to the substantially negligible dissolved oxygen concentration is the time required to decrease the dissolved oxygen concentration from 6.0 mg / 1 to 1.5 mg / 1ffl. the sludge sample is then calculated by measuring the change in the dissolved oxygen concentration during the period of the measurement, ie _e , 4.5 mg / l (= 6.0 mg / l -1.5 mg / l) , by the time, the e In order to reduce the dissolved oxygen concentration from 6.0 mg / 1 to 1.5 mg / 1, the following is calculated: · From the resulting OUR value, the specific oxygen uptake rate (C30UR) is calculated as follows: the OUR value in units mg / 1 / time is divided by the concentration of the sludge sample in mg / l _e The SOUR value thus indicates the units mg of oxygen / time / mg of pesticides per _e

Based on the previous calculation of the SOUR parameter for the sludge to be treated, the amount and rate of oxygen transfer from the oxygen-containing aeration gas to the sludge during the aerobic digestion of the present process can be determined * to now accommodate the respiratory demand (acid consumption) of the sludge for the aerobic digestion, on the basis of considerations to obtain an adequate stabilization of the sludge during the aerobic digestion before the subsequent anaerobic digestion, the enrichment of the sludge with

Oxygen in the first buffing zone in the present process may be carried out at a rate at least equal to 10 % of the empirically calculated SOUR value. Under preferred practical conditions, such sludge enrichment must be carried out with oxygen at a rate which is at least equal to 50 % of the empirically calculated SOUR value *

Alternatively, the following possibility may be provided. Based on the considerations of the amount of oxygen required to biodegrade a unit of volatile suspended solids in a given sludge, as determined for sludge types having different characteristics, mixing must be carried out of the sludge and the oxygen-containing aeration feed gas for the purpose of carrying out the aerobic treatment in the first composting zone in the method according to the invention with the relative amounts of aeration feed gas and sludge and at the aeration rate sufficient to obtain the useful application is the ingestion of at least 0.03 lbs of oxygen by the sludge per pound of volatile suspended pesticides in the sludge fed to the aerobic pudding zone * The minimum value of such a contact ratio is at a threshold associated with the aerobic precipitation necessary to ensure adequate stabilization of the sludge in the first competing zone of the process of the invention before subsequent anaerobic precipitation. In practical conditions, it is generally desirable to enrich the sludge with oxygen at the relative proportions of Sufficient sludge and aeration feed gas and at the aeration rate sufficient to obtain the utility · It is the uptake of 0.1 to 0.35 lbs of oxygen by the sludge per lb of the volatile, suspended pesticides in the sludge that is the sludge

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In general, such gas / sludge contact ratios offer the possibility that the content of volatile suspended particulate matter in the sludge fed to the first composting zone in the present process is aerobic by about 5 to 20% % is reduced in the first Paulungszone "in general, the content of volatile suspended Peststoffen in the slurry, the der.aeroben Paulungszone'zugeführt is reduced desirably at least 5% in this Paulungszone to a partially stabilized sufficiently • Such a minimum level of partial stabilization is particularly desirable, so that the anaerobic treatment is adequately "buffered" against aerobic deterioration due to procedural disturbances due to changes in the environmental conditions Type and condition On the other hand, in the course of treatment in such a panning zone, the reduction in the content of volatile, suspended pesticides in the feed slurry supplied to the aerobic potting zone is desirably set at a value of

, about 20 % or less in order to fully realize the synergistic ¥ or ™ parts of the present invention. More will be said about such advantages in detail below, and this is an unexpectedly high total production of methane gas in the second anaerobic Pauling treatment in Relationship to a known Anaerobic Pauling System "As a balance of the foregoing considerations, it can be said that the mixing of the aeration feed and sludge in the first buffing zone in the most preferred manner with the relative amounts of aeration feed gas and sludge and at the aeration rate It is sufficient to obtain the usefulness of the sludge

thereby absorbing 0.15 to 0.25 lbs of oxygen through the slurry for each lb of volatile, suspended solids in the slurry fed to the first digestion zone.

As used herein, the phrase "anaerobic digestion" means the biodegradation of the solids in a slurry, which is carried out without free oxygen. "

The present invention is based on the surprising discovery that an aerobic digestion zone operating at the thermophilic or near thermophilic temperature range can be advantageously integrated with a downstream anaerobic digestion zone to permit partial digestion of the sludge in each of the subsequent zones and that such integration contributes to a substantial improvement in the process beyond that which would be expected, one bases the considerations on the respective digestion treatments when they are carried out separately, as will be explained below.

In the prior art process, no attempt has been made to combine aerobic and anaerobic sludge digestion at elevated temperature in the manner contemplated for numerous reasons according to the present invention. First, the capacity is the container in connection with the anaerobic digestion process according to the further above discussion extraordinarily large and it has been found necessary _s large quantities of methane gas to produce for heating purposes in order to ensure efficient operation of the giant digester · the combination of an anaerobic sludge digester with a aerobic digestion stage would thus, in view of the consideration of the requirements for the overall

The capacity of the containers for the combined process would appear to be undesirable. It would be expected that the requirements for the capacity of the containers would be greater than for the capacity to associate with each individual Pauling process alone. Such a combination would appear just doubling first glance, the punctures that edem aerobic and anaerobic Paulungsprozesse normally associated with j in increased equipment costs without due advantage in terms of the efficiency of treatment "

In addition, the combination of an anaerobic sludge digestion tank with an aerobic pilling stage would appear to be undesirable due to the expected inability of the anaerobic potting treatment to provide only a partial pumination treatment of the sludge in the combined system, with sludge retention times (duration) among the long retention times As has been stated above, long residence times during anaerobic treatment are necessary in order to obtain efficient production of methane gas and adequate sludge stabilization. anaerobic conditions below their normal value according to a full treatment in a combined aerobic / anaerobic Pauling process would have been reduced, to ensure that only partial Paulung during anaerobic treatment it is to be expected that there will be an excessive depletion of methanogenic bacteria during the anaerobic treatment stage with a short residence time, due to the loss of these slow growing species in the effluent from the sludge digestion tank, with a consequent inadequate sludge stabilization in the combined process *

In addition to the previous reasons, the combined would

aerobic / anaerobic panning systems appear disadvantageous from the point of view of operational stability, since each of the aerobic and anaerobic potting treatments alone requires exact control and regulation of the operating temperature when operating at elevated temperatures, so that the coupling of the two potting processes in question is such Would require an even more precise temperature control, taking into account the possibility of increased adverse effects due to temperature instability and variability.

Finally, a combined aerobic / anaerobic potting system would be detrimental in considering the possibility of carryover of dissolved residual oxygen from the first aerobic treatment stage to the downstream second anaerobic treatment stage of the process. As stated above, the methanogenic bacteria, are found to be of strictly anaerobic character and are extremely sensitive to changes in their environment. "It is well known that any significant introduction of oxygen into the anaerobic Pauling zone adversely affects sludge stabilization through methane formation and thus the risk of oxygen evolution from the liquid into the methane-containing gas phase and the formation of a combustible gas mixture in the sludge digestion tank will cause »

In contrast to the previously anticipated behavior, it has unexpectedly been found that the use of a thermophilic or near-thermophilic aerobic zone in front of a mesophilic or thermophilic anaerobic zone and the operation of these treatment zones in accordance with the method of the present invention not only provide a workable and economical sludge treatment system. but also to a pilling system with unique

These improvements are attributable to the synergism that is achieved between the aerobic and anaerobic Pauling zones in the current process. For example, the inventive method is capable of providing thermal stability in operation to the total sludge digestion system that can not be achieved in each working Paulungsstufe «. In addition, the integrated panning method of the present invention provides a highly stabilized sludge, despite a marked reduction in sludge retention time for the overall process over the duration that would be expected based on the anticipated additional retention time requirements for the partial pumice treatments of the individual components It is surprising in this respect that the anaerobic pilling zone in this process is capable of operating at sludge retention times that are significantly shorter than those required for complete stabilization treatment of the sludge in known anaerobic sludge digestion tanks used alone work, and that such an operation is achieved without loss of efficiency in terms of utility or treatment _? As would be expected "As an example of retention times suitably utilized in the present invention, a system of pilot plant embodying the present inventive method is satisfactorily at a mud retention time in the first aerobic panning stage of 24-48 hours and a retention time (duration) in the second anaerobic Paulungsstufe operated from 4 to 5 days * The foregoing advantages are in the present invention, together with a substantial reduction in the requirements for the fit or ". Absorbance of the system in relation to a known anaerobic

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Mud septic tank system realized, but taken while maintaining an unexpectedly large proportion of methane production of the known anaerobic sludge digestion tank on its own * This will be further detailed below. For example, the system of the present invention can use about 60 % of the capacity required by the prior art anaerobic puming system. However, about 75 % of the methane gas production capacity of the latter system can be maintained. The present inventive method results "Polge results in a significantly greater amount of exhaust gases having a high methane content for onward transport from the sludge digestion plant relative to the anaerobic potting system according to US Pat Finally, in the present process, there is no significant carry-over of oxygen from the first zone of incineration to the first zone; Gas phase of the second zone of

The reasons for the unexpected advantages according to the present invention as described above are not fully understood. However, there is a likelihood that the lack of significant carryover of oxygen from the first panning zone to the second pilling zone is attributable to the unexpectedly high rate of oxygen uptake of the sludge in the first pilling zone, which contributes to rapid and complete depletion of any dissolved oxygen in the mud which passes from the first zone to the second zone before any appreciable evolution of dissolved oxygen into the gaseous phase can occur in the second zone. "The impressive, low sludge retention times (duration) in the current method, especially in the anaerobic treatment, can be combined with the for the procedure

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characteristic thermal stability and unexpectedly high methane production during anaerobic treatment are the result of chemical or biological acclimatization of the sludge and microorganisms in the aerobic zone, thereby increasing the efficiency of subsequent anaerobic treatment "nothing" -not least, we do not have the desire to be bound by any particular theory for explaining such process, and consequently, the above statements are not to be construed in any limiting sense to the present invention. Only the essential steps and features which are to be considered described and claimed herein. "

The invention will be explained in more detail with reference to embodiments pointers in the following In the drawing,

FIG. 1j shows a schematic flow diagram of a digestion process according to an embodiment of the invention, in which heat is recovered from the outgoing media from each of the first and second digestion zones; FIG.

Fig. 2; represents a schematic flow diagram of a digestion process according to another embodiment of the invention, wherein oxygen-depleted digestion gas, which passes from a closed first digestion aone for discharge, in a secondary loading. : action oxygen uptake of water with the bio ~ chemical oxygen demand is utilized?

Fig. 3: corresponds to a schematic flow diagram _? according to a still further embodiment of the invention, wherein the sludge is from the pri ~?

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and secondary effluent treatment stages are directed to the sludge digestion zones

Fig. 4: shows a graph of the temperature profile of the incoming sludge in the first. Faulungszone is necessary to maintain an operating temperature von'50 ⁰ C in the first Faulungszone plotted as a function of the total content of suspended solids (MLSS) in the in the first Faulungszone 'inflowing sludge?

5 × corresponds to a schematic flow diagram of yet another inventive embodiment, where

with a smaller part of the sludge flowing into the process system being diverted into the second digestion zone *

We are dealing now with Figure "1 _e It is a schematic flow diagram of a method according to an embodiment of the present Brfindung _e Such a method is suitable for the treatment of sludge in a thermophilic or nearly thermophilic aerobic first Faulungsstufe, followed by a subsequent mesophilic anaerobic digestion The sludge may originate from a primary sedimentation tank, from the clarifier of an activated sludge wastewater treatment plant or from a trickling filter or from any other sludge-producing system. This sludge enters the treatment process through the supply line 8 and is subsequently heated in the heat exchangers 22 and 15, for example to a temperature of 30 ⁰ C to 35 ⁰ C. This heating occurs before the introduction of the sludge in the first digestion zone 10 to the temperature in the digestion zone iia range from 35 ° C to 75 ° C and

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preferably maintain in the thermophilic range of 45 ⁰ C to 75 ° C * The slurry in the supply line 8 sprioht its temperature on the ambient temperature "He is first heated in the heat exchanger 22, through © inen passage of that sludge in an indirect heat exchange in countercurrent with the still stabilized sludge _? the sum via the feed line 24 from the closed second Paulungszon © 20 discharge reaches "In this manner, heat from the further wiedergewönnen stabilized sludge and the resulting, cooled, stabilized sludge passes from the Wärmeaustauscher22 for discharging and over the managerial

25 for final disposal or for the purpose of other end use. The still stabilized sludge entering the heat exchanger 22 via the supply line 24 may suitably have a temperature of 35 ⁰ C to 40 ⁰ C, so that the incoming sludge leaving the heat exchanger on the line 9, to a temperature is heated from 28 ⁰ C to 30 G "via the line 9, the partially flowing slurry heated further in -the heat exchanger 15 to a temperature of 30 ⁰ C to 35 ⁰ C is heated, by indirect countercurrent heat exchange with the partially stabilized sludge which has come from the first Paulingzone 10 via the supply line 14 for discharge and passes through the heat exchanger via the line 16 to the second Paulungzone 20 ·

As an alternative to the above-described interchange of heat with the sludge product flow rates from the respective scrubber zones, the incoming sludge may be heated prior to introduction into the first scrubber zone by indirect heat exchange with a suitable externally supplied heat transfer medium, such as steam or hot water Although heat recovery from the warm mud product flow rates from the respective Pauling Zone is preferred, this method of heat recovery effectively serves to maintain heat within the process and minimize the thermal energy requirement for the process. Although heating of the incoming sludge prior to its introduction into the first compaction zone is of no significant importance in the broad practical application of the present invention, under practical conditions it may be desirable to maximally improve the thermal efficiency of the process at elevated temperature Desirability of such heating of the sludge, as will be discussed below, depends on the level of pesticides in the sludge

of sludge retention time in the aerobic zone and other procedural parameters *

The still heated sludge discharged from the heat exchanger 15 via the supply line 11 is supplied to the first compaction zone 10 together with the aeration feed gas via the supply line 17 as flowing media of the process to the first purge zone. The aeration feed gas in the supply line 17 is minimized at least 20 VoI ₄ * -% oxygen, at least 50 Yoi · - $ oxygen and desirably at least 80 vol _e ~% oxygen in the vent feed gas to be preferred in order to suitably high mass transfer driving force and a high rate of oxygen to The supply line 17 has a connection to a source of the oxygen-containing aeration feed gas (not reproduced), which may for example consist of a compressed air supply system, or if that Preferably, venting gas having a high oxygen content, the source for the production of such aeration feed gas may suitably consist of a cryogenic oxygen plant or supply tank or an adsorption air separation rocket at adiabatic pressure ratios, as known in the art as supply sources for a oxygen-enriched gas is available «. According to the representation, the oxygen-containing aeration feed gas can also be heated via the supply line 1.7 by a heating device 19 in order to assist in maintaining the temperature in the panning zone 10 at the desired process level. In the general practice of the invention, air or other aeration feed gas may be used a low oxygen content, ie, with 20-50% by volume of oxygen, be terminated in a suitable manner if the autothermal heating of the sludge

2 08 442 _

in the aerobic digestion zone is not required to maintain the temperature in this zone of digestion in the required range of 35 ° C to 75 ° C, provided that a large source of externally supplied heat energy available for the heating of the sludge As already mentioned above, the heat losses due to the air (or in the presence of another low oxygen content venting gas) tend to be very large so that a vent feed gas has at least 50 VpI.-% oxygen and desirably with at least 80% by volume of oxygen is preferred to assist autothermal slurry heating in the aerobic digestion zone. The amount of oxygen-depleted digestion gas is then minimized is drained from such a digestion zone and otherwise emits heat energy from the process system. In addition, a high oxygen content vent feed gas containing at least 50 vol.% oxygen is preferred to increase the amount of oxygen transfer from the vent feed gas to the sludge during aerobic digestion and thereby allow for more intensive aerobic digestion than is achievable with the low-oxygen aeration feed gas. "Regardless of whether a high or low oxygen (as defined above) aeration feed gas is used in the aerobic digestion zone In the present process, it is generally preferred that the aerobic digestion zone be closed with a lid to form a headspace overlying the sludge and from which the deoxygenated waste digestion gas can be discharged Possibility to perform a controlled discharge of the exhaust gas, for example by means of a small vent pipe through the cover and under

Combination of the gas space with the external gas environment "This results in a heat retention in the aerobic Paulungszone in relation to an open Paulungszone, the oxygen-depleted aeration gas has the opportunity to freely emerge from the treated sludge volume in 'the outer gas environment, d ho, in the ambient atmosphere «. Where a high oxygen content aeration feed gas is used in the aerobic Pauling Zone, it may be desirable to provide a lid for the Pauling Zone to form a headspace from which the oxygen-containing aeration gas may be recycled to the sludge, for example Returning the gas from the overhead gas space to an underwater blasting apparatus or allowing the sludge to recycle to the vent gas, for example by means of a surface aeration device. Such arrangements for recycling the aeration gas or sludge into the circuit provide the opportunity in that the aerobic potting treatment helps to realize a high utilization of the oxygen content in the aeration feed gas supplied to the aerobic pumice zone »

In the aerobic pumphead zone 10, the flowing media consisting of the slurry and the aeration feed gas are mixed together. If the potting zone 10 is closed with a lid and a high oxygen content aeration feed gas is used, one of the flowing media, the sludge or the aeration feed gas, desirably according to the embodiments set forth above, and simultaneously with the mixing of the substances with the other flowing medium in the Pauling zone in sufficient. The amount and rate of aerobic digestion of the sludge can be recirculated while keeping the total sludge content of suspended sludge (MLSS) at least 20000 mg / 1. "Such mixing and recirculation of flowing media in the sludge Circle-

Run is suitably effected by the stirrers 12, which under practical conditions may consist of an underwater turbine blasting apparatus and a gas compressor, the gas compressor having a connection to the gas pressure space in the panning zone and to the gas blasting apparatus to discharge the oxygen-containing aerating gas Recirculating sludge, or alternatively, the agitators 12 may consist of a surface aeration device for returning the sludge to the aeration gas in the gas pressure space of the potting zone 10. The recirculation of one of the flowing media, sludge or aeration feedgas, with respect to the other Medium in the aerobic digestion zone may, according to the statements made above, be considered desirable under practical operating conditions where a high oxygen content vent feed gas However, such recirculation of materials into the cycle is not essential within the broad practical application conditions of the present invention, and is not essential to achieving high levels of oxygen dissolution in the sludge and high utilization of the oxygen contained in the aeration feed gas In some cases, it may be possible to achieve adequate dissolution of the oxygen in the slurry and high utilization of the oxygen in the aeration feed gas in a single pass of the aeration feed gas through the aerobic potting zone. The relative proportions between the aeration feed gas and the slurry to be contacted in the first. The Paulungszone for the aerobic Paulung in this zone can be suitably set in the manner as described in the preceding summary · The basis for this example, for example, an empirical determination of the specific oxygen take-up rate (SOUR) of the sludge to be treated or the amount of oxygen that is required

In some systems, it may be desirable to detect the presence of intense aerobic precipitation in the first composting zone by maintaining high levels of dissolved oxygen (DeO.) in the sludge in the sludge For example, it is at least 2 mg / l but generally. the oxygen uptake rate of the sludge in the first process of the present Paulungszone sufficiently high so that the Aufrechterhai tung a significant concentration in the D.0 _e to be enriched with oxygen for effective sludge aerobic Paulung is not necessary _e

In the aerobic Pauling zone, the total sludge suspended solids content (IiLSS) is maintained at least at 20,000 mg / l to thereby maintain the high sludge temperature in the first pilling zone. This is necessary to achieve a satisfactory level of partial sludge stabilization in the aerobic Paulungszone with short retention times (duration) *

Among the preceding process conditions of the mud in the first Paulungszone for Paulung at a temperature in the range of 35 C to 75 ⁰ C and preferably in the thennophilen range from 45 ° C to 75 ⁰ C is maintained in order of a rapid biodegradation to get content of the sludge volatile suspended Peststoffen "in this regard, it is appreciated that the aerobic Paulung can be in the almost thermophilic temperature range from 35 ° C to 45 ⁰ C are suitably used in the context of extended practical use conditions of the present invention, in order to arrive at degradation rates of the pesticides which, although not as fast as the rates characteristic of the thermophilic process, are sufficiently high to provide adequate sludge stabilization in the leachate.

sludge retention times characteristic of the first purging treatment in the current process.

The aerobic pumeration treatment is continued in the first pilling zone for a mud retention time (duration) of 4 to 48 hours to partially reduce the content of biodegradable, volatile, suspended pesticidal sludge fed to the first pilling zone. As previously mentioned Preferably, the aerobic pumination treatment is preferably carried out to reduce the sludge content of volatile suspended solids fed to the first panning zone by from 5% to 20 % for reasons already discussed above. In the case of aerobic pumination, the sludge retention time (duration) is at least equal to 4 hours in order to achieve a sufficient degree of partial stabilization in the first pilling zone. At retention times below 4 hours, the amount of sludge stabilization required in the subsequent anaerobic treatment is disproportionately large ß in relation to the stabilization level during the aerobic first treatment and the retention time of the entire system and the requirements in terms of capacity begin to approximate those demands of the known anaerobic Paulungssystems, with an increasing loss of unexpected improvement in these process variables (d » h, retention time of the entire system and passability). The typical residence times in the course of the aerobic panning treatment range from 4 to 48 hours. · For similar reasons, the sludge retention time in the aerobic potting zone must not exceed 48 hours. · Beyond such value, the amount of sludge stabilization in the aerobic potting zone becomes unduly large on the residual stabilization in the subsequent anaerobic treatment, so that

the methane gas production in the latter treatment stage has a tendency to be disadvantageously lowered in a serious way _e And again, there is an increasing loss of the unexpected improvement in the retention time of the overall system and the requirements of the Passungsvermögen, accessible in connection with the sludge retention time during the aerobic Paulung in the range of 4 to 48 hours _e Preferably, the retention time (duration) in dem'Bereich 12 to 30 hours, and suitably in the range of 12 to 24 hours "the preceding considerations underlying

Following the aerobic pumination treatment described above, the partially stabilized sludge from the aerobic zone-via line 14 and the oxygen-depleted Pauling gas separately is discharged from the aerobic zone via line 18. "In the Palis, where the aeration feed gas is supplied to an oxygen content of at least 50 % by volume of the first Pauling zone, the oxygen-depleted Pauling gas discharged from the aerobic Paulungszone desirably contains at least 21% by volume of oxygen to produce a suitably high utilization of the oxygen contained in the aeration feed gas, while maintaining the energy expenditure for the contact between the aeration gas and the sludge at a suitable, low IT level, for the purpose of an economic procedure "In order to ensure high oxygen utilization, in particular if be a ventilation The oxygen content of the exhaust gas from the Pauling zone via the conduit 18 can be readily maintained at a suitable level by controlling the relative rates of introduction of the venting gas via the supply duct 17 and venting over the gas Line 18 are suitably regulated «. For example, gas streams are used for this purpose.

control valves either in the inlet gas supply lines or in the exhaust pipes, with the participation of an analyzer for analyzing the purity of the oxygen (not shown) located in the exhaust pipe 18 in such a manner as those skilled in the art are, well known ·

It has now been determined that at Aufrechterhaltung.des sludge in the aerobic Paulungszone according to the present invention on a thermophilic temperature of at least about 50-52 ⁰ C is reached a substantially complete pasteurization of sludge "In the context of the extended practice of the present Invention, the partially stabilized sludge is discharged from the aerobic Paulionsaone 10 via the line Ή at a temperature in the range between 35 ° C and 75 ⁰ C. Insofar as this specific embodiment of the invention makes use of mesophilic anaerobic digestion in the closed second compaction zone 20, For example, heat may desirably be withdrawn from the partially stabilized sludge via line 14 to ensure efficient drainage of the anaerobic sludge treatment at a lower temperature than that used in the first bump zone 10 the sludge via the feed line 14 flows through the heat exchanger 15 in indirect one. The cooled, partially stabilized, aerobically treated sludge then flows through the supply line 16 into the closed second compaction zone 20 *. There is an alternative to this In doing so, the partially stabilized sludge in the conduit 14 could be cooled by an externally supplied coolant. For this purpose, a treated effluent from a wastewater treatment plant could be used * In addition, there may be no need to use heat exchange during the winter, such as

-3S-

This is done through the heat exchanger 15 to cool the partially stabilized sludge * Here, the heat losses to the environment from the second zone and the flow of the sludge from the first to the second Faulungszöne satisfactorily compensate for the lack of such a heat exchanger.

The partially stabilized sludge is held after entering the second Paulungszone via the supply line 16 in this zone under anaerobic conditions at a temperature of 25 ⁰ C to 45 ⁰ C while maintaining a sufficiently long Sehlammretentionszeit (duration), to further reduce the The content of biodegradable, volatile suspended solids sludge in the sludge may reach less than about 40 % and preferably less than 20% of the sludge's content of biodegradable, volatile, suspended pesticides fed to the first pilling zone, with the addition of methane gas form _e

In the context of the extended practice of the present invention, the temperature of the slurry in the closed second Paulungszone is maintained in the Beer calibration of 25 ⁰ C to 60 ⁰ C * This temperature range includes both the workflow in the mesophilic range of 25 ⁰ C to 45 ⁰ C. and the operation flow in the thermophilic range of 45 ⁰ C to 60 ⁰ C. Pur the purpose of an effective highly workflow is the anaerobic mesophilic Paulungszone during operation on a sludge treatment temperature between 35th ⁰ C and 40 C, and preferably maintained between 37 ° C and 38 ⁰ G. A preferred operating temperature range for the anaerobic thermophilic digestion extends von.45 ° C to 50 ⁰ C. An operation in the foregoing preferred temperature ranges produces a particularly rapid degradation of the biodegradable, volatile solids by the microbial culture strains which come into embossing therefor "

- 33 -

In the operation in the anaerobic digestion zone 20, the contents of this zone are mixed in an advantageous manner continuously by stirring devices 21. This creates a large zone of active degradation and a significantly increasing rate of stabilization reactions. The residence time of the sludge in the second panning zone may suitably be in the range of 4 to 12 days and preferably in the range of 5 to 9 days. Sludge retention times (duration) in the second panning zone of less than 4 days may be undesirable because retention time tends to become increasingly inadequate to support a large viable population of methanogenic bacteria during anaerobic treatment, with an adverse effect on the overall sludge stabilization of the potting system. On the other hand, with sludge retention times in the anaerobic zone of more than 12 days, the retention time for the second panning zone becomes unnecessarily long and it becomes increasingly difficult to obtain the benefits of synergistic retention time and pilling requirements associated with the present invention integrated method in the extended retention range of 4 to 12 days can be achieved.

After the completion of the anaerobic treatment of the sludge in the second zone of the zone 20, the resulting, still stabilized sludge from the second shade of honeys becomes. discharged via the line 24. There is a corresponding heat exchange in the heat exchanger 22 for the recovery of Y / through the incoming sludge before the final discharge of the sludge from the process via the line 25. The methane gas formed in the second zone 20 as a product of the biochemical reactions in this zone is discharged from the anaerobic treatment via line 23. In this line 23 is a flow control valve 26 *

2 08

As discussed above, the continuous operation of an anaerobic sludge digestion vessel at high flow rates and at optimum temperatures above ambient has been difficult to maintain within known practical service conditions of the internal door. Variations in ambient temperature typically cause a change in both temperature "Such temperature fluctuations, as discussed, affect the relative rates of growth of the acid-producing and methanogenic bacteria." The acid-producing bacteria are typically very hardy and moderately strong Temperature fluctuations do not change their metabolic activity to any significant degree. On the other hand, the methanogenic bacteria are extremely sensitive to environmental conditions. If the maintenance of a constant temperature in the anaerobic fouling zone is disturbed by even slight temperature fluctuations, there is a high probability of instability in the activity and growth of the methanogenic bacteria. As a result, the activity of the acid-forming bacteria will predominate. "A concomitant accumulation of acidic intermediates of decomposition and a decrease in pH in the panning zone will occur. When the pH drops, the activity that produces methane will increase. , the bacteria continues to be reduced and causes a serious disruption of the process flow *

The attempt to solve the above-described disorder of the process in the known anaerobic Pauling zone generally involves the addition of large amounts of lime to the sludge digestion tank to enhance buffering and thereby increase the pH in the sludge digestion tank. By increasing the pH and by reducing the intake of

2 08 442 -

amount of sludge per unit time is sometimes the ability to return the sludge digester with the elimination of such a disorder back to normal operation. However, this correction is generally only suitable in the case of short-term fluctuations or process disturbances and usually not in the case of long-term fluctuations or interference conditions.

In the method according to the invention, the regulation and maintenance of the elevated working temperatures in the potting zone are achieved with minimal temperature variations, regardless of the climatic conditions, through the integration of a thermophilic or near-thermophilic aerobic panning treatment followed by anaerobic sludge treatment. In the process of the invention, the thermophilic or near thermophilic aerobic Digestion is generally able to provide more than enough heat to stabilize the anaerobic treatment on thermal Y / ege. This is due to the heat content of the partially stabilized sludge stream from the aerobic compaction zone to the anaerobic treatment. As a result, temperature variations in the anaerobic zone of the present process can be substantially eliminated, by altering such process parameters as, for example, the sludge retention time (duration) in the aerobic compaction zone, the sludge content of the sludge, the aerobic one Pauling zone is supplied, and the extent of heat exchange in the heating of the sludge entry before its introduction into the aerobic Paulungszone.

Another important advantage of the integrated method of the present invention beyond the usefulness attributable to the stability of the working temperature is the ability of such a system to compensate for a sporadic disturbance, such as overload, without sacrificing efficiency of the procedure

-yf-

- HQ-

to have to. Not only does the initial solubilization phase of the digestion process occur rapidly in a known anaerobic zone, but also the microbial activity of the facultative acid-forming bacteria occurs at high speed. After the occurrence of a sudden high solids loading in the known anaerobic Pauling system, solubilization and acidification occur At a faster rate than the methanogenic bacteria can use the acidic intermediates. As poles there is an accumulation of acidic components in the panning zone, a lowering of the pH in the panning zone, and a tendency to become soaked in sludge dewater contents. In the process of the present invention, the upstream thermophilic or near-thermophilic aerobic treatment promotes rapid dissolution of the biodegradable species in the sludge such that upon onset of overload in the aerobic compaction zone both rapid solubilization occurs in this aerobic compaction zone and stabilization of the This results in a compensation of the sudden overload and the subsequent influence on the downstream anaerobic Paulungszone is greatly reduced. Upon further treatment, the anaerobic pilling zone will receive a partially stabilized sludge in which the acidifying and methanogenic bacteria may grow in balance. "

Inasmuch as the aerobic coloring preferably makes use of a thermophilic panning zone in the present inventive sludge treatment process, the "process described and claimed in U.S. Patent No. 3,926,794 issued December 16, 1975 to M" .P. Vahldieck, incorporated herein by reference to the relevant scope, advantageously relates to the method of the present invention for treating a sewage

Haunter separation using the Biochemical Oxygen Demand (BOD) therefrom by the activated sludge process and to treat the resulting waste activated sludge according to the method of the invention.

Due to the history of the present invention, the activated sludge secondary treatment of the waste water is carried out in a known manner as follows. corresponding biochemical oxygen demand (BOD), for example urban wastewater, may first be subjected to treatment such as gross sands clearance and primary sedimentation to separate a primary sludge from wastewater consisting of biodegradable, suspended pesticides · This results in the formation of a pollutant-depleted primary effluent, which can then be fed to the secondary treatment system · In the secondary treatment, the primary effluent and the circulating sludge are mixed and mixed at a sufficient rate.

and aerated sufficiently long enough to arrive at a mixed liquid with a reduced level of biochemical oxygen demand. At the end of this, the mixed liquid is separated into the purified liquid and the activated sludge, and at least a major portion of the activated sludge is recycled, mixing with the primary waste water, and we obtain the above-mentioned circulating sludge. This wastewater treatment system may suitably be used in conjunction with the process of the present invention wherein the primary sludge and unreturned activated sludge are fed to the first potting zone according to the current process as sludge from that first zone.

As described in the above mentioned patent. , von Vahldieck uses oxygen gas for the thermophilic digestion of activated sludge in a warm closed digestion

- HH-

zone is used and the waste gas from the pumice zone finds at least a major part as a constituent of the vent gas in a cooler closed zone for activated sludge secondary treatment of the waste water. "According to the description of this patent, to get the high mass transfer driving force, which is necessary for the oxygen to effectively dissolve during aerobic digestion at elevated temperature, to use a relatively high purity oxygen gas as a vent gas for the Paulung treatment. At the elevated temperatures, the greater rate of biochemical degradation of the sludge produces in the aerobic Paulungszone significant amounts of carbon dioxide as a gaseous reaction product. Since the solubility of carbon dioxide is relatively low at the high temperatures characteristic of the aerobic thermophilic digestion, a significant amount of carbon dioxide in the aerobic sludge digestor enters the gas phase. Thereby, the effective concentration of oxygen in the aeration gas in the sludge digestion vessel becomes In addition, at high thermophilic temperatures, the oxygen concentration in the gas phase in the panning zone is further reduced by vapor pressure present in the vent gas due to the relatively high vapor pressure of the water at such temperature levels.

The foregoing influences reduce the driving force for the oxygen to mass transfer from the gas phase to the sludge in the thermophilic potting zone. The driving force for the oxygen mass transfer to the liquid sludge phase is also reduced as a result of the lower oxygen solubility at the elevated thermophilic temperature values. For these reasons, it can be seen from the Vahldieckschen patent that the oxygen-containing gas supplied to the wc thermophilic Paulungszone d, desirably an oxygen

2 08 442 ~ ^LiS ~ Berlin, d.8.3.1979

54 354/13

Concentration of at least 80 V! Ol · - ^ has. In the context of such a work restriction, the spent aeration gas from the thermophilic potting zone can be advantageously used as an oxidizing agent in an activated sludge secondary treatment system. Fig. 2 corresponds to a schematic flow diagram according to another embodiment of the present invention the statements of the Vahldieck patent can advantageously be used in conjunction with the practical conditions of use according to the invention.

How we now want to deal with Fig, 2 over the pipe 1Ot occurs' water, which has the biochemical oxygen demand, for example, dirty water, in the aeration zone 102 via the supply line 118 (dashed line) - first enters gas with an oxygen content of At least 40% by volume of oxygen enter the zone 102 and circulation activated sludge also passes into the zone 102 via the pipeline 108, which has a pump 109. Via the supply line 150, supernatant liquid is also supplied from the sludge thickener 151 to the closed aeration zone 102. In this figure, the pipelines for the transport of the liquids and the sludge are shown by solid lines, whereas the pipelines for the gases are indicated by dashed lines. For ease of illustration, the valves will not be reproduced, but the appropriate use of these valves in the practice of the present invention will be very well understood by those who are assured of the art. The streams mentioned above are intimately mixed in the aeration zone 102 by mechanical agitators 103. The agitators 103 may consist of centrifugal mixers or "SehneHruhrerη motorized, mounted in the Hähe the surface

208

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submerged in the liquid or below the surface. The oxygen gas can be introduced through the pipe 118 either above or below the liquid. Such an apparatus is not unknown to those well versed in the art and is to be selected to achieve a large area of contact between the flowing media with a minimum of work. When the oxygen gas bubbles into or diffuses into the liquid, the bubbles must be small, so that their total surface is large and their buoyancy is low. Dissolution of the oxygen is also assisted by immersing the gassing tubes in the liquid to a depth where the hydrostatic effect is significantly noticeable.

In preferred practical conditions of use, elements are suitably provided for continuous recirculation of the one flowing medium over the other flowing media in the aeration zone 102. For example, a compressor (not shown) may be connected to the headspace in the aeration zone by suitable conduits the aeration gas is due to the lower part of the zone where the release takes place in the form of small gas bubbles by means of a known explosive device. Alternatively, the stirring devices mentioned above can also be used for recirculation of the flowing media, as in the case of the surface aeration agitators. The aeration devices are generally rated for nominal performance by the so-called "standard air transfer efficiency". By this term, the performance of the device is characterized, oxygen -auslösung from the air in tap water containing dissolved oxygen equal to KuIl at a pressure of 1 atmosphere and a temperature of 20 ⁰ C to dissolve. Suitable devices are those which, via a standard air transfer

tion efficiency of at least 1.5 Ib O ₂ horsepower hour (PSh.) And preferably of at least 3.0. For these purposes, the power used for the design corresponds to the total usable energy consumed for both the stirring of the liquid and the gas / liquid contact.

The above-mentioned oxygen is introduced and comes into contact with the mixed liquid in an amount sufficient and at a corresponding rate to maintain the dissolved oxygen (DO) content in the mixed liquid at least 0.5 mg / l. Also, the temperature of the liquid is preferably maintained at least at 15 ^° C., so that equipment may be necessary in cold weather conditions to prevent a lower temperature in the aeration zone 102. For example, there are means for heating the incoming wastewater via the pipeline 101. The construction and operation of the wastewater treatment zone 102 may be as described in any of US Pat. Nos. 3,547,811, 3,547,812 or 3,547,815.

The oxygen-enriched mixed liquid is discharged from the closed aeration zone 102 and taken via the conduit 104 to the clarifier 105 for separation into the purified supernatant and activated sludge. Unconsumed oxygen-containing gas is discharged from the aeration zone 102 via the conduit 119 and may be discharged to the atmosphere, for example. This gas is discharged from the aeration zone at a rate regulated such that the oxygen content of this gas is not more than 40 % of the total oxygen content of the gas supplied to the closed aerobic digestion zone (discussed below).

2 08 442 .- - * -

However, let us now return to the clarification tank 105. The supernatant purified liquid is discharged via the piping 106 and the activated sludge is taken out through the piping 107. This sludge contains concentrated microorganisms in the total content of suspended solids (MLSS) in the concentration of about 10,000 to 40000 mg / l. The greater part of the activated sludge, for example at least 85 %, is returned to the aeration zone via conduit 108 and pump 109, preferably at a flow rate relative to the effluent having biochemical oxygen demand such that the volume ratio between the circulation sludge and the biochemical oxygen demand having effluent equal to 0 ^ 1: 0.5. The flow rates into the closed aeration zone 102 are preferably such that the total concentration of suspended solids (MLSS) therein is 4000 to 12000 mg / l and the volatile suspended solids content (MLVSS) is 3000 to 10000 mg / l , The contact time between the liquid and the solids with the aeration feed gas in the organic nutrient absorption / assimilation zone 102 is between 30 minutes and 24 hours. This time varies depending on the concentration of the waste water (content of biochemical oxygen demand), · the type of pollution, the content of solids during aeration and the temperature. These relationships are understandable to those versed in this field of technology.

The total sludge separated in the clarifier 105 is not returned to the aeration zone 102. There are two reasons for this. First, the activated sludge process produces a maximum yield of microorganisms, because the mass of new cells synthesized from the impurities in the wastewater is greater than the mass of cells that are produced during the treatment by autoxidation have arisen. Second, the wastewater does not normally contain any

- PS - :

2 08 442

biodegradable pesticides that settle and accumulate with the biomass. Therefore, a small fraction of the activated sludge must be removed to compensate for the total microorganism and nutrient supply (biochemical oxygen demand) and to suppress the accumulation of inert pesticides in the system. Sludge loss by discharge is typically less than 3 % of the total separated sludge amount and hardly more than 15 %. ,

While the waste sludge is a small fraction of the total solids separated in the clarifier, it is nonetheless often a large, absolute amount of material. Regardless of the amount produced, disposal of this sludge represents a significant part of the cost of wastewater treatment and, in addition, poses a serious ecological problem. The sludge is decayable and highly biologically active and often contains pathogenic bacteria. It is possible to suitably use the sludge as a fertilizer and / or landfill, but prior to such use sufficient stabilization of the sludge must be made to avoid health hazards and dangers. In addition, the high water content of the sludge (for example 96-98 %) must be reduced.

The waste sludge is taken from the sludge recirculation loop via the pipeline 111 to the clarifier 105, containing from 10000 to 40,000 mg / l of IdLSS (total suspended solids content). This is done initially about bei'derselben temperature as that of the .Abwassers in the aeration zone 102, for example at a temperature of 15 ⁰ C to 25 ⁰ C. The further transport is carried out at a Sindickungsbehälter 151 "The Eindickungsbehälter 151 causes a sludge concentration to a MLSS Salary between 20000

2 08 442 -so 60000 mg / l. Via the pipeline 152, the forwarding of the thickened sludge discharge to the sludge digestion system takes place.

In some cases, such as wastewater treatment in the presence of a high ambient temperature and at high concentrations of pesticide in the clarifier ent-s. The effluent sludge from the clarifier may not be necessary to thicken the waste sludge and the sludge in the pipe 111 may suitably bypass the tank 151 via the pipe 153 and subsequently enter the pipe 152 to be sent to the sludge digestion system. The overflow of the sinker (the supernatant liquid) is conveyed via piping I50 to the aeration zone 102, as already described above.

The thickened sludge in the conduit 152 may be heated, if necessary, before being introduced into the aerobic compaction zone 110. This purpose is served by the methane boiler 130. Alternatively, the sludge containing the stabilized sludge discharge from anaerobic anaerobic zone 120b could be subjected to a heat exchange process similar to that discussed above was described in more detail with the embodiment shown in Figure 1. The waste sludge is fed to a closed first expansion zone 110 either continuously or batchwise via the supply line 152. The aer.obe Paulungszone 110 is at a temperature in the range of 35 ⁰ C to 75 ⁰ C and preferably in the thermophilic range of 45 ⁰ 75 C.bis held .C .. A preferred range for the autothermal operation in the aerobic Paulungszone extends from 50 ⁰ C to 65 ⁰ G. the increased temperature in the closed first Paulungszone 110 can also be maintained in such a manner by an external heat energy is supplied.

2 08 442 -

This purpose is served, for example, by a suitably heated liquid located in a heat exchanger (not shown) located inside the potting zone. Because of the tendency of the pesticides to adhere and clog, the heat exchange surfaces located within the sludge dewatering container must not be branched or close together, but may be advantageously embedded in or attached to the container wall. ,

Via the pipeline 117, a second oxygen gas having an oxygen content of at least 80% by volume is fed to the closed first digestion zone 110. As will be described in more detail below, this gas has a sufficient amount to form part of the first oxygen gas that has been supplied to the aeration zone 102 via the conduit 118.

Preferably, the elevated temperature in the closed first digestion zone 110 is obtained by autothermal means, without requiring heat exchangers such as 130. The concentrated slurry that is characteristically in accordance with the oxygen aeration method of U.S. Patent ilr. 3547813 is very well suited for operation under autothermal conditions because of its reduced water content relative to its biodegradable "fuel" content. In addition, high solids concentrations reduce the size of a mud dump tank and therefore the heat conduction losses through the walls of the sludge digester are reduced. As previously stated, the total sludge solids content (IvILSS) in the digestion zone must be at least 20,000 make up mg / 1. Such considerations form the basis for this ». , ,

The upper limits for the solids concentrations in the aerobic Paul mud tank are generally given by two

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Factors Conditionally · Generally speaking, the maximum concentration depends on the ability of the known sedimentation and thickening apparatuses to reduce the water content. «Flotation apparatus, centrifugal separators and gravity thickeners often produce total suspended solids concentrations of the order of 60000 mg / l can be further increased by adding a primary sludge or concentrated waste from a source other than wastewater. The second factor limiting the concentration of solids is the increasing difficulty of dissolving oxygen in the digester and mixing the solids. A preferred upper limit is 80,000 mg / l, and most preferably 60,000 mg / l, to ensure that adequate oxygenation of the slurry can be carried out without undue energy expenditure for mixing the aeration gas with the slurry to operate.

The design of the digested sludge tank also has an effect on maintaining the elevated temperatures and concrete walls are preferred over metal walls because of the lower heat losses due to the thermal conductivity of the concrete walls. The heat losses can be further reduced by placing the containers underground and accumulating soil against any exposed vertical container walls. Thermal insulation by low density concrete or foam plastic may be applied over a metal lid, if necessary.

It is also preferable to practice the present invention in aerobic and anaerobic digester drums having a surface area to volume ratio of less than 0.8 ft ² / ft ³ (2.62 m ² / m ³ ). For this purpose, the term "surface" refers to the entire wall surface of the closed

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Digested sludges including the lid, the bottom and the side walls. Surface area / volume ratios greater than 0.8 result in large losses through heat conduction through the walls in relation to the amount of heat that must necessarily be maintained in the Paul mud tank. Such heat losses most likely necessitate the need for thermal insulation on the walls exposed to the ambient atmosphere.

The retention time (duration) of the sludge in the aerobic Paul mud tank also affects the elevated temperatures, in particular the autothermal temperatures that can be maintained. "It will be appreciated that numerous factors enter into the relationship between sludge residence time and temperature, such as for example, the buildability of the sludge and the sludge concentration (concentration of pesticides). Within the general field of use of the present invention, the sludge retention time in the first buffing zone ranges from 4 to 48 hours. Preferably, the sludge residence time (duration) in the first buffing zone is in the range of 12 to 30 hours and suitably in the range of 12 to 24 hours ».

The first Pauling zone 110 has mechanical stirrers 112 that may correspond to the same design used as stirrer 103 in the aeration zone 102, along with means for the continuous recirculation of one of the flowing media in the second gas and activated sludge stalls other 'streaming media in the Pauling Zone. ,

The second gas is at least 80 % oxygen and enters the closed aerobic zone of ash 110 where it is mixed with the sludge therein in an amount sufficient and at the rate of aerobic pumination of the sludge, while the total content of the sludge

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at least 20000 mg / l is maintained on suspended pesticides. '

Oxygen-depleted Pauling gas having a purity of at least 40% oxygen exits tubing 118 from closed Pauling zone 110 at a rate such that the oxygen content of this gas is at least 35 % of the oxygen content of oxygenate gas entering via tubing 117. The gas in conduit 118 is fed to the closed ventilation zone 102, at least as a main component of the above-mentioned first gas under satisfaction of the oxygen demand for biochemical enrichment of the waste water with oxygen, ^ hen necessary, using an external supplementary source for supplying the oxygen-containing gas be to increase AEEN oxygen-containing gas stream in der.Rohrleitung.

After the desired level of aerobic pumination treatment in the potting zone 110 is completed, the partially stabilized slurry from the first closed potting zone is discharged via the conduit 114 and fed to the part of the integrated anaerobic treatment system. In this embodiment, the second anaerobic compaction zone is composed of an acidification subzone 12Qa and a methane fermentation subzone 120b. The partially stabilized sludge in the tubing 114 is supplied from the first gum zone 110 to the acidification subzone 120a and held therein for a sludge retention time of 24 to 60 hours according to the slurry acidification requirements. The contents of the subzone 120a are continuously mixed by agitation means 121a to maintain a uniform rate of carbohydrate digestion, fats, and proteins to lower fatty acids in this subzone, upon completion of the necessary retention time (duration) in subzone 120a, the acidified sludge will be removed from this subsector via pipeline 126.

When the temperature of the sludge leaving sub-zone 120a is above that which is the optimum value for methane production, the temperature of the acidified sludge is desirably lowered to ensure a satisfactory puncture of methane-forming sub-zone 120b. As a result, the slurry passes through the conduit 126 in the heat exchanger 115 for heat exchange with a coolant passing through the heat exchanger through the conduit 160. The resulting, partially cooled, partially stabilized slurry exiting the heat exchanger 115 for discharge , Finally, flows through the pipe 127 in the sub-zone 120 b, in which the methane fermentation takes place. "The used for the heat exchange cooling medium in the conduit 160 may suitably consist of a cooling water flow, for example, this can be a part of the wastewater from the secondary clarifier over the line 106 or according to the above-described embodiment of the inflowing into the potting system mud entry.

The anaerobic Pauling subzone 120b consists of the methane-producing Pauling treatment of the process. In order to achieve an optimal puncture way, the sludge in the methane fermentation sub-zone 120b at a temperature of 35 ° C to 40 ⁰ C and preferably from 37 ⁰ C to 38 ⁰ C held The content of the sub-zone 120b is continuously agitating means, 12ib. This results in the formation of an extensive zone of effective degradation and a significant increase in the rate of stabilization reactions in this sub-zone. The mud retention time (duration) in the methane fermentation subzone 120b is preferably between 4 and 8 days, with the considerations discussed above governing the residence time of the mud in the anaerobic second pilling zone. The methane gas produced due to the xn of the sub-zone 120b biochemical reactions is from this sub-zone on the pipe

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leiturigi-128 removed, '- said Leitungein Mengenregelüiigsventil having 129 »A portion of this the lower zone 120b removed methane gas can be supplied via the pipe 132 to the boiler 130, while the remaining part of the methane gas through the pipe 131 is removed from the process, in order to be supplied for further treatment and / or for other <end-uses. The still-stabilized slurry having not more than 40% of the initial content of the inflowing sludge of biodegradable volatile suspended solids, and preferably not more than 20 % thereof, is discharged from the process via the pipeline 133.

Fig. 3 corresponds to a schematic flow diagram of another embodiment of the invention wherein sludge from the primary and secondary effluent treatment sites is fed to the sludge digestion system. This embodiment illustrates a process sequence within the scope of the present invention wherein a thermophilic aerobic first digestion zone having a thermophilic anaerobic second digestion zone So far, thermophilic anaerobic digestion has not been widely used in commercial practice. The reason for such a limited use is that the problems in the known mesophilic anaerobic operation, namely the thermal instability present and the extraordinary sensitivity to changes in the process conditions, which have already been discussed above, in the thermophilic anaerobic digestion in an even more critical extent. It is indeed the case that, because of the uneven stability of the thermophilic anaerobic digestion process, this sludge treatment process is still poorly used in commercial sludge digestion applications.

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been given attention. These problems of instability of operation and disproportionate sensitivity to process variations are overcome in the thermophilic aerobic / anaerobic embodiment of the present invention in the same manner as described above in connection with the embodiments of the present invention using an anaerobic mesophilic second digestion step.

In Fig. 3, the raw sewage, which is composed, for example, from urban waste water from industrial waste waters and from Regenwaoser flows through the pipe 24O of the primary sedimentation zone 24I to _e This sedimentation zone 241 can appropriately consist of a Schwerkraftklärbehälter a known type, well known in the art * In the sedimentation zone, the incoming effluent is transferred to a primary effluent having a reduced biochemical oxygen demand, which is supplied via piping 201 to aeration zone 202, and to a sludge tower consisting of settled sludge, separated from the sedimentation zone 24I via, the pipe 242 is removed. Oxygen-containing aeration gas likewise enters the aeration zone 202 via the pipeline 218, the supernatant liquid from the sludge thickener passes via the pipeline 250 into the aeration zone 202, and the activated sludge is returned via the pipeline 208. In the aeration zone 202 are devices 203 for the mixing and the recirculation of the flowing media. This causes a mixing of the various flowing media that has been fed to the aeration3zone. A mixed liquid is formed and at the same time there is a continuous recirculation of a component of the mixed liquids and

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of the oxygen-containing aeration gas compared to the other flowing media present in this treatment zone. As already discussed above, the advantages provided for mixing and recirculating the flowing media. , ,

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directions suitably consist of a Tauchgasdurchblaseinrichtung in combination with a Tauchrührerlaufrad or from a surface aeration stirrer. For example, after the required aeration time of, for example, 2 to 6 hours, a mixed fluid having a depleted biochemical oxygen demand and an oxygen-depleted aeration gas containing at least 21% by weight of oxygen from the aeration zone -202 will be discharged via the lines 204 and 219, respectively ,

The oxygen-enriched, mixed liquid having a depleted biochemical oxygen demand passes via the pipeline 204 into the secondary sedimentation zone 205, in which activated sludge is separated from the purified liquid. The purified liquid passes out of the process for discharge via the pipeline 206. The settled activated sludge is taken from the secondary sedimentation zone 203 via the pipeline 207. A larger amount of this withdrawn sludge is recycled as circulating sludge via the pipeline 208 by means of the circulation pump 209 of the aeration zone 202. The remainder of the non-recirculated sludge, which may constitute between 3 % and 10% of the sludge in the pipeline 207, passes via the pipeline 252 into the sludge ind. 251>

In the sludge thickener 251 is another sludge settling thickening zone in which the sludge is concentrated to solids values between 2% and β % , ie, it is MLSS values between 20000 and 60000 mg / l. The thickened mud effluent is passed via the conduit 245 and intertwined with primary mud via the conduit 242 from the primary sedimentation zone 241 resulting in the combined mud stream via the conduit 211. " The supernatant liquid from the sludge thickener 251 is supplied via the pipeline 250 to the aeration zone 202, as has already been described above.

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The combined slurry stream via the pipe 211 may be partially heated, if desired, by indirect heat exchange with the warm stabilized slurry discharged from the second digestion zone 220, as further described below. Subsequently, this slurry enters the first . Pauling Zone 210 via Pipeline 248. Prior to introduction to the first Pauling Zone 210, the sludge in the pipeline 248 may be further heated by the methane gas heated heater 231, which receives the methane gas for combustion via the pipeline 227.

If the ambient temperature conditions are sufficient to eliminate the need to heat the incoming sludge into the potting system, the sludge may be circulated around the heat exchanger 244 and the heater 231, to which the bypass pipes 261 and 263, respectively, are provided.

In the closed first Pauling zone 210, the thermophilic aerobic treatment of the incoming waste sludge is carried out. Via the pipeline 217, the pollen zone 210 is supplied with aeration gas having an oxygen content of at least 50% by volume and preferably with an oxygen content of at least 80% by volume. Mechanical stirrers 212 simultaneously mix and continuously recirculate the incoming sludge mixture over the oxygen-containing gas. The supply rate of the aeration gas and the energy intake of the mechanical agitators 212 are such that oxygen in the sludge in the first composting zone 210 is dissolved in sufficient quantity and velocity to meet the respiration requirements of the sludge during the aerobic treatment in the first zone of Pauling 210.

The mud remains in the first Paulingzone 210 at a.

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thermophllen temperature of 45 ⁰ C to 75 ° C for 4 to 48 hours to degradable to a partial reduction in the content of the sludge of biologically to reach flüchtigenj suspended Peststoffen. The partially stabilized slurry is discharged from the aerobic digestion zone 210 via the conduit 216 and the oxygen-depleted Pauling gas is separately discharged therefrom from the digestion zone 210 via the conduit 218.

Via the supply line 216, the partially stabilized sludge from the first composting zone passes into the closed second compaction zone 220.

The second potting zone 220 consists of a thermophilic anaerobic pumice slurry. "In order to achieve optimum performance, the sludge in this potting zone becomes one. Temperature in the anaerobic thermophilic temperature range between 40 ⁰ C and 60 ⁰ C, and preferably maintained between 45 ⁰ C and 50 C. As a result of the thermophilic treatment in both the first and in the second Paulungszone can in this embodiment of the present invention, the partially stabilized sludge the first zone of Pauling be supplied directly to the second zone of the Pauling, as the reproduction can be removed without a heating or cooling heat exchange between the zones, provided that the thermophilic temperatures in the respective Paulungszonen are sufficiently close to each other. Alternatively, it may be desirable in some cases, the second. To operate Paulungzone at sufficiently higher or lower temperatures relative to the first aerobic Paulungszone so that heating or cooling of the partially stabilized sludge after the aerobic Paulung between the Paulungszonen is favorable. The heating can be done by means of a heater with methane gas heating similar to the heater 231; The cooling may be accomplished by heat exchange of the partially stabilized sludge from the first bomber zone with the incoming one

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Be carried out sludge which is supplied to the Paulungssystem as further -ή above in connection with the inventive embodiments according to the illustrations in FIGS. And described 2 * Since it is critical even during the thermophilic anaerobic Paulung than in the mesophilic anaerobic Paulung, In addition, to ensure that there are no temperature variations in the Pauling Zone, it may additionally be desirable to use a well-insulated container as a sludge treatment tank for thermophilic anaerobic treatment. As a result, there is a corresponding security against serious climatic fluctuations.

In the second panning zone 220, the slurry is continuously mixed by mechanical agitators 221 to maintain a high rate of stabilization. Methane gas, which is produced as a poling of the biochemical reactions occurring during anaerobic annealing, is drained from the second maceration zone via the conduit 223. This methane gas can be mixed with oxygen-containing gas, such as with air or with the acid-depleted Pauling gas from the aerobic Pauling zone, and burned as a heating gas to provide heat so that the sludge can be maintained at an elevated temperature in a panning zone or in both potting zones ,

In the present process, according to playback a · part of the methane gas via conduits 223 and 227 supplied to the methane gas boiler 231 where it is burnt in order the heat for maintaining the sludge in the first Paulungszone on the thermophilic temperature of 45 ⁰ C to 75 ⁰ C to deliver. The remaining methane gas is withdrawn and removed from the panning system via pipe 228. The still stabilized sludge from the anaerobic scrubber zone containing no more than 40 % of the content of the biodegradable, volatile, suspended sludge sludge fed to the potting system via tubing 248 and

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preferably not more than 20 % thereof is discharged from the second digestion zone via the drill pipe 225. This sludge discharge then passes through the heat exchanger 244 for heat recovery from the discharged sludge, Finally, the sludge thus treated passes through the pipe 243 for discharge from the treatment system ·

The nature of the biological activity in the aerobic fouling zone in the embodiment according to the invention just described according to FIG. 3 differs significantly from the biological activity in the aerobic growth zone of the embodiment of the invention described above according to FIG of different mud sources · In the embodiment according to Pig. 2 is in the slurry that is supplied to the Faulungssystem as inflowing feedstock _s whereas the inflowing sludge primary exclusively activated sludge from the secondary the sanitation Eerbehandlungssystemj in embodying acc Fig. 3, both of the secondary sludge to the activated sludge treatment, as well as from the Mud of raw sewage sedimentation treatment is composed. Since the organic material of the secondary sludge consists mainly of viable microorganisms, the aerobic digestion of this sludge consists of the various biochemical reaction stages of cell dissolution, the assimilation of the dissolution products to the synthesis of new, viable material and the At-. On the other hand, the primary sludge consists mainly of a non-viable organic material which can be used by the microorganisms in the sludge as the nutrient. Thus, during the aerobic digestion of a primary sludge, the microbial population of the sludge undergoes an essential phase

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As a result, the aerobic digestion of the primary sludge takes place to a greater extent both in terms of synthesis and cellular respiration than in the aerobic digestion of the secondary sludge Case is. In addition, the aerobic digestion of the primary sludge leads to a lower overall reduction of the biodegradable, volatile solids than is the case with the aerobic digestion of the secondary sludge, based on a comparable sludge retention time (duration) for digestion. The overall reduction The sludge content of biodegradable volatile solids during digestion represents a difference in competing digestion processes of cell synthesis and cellular respiration.

Cellular respiration during sludge digestion is exothermic, and for the reasons discussed above, the primary sludge has a higher heat dissipation capacity per volume weight of biodegradable, volatile, suspended solids removed during digestion than at the secondary chain is therefore the case. Consequently, a smaller total reduction of the volatile, suspended. Solids required to reach and maintain a given temperature during the aerobic digestion of the primary sludge, as is the case with the secondary sludge. Thus, the embodiment of the present invention, as shown in Fig. 3, wherein the sludge fed to the digestion system is composed of both the primary sludge and the secondary sludge * at a given temperature with a lesser reduction in the sludge content volatile, suspended solids

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in the aerobic digestion zone, as is the case for the aerobic Pauling zone in the embodiment of Figure 2, using only secondary sludge. · A lesser reduction in the sludge content of biodegradable, volatile, suspended particulate matter in the aerobic maceration zone of the potting system, however, requires that the sludge retention time (duration) in the anaerobic compaction zone be increased correspondingly to arrive at a given overall level of volatile volatilized particulate removal. Since a larger part of the total · ?; Thus, in the event of volatile suspended solids being produced in the anaerobic digestion zone, "the system may produce larger amounts of methane gas in the treatment of the primary sludge in the anaerobic digestion zone, as compared with the Pauluag system in which Thus, according to Pig, 3, the embodiment of the present invention is capable, by its nature, of delivering greater quantities of methane gas than is the case with the system of Figure 2, but at the expense of a greater sludge retention time (duration). in the anaerobic digestion zone in the first-mentioned case, '.

With respect to the preceding discussion, the performance for heating the sludge entering the potting system prior to the introduction of the sludge into the aerobic digestion zone is provided in each of the illustrative embodiments of the present invention described above. In a given application, such heating may occur necessary or not · There is a dependency on various factors, such as the content of the sludge of solids, the ambient temperature, the sludge retention time (duration)

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In the aerobic digestion zone and the type and composition of the sludge encountered. 4 corresponds to a graph of the temperature of the sludge flowing into the first closed Pauling zone as a puncture of the total content of sludge of suspended solids (MLSS) flowing into the first closed digestion zone. These temperature values are necessary to autothermally maintain a working temperature of 50 ^° C. in the first digestion zone during a sludge retention time (duration) of 24 hours. This graph represents a biological secondary sludge having a volatile suspended solids content ratio of 0.79 total solids suspended solids (VSS / TSS) and having a biological volumetric content of IOOOOO BTU / lb at remote volatiles. suspended pesticides.

The graph of Fig. 4 shows that the thermophilic operation can be achieved without having to heat the sludge flowing into the digestion system before the introduction of the sludge into the aerobic Paulungszone occurs when the incoming sludge over a sufficient concentration Has pesticides. For example, if a slurry having a total concentration of Peststoffen unlock is 3%, the temperature of the zageführten thermophilic aerobic sludge Paulungszone must only about 16 ⁰ C make up to maintain autothermal operation.

All of the embodiments of the present invention described above are capable of providing a fully pasteurized sludge product, since in each of these instances all of the sludge entering the digestion system passes through an aerobic compaction zone in which high sludge flows

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54

Temperatures of the order of at least 50 ° C to 52 ⁰ C used v / to earth ground in order to achieve full Schlammpasteurisierung. However, there may be applications where the end use of the sludge does not require a fully pasteurized product or where the sludge itself does not require pasteurization because of the absence of any appreciable concentration of pathogenic organisms therein. FIG. 5 corresponds to a schematic flow diagram of another embodiment of the invention Within the broad scope of the present invention, a minor portion of the sludge flowing into the digestion sys- tem is fed to the second faucet zone. This method is suitable for the above mentioned sludge digestion applications where complete pasteurization of the sludge is not required. In the reproduced in Fig. 5 embodiment, a greater part of the inflow into the digestion system via the feed line 311 sludge of the closed first digestion zone 310 via the supply line 331 is given before the introduction of the sludge in the first digestion zone 310 this on the way the supply line 331 may be heated, if desired, using the methane gas fired boiler 330.

Oxygen-containing aeration gas having an oxygen content of at least 50% by volume and preferably at least 80% by volume of the aerobic digestion zone 310 is introduced via the conduit 317. The sludge flowing into this digestion zone is suitably mixed by the agitators 312 and continuously recirculated against the oxygen-containing aeration gas in this zone. The mixing of the sludge and the aeration gas takes place in sufficient quantity and speed for the

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aerobic sludge digestion in the Pauling zone 310. The sludge is maintained in the aerobic Paulungszone at the thermophilic temperature between 45 ° C and 75 ° C for 4 to 48 hours. Via the pipe 318, the oxygen-depleted Paulungsgas from the first Paulingzone for discharge and via the pipe 316, the sludge with a partially depleted content of biodegradable, suspended suspended pests from the Paulungszone separately discharged.

The partially stabilized slurry is then supplied via the conduit 316 to the closed second potting zone 320 in which mesophilic temperature conditions exist. Since the temperature of the discharged from the first Paulungszone sludge between 45 ⁰ G and 75 ⁰ C, the temperature of this slurry is lowered in a suitable manner prior to introduction into the second Paulungszone, so that the preferred mesophilic temperature conditions for the mesophilic anaerobic digestion in the second zone of Pauling can be maintained. In the illustration of Figure 1, the minor portion of the mud entering the potting system bypasses the methane gas kettle 330 and the aerobic pumble zone 310 via the pipe 329 and direct mixing with the warm mud via the pipe 316. The flow rate of the incoming slush slurry stream is adjusted in such a way that the. Temperature of the combined sludge stream, which is supplied to the anaerobic Paulungszone 320, sufficient to maintain a working temperature in the Paulungszone 320 between 35 ° C and 40 ⁰ C.

In the second Pauling zone, the sludge is mixed by recirculation of the methane gas over the sludge in this zone of the sludge to increase the stabilization rate.

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in the second digestion zone to effectively maintain high levels. Via the pipeline 323, methane gas, which is generated as a result of the biochemical reactions in the second digestion zone 320, is discharged from this zone. Via a branch, the supply of this gas into the flow circuit 340 with a compressor 326 and the resulting compressed methane gas is the. Mud is supplied in the second zone, for example using blowing devices (not shown). This then causes mixing of the sludge and recirculation. From pipe 323, part of the methane gas may be supplied via pipe 327 to the methane-heated boiler 330 and the remainder of the gas passes via pipe 328 from the digestion system for discharge. The still stabilized sludge, which is less than 40 % of the original existing content of the sludge flowing into the digestion system via the supply line 331 of biodegradable, volatile, suspended solids is discharged from the second digestion zone via the pipe 325 for further treatment (for example, for drainage) and / or final disposal.

The advantages of the present invention are further illustrated by the following examples:

Example 1

This example compares the performance of the present invention when practiced according to the embodiment of Fig. 2 with a known anaerobic system having a high throughput. The further description is based on the treatment of a waste sludge from a wastewater treatment plant with a capacity of 10 χ 10 gallons per day (MGD). The . schematic flow diagram in Fig.2

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serves as reference basis ·

About the drill line 111 is a combined, consisting of 50 % of primary sludge and 50 % of secondary sludge entry material with a starting temperature of 18 ° C the Pauling system according to Pig. 2 supplied. The sludge is blended with a total suspended matter content of 39400 mg / l and a ratio of volatile, suspended pesticides to the total suspended solids content of. 12% fed to the system at a flow rate of 0.09 MGD. To the mud in the aero. ben Paulungszone maintain at an operating temperature of 50 ⁰ 110 C for 24 hours, the inflowing sludge using the methane gas boiler 130 to about 23 ⁰ C is erwärmtβ on the basis of a conversion efficiency of the heating value of the methane gas in Färme be about 25,000 ft ^ methane gas per day, generated in the anaerobic Paulungszone, needed to supply the boiler 130 with heating gas.

In the aerobic Pauling Zone, there is an approximately 8% reduction in the volatile suspended solids content

2 08 442 -μ-

(content of biodegradable, volatile suspended solids equal to 16%, content of biodegradable, volatile, suspended substances corresponds to approximately 50% of the total volatile volatile substance content), so that a partially digested sludge with volatile content "This sub-zone operates at the" thermophilic temperature, maintaining a 24-hour sludge retention time (duration). "At this stage of treatment, there is a 10% reduction in the level of incoming sludge Via the pipeline 126, a sludge containing 23500 mg / l volatile suspended solids is then discharged to the methane fermentation subzone 120b for discharge. In the heat recovery device 115, enough heat is extracted from the discharged sludge to carry out an operation temperature in the methane fermentation subzone 120b of 38 ⁰ C.

The sludge dwell time (duration) in the methane fermentation subzone 120b is 5 days *. There is an overall reduction in the sludge content of volatile suspended solids of .40 % for the integrated system (reduction in sludge biodegradable volatiles content) , suspended pesticides of 80 %). The methane fermentation subzone generates about 73,000 fο of methane gas per day, which equates to a total calorific value of 43 x 10 BTU per day. Since 25,000 ft-1 methane gas per day is needed to operate the methane gas boiler 130, 48,000 ft of methane gas per day with a total calorific value of 29 x 10 BTU per day is available to be routed from the sludge digestion system.

When the combined sludge with the flow rate of 0.09 MGD on which the. above description is instead fed to a known anaerobic sludge digester

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For example, with high throughput, a mud retention time (duration) of about 13 days would be necessary to achieve the same reduction in the level of volatile sludge sludge. Although 128,000 ft 3 of methane gas per day, corresponding to about 77 x 10 BTU per day, are produced in the known high throughput anaerobic sludge digester, about 60 x 10 x BTU per day of heat is required, with a 50% conversion of the Heat value in heat to maintain optimum working temperature conditions in the sludge dewatering vessel at high throughput. Thus, the known system requires 86 % greater capacity than the above-described embodiment of the present invention, assuming the retention time (duration) requirements. There are about 40 % less methane gas available for on-line use under normal working conditions.

Example 2

This example describes a specific operation of the present invention according to the embodiment in Figure 5. The incoming sludge entry has a flow rate of 0.06 MGD. The entry is composed of a combined sludge with 50 % primary sludge and 50 % secondary sludge from a wastewater treatment plant. The sludge stream flowing in via the feed line 311, which has a temperature of 20 ° C. and a total suspended solids content of 4 % (VSS / TSS = 0.75), is subdivided. In this case, a portion of the sludge with a flow rate of 0.046 MGD over die.Zuleitung 331 directly fed to the thermophilic aerobic digestion zone and another part of the sludge with a flow rate of 0.014 MGD as a bypass flow über.die pipe 329 out. Insofar as the temperature and concentration of the sludge on suspended solids

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In this case, there is no need to heat the sludge prior to introduction into the aerobic compaction zone, in this case there is no need to heat the sludge prior to introduction into the aerobic compaction zone. The retention time (lurking) in the first pilling zone 310 is about 24 hours and, as described, the thermophilic temperatures in this first pilling zone are achieved on autothermal Y / ege Via the drilling line 31έ, a pasteurized sludge with a temperature of 5 ° .GEG The aerobic Paulungszone for discharge "Then there is a mixing with the cold mud bypass stream via the pipe 329 instead. This combined mudstream then enters the anaerobic zone 320 in which the sludge remains in the absence of oxygen for approximately 8 days. * This results in an approximately 40% reduction in the total volatile substance content (80% reduction in the Sludge on biodegradable, volatile, suspended pesticides) _c The anaerobic digestion zone produces methane gas at a velocity of approximately 72,000 ft per day. This equates to about 40 χ 10 BTUs per day. All the methane gas produced is available for onward transmission from this treatment system,

If the combined inflow sludge entry at the 0.06 MGD flow rate instead would be supplied to a known anaerobic Paul mud tank characterized by high throughput, a sludge retention time (duration) of about 15 days would be required to achieve the same reduction in content the sludge of volatile substances. Although 90,000 ft.sup.- ³ methane gas per day is equivalent to about 50.times.10.sup.-4 BTU per day by the known anaerobic sludge digestion tank

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approximately 45 x 10 BTU per day are needed, and this is done with a 50% conversion of calorific value to the farms to maintain optimal anaerobic working temperature conditions in the high throughput sludge digestion vessel. Thus, in this case, a known anaerobic digestion system requires approximately 65 % longer sludge retention time (duration), but only produces a total gaseous energy equivalent to 5 x 10 BTU per day, compared to the 40 x 10 BTU per day in the combined System · Consequently, after the use of the methane gas generated in the interior as the heat source, the known system has substantially less methane gas for the forwarding than is the case with the method according to the present invention.

Example 3 · "

This example compares the performance of the present invention to an embodiment of the embodiment of FIG. 1 with a known anaerobic system characterized by a high throughput.

A secondary sludge from an oxygen receiving the sanitation 8erbehandlungssystem with an initial temperature of 15 ⁰ C is first in the heat exchanger 22 by Y / ärmeaustausch with the effluent from the anaerobic Faulachlammbehälter and then in the heat exchanger 15 aerobic by heat exchange with the effluent from the thermophilic The first heat exchange in the heat exchanger 22 increases the temperature of the incoming sludge from 15 ° C to about 25 ⁰ C, whereas the temperature of the stabilized sludge discharge from the anaerobic digestion A 20 is lowered from about 35 ^P C to 25 ° C. The second heat exchange in the heat exchanger 15 increases the temperature of the incoming sludge to about 30 ° C, where against the temperature of the Schiammaustrages from the aerobic

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Faulungszone 10 is reduced from about 50 ⁰ C to 45 ° C. The incoming sludge has a total solids content (MLSS) of 34400 mg / l and is represented by a ratio of the content of the

2 08 442 - * -

Mud of volatile, suspended solids to the total sludge content of 78 % suspended solids. This slurry is fed to the first Pauling zone at a flow rate of 0.06 MGD. In the first aerobic zone, a working temperature of 50 ° G is maintained with a sludge retention time (duration) of 24 hours.

In the aerobic potting zone, an approximately I6% reduction in the sludge content of volatile, suspended pesticides (32 % reduction in biodegradable, suspended pesticidal sludge content of the sludge ) is achieved so that a partially stabilized sludge containing Slurry of volatile suspended solids of 22500 mg / l after heat exchange with the incoming sludge in the heat exchanger 15 is supplied via the conduit 16 to the anaerobic compaction zone 20.

The anaerobic maceration zone works with a residence time (duration) of the sludge of 8 days. This results in a total reduction of the sludge content of volatile suspended solids of 42 % (reduction of biodegradability of biodegradable, suspended solids sludge to 84 %) for the integrated system. Anaerobic Pauling Zone 20 provides approximately 51800 ft-1 methane gas per day, which corresponds to a total calorific value of approximately 28 x 10 BTU per day. All methane gas is available for onward transmission from the Pauling system.

Instead, if the slurry entering the potting system at the flow rate of 0.06 MGD, as described above, would be a known one. At least one Schlain retention time (duration) of 14 days would be necessary to deliver the same reduction in the sludge content of volatile, suspended pesticide to high-throughput anaerobic Paul mud reservoirs.

208 442 - ^ -

to achieve substances. Although 846,000 ft-1 methane gas per day is produced in such a known high throughput system, corresponding to about 47 x 10 BTU per day, about 45 x 10 BTU per day is needed to maintain optimum operating temperature conditions in the high throughput sludge digestion tank. It is assumed that a conversion of the calorific value into heat of 50 % · The known anaerobic treatment system therefore requires about 55 % higher fitting capacity (container holding capacity) and has about 26 χ 10 BTU of methane gas per day weiterzubefordern less than that for the corresponding above described system of the present invention applies.

Although the preferred embodiments have been described in detail, it will be understood that other embodiments can be envisioned with corresponding modifications to the described features and characteristics which are within the scope of the present invention. For example, according to the present method, the aerobic bagging operation may be carried out in series treatment tanks or in a subdivided tank, with the single component row tanks or individual volumes in the subdivided basin functioning as subzones of the aerobic zone. In such a manner, the aerobic potting zone may be placed in the mold of a sludge digging room having multiple chambers for stepwise, parallel flow sludge and aeration gases. Such a configuration of an aerobic zone is well known to those skilled in the art. A description of such a configuration can be found, for example, in U.S. Patent No. 3,926,794, issued to I.P. Vahldieck. ,

Claims (18)

2 08 442 Erfindungsansprach Sludge digestion under aerobic / anaerobic conditions, characterized by the following steps: a) introduction of the sludge and the aeration feed gas, consisting of at least 20% oxygen, into a first composting zone and mixing the constituents in this first digestion zone in sufficient quantity and velocity for the aerobic digestion of the sludge, during , the total suspended solids content (MLSS) of the slurry is maintained at least on the order of 20,000 mg / l and the temperature of the slurry is maintained in the range of 35 ° C to 75 ° C in the first digestion zone b) Continuing aerobic digestion according to step a) during a sludge retention time (duration) of 4 to 48 hours for the purpose of partially reducing the biodegradable, volatile suspended solids content of the sludge fed to the first digestion zone and discharging the sludge partially stabilized sludge from the first digestion zone; c) Anaerobic digestion of the partially stabilized sludge discharged from the first digestion zone in a closed second digestion zone while maintaining the temperature of the sludge in this second digestion zone in the range of 25 ^° C. to 60 ^° C. while maintaining a sufficient solid retention time (duration) to achieve a further reduction in the biodegradable, suspended volumetric solids content of the sludge to less than about 40 % of the biodegradable, suspended, volatilised solids content of the sludge fed to the first digestion zone in step a); and thereby to form methane gas and 2 08 442 -? 3- Berlin, 16.7 · 1979 54 354/13 d) discharging the still stabilized sludge and the methane gas from the second zone ₀ 2. Sludge digestion method according to item 1, characterized by the following steps: a) introduction of the ScEammes and the vent feed gas consisting of at least 20 by volume ₀ -% oxygen, 'in a first Paulungszone and mixture of the ingredients in this first Paulungszone in sufficient quantity and velocity to satisfy the aerobic Paulungsatmungsanforderungen of the slurry, and maintaining the total content of suspended matter (MLSS) of the sludge in the first zone of at least the order of 20,000 mg / l; b) maintaining the slurry 'in the first Paulungszone during step a) at a temperature in the range of from 35 · ⁰ C to 75 ⁰ C; c) plugging step b) during a sludge retention time (duration) of 4 to 48 hours for the purpose of partially reducing the biodegradable, volatile, suspended particulate matter content of the sludge supplied to the first composting zone; ' d) discharging the partially stabilized sludge from the first zone of incineration; e) introducing the partially stabilized sludge from step d) into a closed second panning zone; and ο. «ου" Uj /^*c>{)^.i<i _w 2 08 442 -so- 16.7.1979 54 354/13 f) maintaining the sludge in the second Faulungszone under anaerobic conditions at a temperature of 25 ⁰ C to 6O ⁰ C (for a sufficient Peststoffretentionszeit duration) degradable, for the purpose of further reducing the content of organic, volatile suspended solids of the slurry to less than about 40% of the biodegradable, volatile, suspended solids content of the sludge fed to the first digestion zone in step a), and formation of methane gas as well as discharge of the still stabilized sludge and methane gas from the second digestion zone 3 · Sludge digestion according to point 1, characterized by the following steps: a) introduction of the sludge and the aeration feed gas, consisting of at least 20 vol .-% oxygen, in a first digestion zone and mixing the components in this first digestion zone in sufficient quantity and speed, to a utilization of at least 0.03 lbs oxygen per Ib of to obtain volatile suspended solids (VSS) in the sludge fed to the first digestion zone while maintaining the total suspended solids content (MLSS) of the sludge in the first digestion zone of the order of at least 20000 mg / 1; b) maintaining the sludge in the first digestion zone during step a) at a temperature in the range of 35 ⁰ C to 75 ° C; c) Continuation of stage b) during a sludge regeneration 2 Α © Ά MO - ^gA ~ Berlin, d.8.3.1979 ^{08 442} 54 354/13 4 to 48 hours for the purpose of partially reducing the content of biodegradable, volatile, suspended solids of the sludge fed to the first digestion zone; d) discharging the partially stabilized sludge from the first digestion zone; β) introducing the partially stabilized sludge from step d) into a closed second digestion zone; and f.) upright degradable conservation of the sludge in the second Faulungszone under anaerobic conditions at a temperature of 25 ° C to 6O ⁰ C (for a sufficient Festatoffretentionszeit duration) for the purpose of further reducing the content of organic, volatile suspended solids of the sludge to less than about 40 % of the biodegradable, volatile, suspended solids content of the sludge fed to the first digestion zone in step a), thereby producing methane gas and discharging the further stabilized sludge and methane gas from the second digestion zone. 4. A process according to any one of items 1, 2 or 3, characterized in that the oxygen-containing aeration feed gas and the sludge in the first digestion zone are mixed in sufficient quantity and velocity to produce from 0.10 to 0.35 lbs of oxygen per each Ib of the volatile suspended solids (VSS) in the sludge, that of the first digestion zone 2 08 442 - «* - Berliri, d.8.3.1979 54 '354/13 was supplied, ζα arrive · Method according to one of the items 1, 2 or 3, characterized in that the content of volatile suspended pesticides of the sludge supplied to the first potting zone in the first rearing zone is reduced by 5 to 20 % . 6. Method according to one of the items 1, 2 or 3 »characterized in that the first potting zone is provided with a cover plate in order to allow a gas space over the surface of the sludge. and that the aeration feed gas contains at least 50 Vo1 · - $ oxygen · The method according to item 6, characterized in that a circulation of one part of the aeration gas and the mud liquid against the other flowing medium in the first Pauling zone and a discharge of the oxygen-depleted Paulungsgases with at least 21 vol .-% oxygen from the first Paulingzone independently Discharge of the partially stabilized sludge takes place · Method according to one of the items 1, 2 or 3, characterized in that the sludge fed to the first composting zone has a total suspended solids content of the order of 20,000 to 80,000 mg / l. 3 _% process according to any one of items 1, 2 or 3, characterized in that the sludge retention time (duration) of the sludge in the first composting zone is 12 to 30 hours, 10, method according to one of the items 1, 2 or 3, characterized 442 ~ * ³ ~ Berlin, d.8.3.1979 54 354/13 characterized in that the sludge is heated prior to introduction into the first composting zone in order to maintain the temperature in the first compaction zone.
rechtsuerhalten. temperature in the first digestion zone to 35 ° C to 75 ° C 11. The method according to any one of 1, 2 or 3, characterized in that the · temperature of the slurry is maintained in the second Paulungszone in the range from 35 ° C to 4O ⁰ G for the purpose of mesophilic sludge in the second Paulungszone · 12, A method according to any one of 1, 2 or 3, characterized in that the temperature of the sludge in the second Faulungszone in the range of 45 ⁰ C to 50 ⁰ G wirdo maintained for the purpose of thermophilic sludge digestion in the second Paulungszone The method according to any one of items 1, 2 or 3 »characterized in that the sludge retention time in the second panning zone is sufficient to further reduce the content of biodegradable, volatile, suspended pesticides of the _; Sludge to reach less than about 20 % of the biodegradable, volatile, suspended sludge content of the sludge fed to the first pilling zone in step a); 14 »Method according to one of the items 1, 2 or 3, characterized in that the sludge retention time in the second pilling zone extends to 4 to 12 days. 15 "Method according to one of the items 1, 2 or 3", characterized in that each of the first and second zones of compaction has a surface / volume ratio. 2 08 442 - «- Berlih, d, 8.3.1979 54 354/13 ner than 0.8 ft ² / ft ^ 16, method according to any one of items 1, 2 or 3 _f, characterized in that the sludge in the second composting zone is mixed by circulating the methane gas within the sludge in this digestion zone. Method according to any one of items 1, 2 or 3, characterized in that the aeration feed gas is heated prior to introduction into the first buffing zone to allow the tempering therein;
rechtzuerhalten · therein the temperature in the range of 35 ⁰ C to 75 ⁰ C on Method according to one of the items 1, 2 or 3, characterized in that, prior to introduction into the first potting zone, the sludge is heated by indirect heat exchange with the still stabilized sludge discharged from the second pilling zone. 19 * A process according to item 18, characterized in that the temperature of the sludge is maintained in the second Paulungszone in the range from 35 ° C to 40 ⁰ C and the heated sludge further before introduction into the first Paulungszone by indirect heat exchange with the partially stabilized sludge, which is discharged from the first Paulingzone, is heated. Method according to one of the items 1, 2 or 3, characterized in that the second panning zone is composed of an acidification subzone and a methane fermentation subzone, wherein the partially stabilized sludge from the first pilling zone into the 2 08 442 -β * - "'" Berlin, d.8.3,1979 54 354/13 Azidification subzone is introduced there and remains for a sludge retention time 24 to 60 hours for the purpose of Sohlammazidifikation and the acidified sludge from the acidification sub-zone discharged and introduced into the methane fermentation sub-zone and there at a temperature in the range of 35 ° C remains to 40 ⁰ O v / during a mud retention time of 4 to 8 days. 21. The method according to item 20, characterized in that the sludge is maintained in the methane fermentation sub-zone at a temperature of 37 ⁰ C to 3S ° C. 22. A method according to Item 2O _9, characterized in that the sludge in the acidification zone is maintained at a temperature of between 45 ° C and 75 ° C and the acidified sludge discharged from the acidification zone is at a temperature of 35 ° C to 40 ⁰ C is cooled before the introduction into the methane fermentation sub-erfolgt one takes place. 23. A method according to any one of items 1, 2 or 3, characterized in that waste water containing biodegradable, suspended pesticides is treated to remove these pesticides from the effluent with the aid of the biochemical oxygen demand, including the following steps : Separating a primary sludge, consisting of the biodegradable, suspended pesticides, from the effluent for the purpose of obtaining a pesticide-depleted primary effluent; Mixture of primary waste water and circulation 2 08 442 - ^ 6- 16.7.1979 54,354 / Sludge and aeration at a sufficient rate and long enough to form a mixed fluid having a reduced biochemical oxygen demand; Separating the mixed liquid into a clean liquid and the activated sludge and recycling at least a major portion of the activated sludge to mix with the primary effluent to sludge to the broth, the primary sludge and the unreturned activated sludge the first Paulingzone in stage a) are fed as sludge feed. Method according to one of the items 1, 2 or 3, characterized in that the methane gas discharged from the second potting zone is mixed with the oxygen-containing gas and burned as heating gas to absorb the heat for the maintenance of the sludge in at least one of supply the first and second Paulungszonen at the elevated temperature. 25. Method according to item 24-, characterized in that the methane gas and the gas which has been separated from the acid gas are mixed and burnt as heating gas in order to maintain the heat for the maintenance of the sludge in the first potting zone at the temperature, in the range from 35 ° C to 75 C to deliver. 26. A method according to any one of items 1, 2 or 3, characterized in that the temperature of the slurry in the first potting zone is maintained in the thermophilic range of 45 ° C to 75 ° C and the temperature of the • Mud in the second zone of Pauling in the range of 16.7.1979 54 354 / 30 ° C to 6O ⁰ C is maintained. 27 · Procedure for the cleanroom saliva according to item 1, characterized by the following steps: a) Introduction of the sludge and the aeration gas, consisting of. at least 50% by volume of oxygen, in a first closed zone of pomace and mixture of the components in said first pilling zone in sufficient quantity and velocity for the purpose of aerobic digestion of the sludge, while the total of suspended sludge (IiLSS) of the sludge is of the order of at least .20000 mg / 1 is maintained; b) maintaining the sludge in the first potting zone during step a) at a temperature in the thermophilic range of 45 ⁰ C to 75 ⁰ C; c) plugging step b) during a sludge retention time (duration) of 4 to 48 hours for the purpose of partially reducing the sludge content of biodegradable, volatile suspended solids added to the first panning zone; ' _/ d) independently of each other, discharging the partially stabilized sludge and the sour-off-depleted Pauling gas having an oxygen purity of at least 21% from the first Pauling zone; 2 08 442 - "" '- 16.7.1979 54 354/13 e) introducing the partially stabilized sludge according to step d) into a second closed composting zone and f) maintaining the slurry (in the second Paulungszone under anaerobic conditions at a temperature of 30 ⁰ C to 60 ° C for a sufficient solids retention time) degradable for the purpose of further reducing the content of the sludge to biological, volatile suspended. Less than about 40 % of the biodegradable, volatile suspended solids content of the sludge to be fed to the first Pauling zone in step a), thereby producing methane gas and discharging the further stabilized sludge and methane gas from the second browning zone · 28. Sludge digestion method according to item 1, characterized by the following steps: a) introduction of the sludge and the aeration gas, consisting of at least 50 vol .-% of oxygen, as a flowing media in a first closed Paulungszone and mixing the components under • maintaining the content of gel'dstem oxygen (DO) of the mixed liquid to at least 2 mg / 1 and the total content of suspended. Sludges (MLSS) of the sludge of the order of at least 20000 mg / l; 08 442 - * ³ ~ 16.7.1979 54,354 / b) maintaining the sludge in the first potting zone during step a) at a temperature in the thermophilic range of 45 ° C to 75 ° C; (c) Step-setting b) (b) during a period of 4 to 48 hours for the purpose of partially reducing the sludge content of biodegradable, volatile, suspended pesticides supplied to the first potting zone; (d) Separate discharge of the partially stabilized sludge and the acidified impure gassing gas with an oxygen purity of at least 21 % from at least the first composting zone; e) introducing the partially stabilized sludge according to step d) into a second closed composting zone; and f degradable) maintaining the sludge in the second Paulungszone under anaerobic conditions at a temperature of 30 ⁰ G 60 ⁰ C (for a sufficient duration Peststoffretentionszeit) an.biologisch for the purpose of further reducing the content of the sludge volatile suspended Peststoffen to less as about 40 % of the sludge content. biodegradable, volatile, suspended zone in step a) and thereby formation, of methane gas and discharge of the still stabilized sludge and the methane gas from the second Paulingzone. - 2 08 442 ~ ³ ° - 16.7.1979 54 354/13 Process according to item 28, characterized in that the sludge fed to the first composting zone has a total content of suspended solids between 20,000 and 60,000 mg / l. Process according to item 28, characterized in that the sludge retention time (duration) of the sludge in the first digestion zone is 12 "to 24 hours. 31. A method according to item 28, characterized in that the sludge is heated prior to introduction into the first digestion zone in order to maintain the temperature in step b). 32. The method according to item 28, characterized in that the temperature in step f) in the range of 35 ⁰ C to 40 ⁰ C for the purpose of mesophilic digestion in the second digestion zone is maintained. 33. The method according to item 28, characterized in that the temperature in step f) for the purpose of thermophilic digestion in the second digestion zone in the range of 45 ° C to 5O ⁰ C is maintained. 34. A method according to item 28, characterized in that the sludge retention time (duration) of the sludge in step f) is sufficient to further reduce the sludge content of biodegradable, volatile, suspended solids to less than about 20 % of the content of the sludge on biodegradable, volatile, suspended solids, which was fed to the first digestion zone in step a). 2 OS 442 -31- 16.7.1979 54,354 / 35. The method according to item 28, characterized in that the sludge retention time (duration) of the sludge in
Stage f) is 4 to 12 days. 36. Method according to item 28, characterized in that each of the first and second panning zones has a surface / volume ratio of less than 0.08 ft ² / f V * , o The method according to item 28, characterized in that the sludge in the second Pauling zone by circulation of methane gas over the existing sludge
mixed, .. 38, method according to item 28, characterized in that the aeration gas is heated prior to introduction into the first zone of pollen in order to maintain the temperature in stage b) 39, method according to item 28, characterized in that the sludge prior to introduction into the first Pauling zone by an indirect heat exchange with a
further stabilized sludge coming out of the second zone of incineration is heated, 40, method according to item 39 », characterized in that the temperature in stage f) ranges from 35 ° C to
40 ⁰ C held and the heated mud of the other before the introduction of the first Paulingzone by a
Indirect heat exchange with the partially stabilized sludge coming out of the first Pauling zone is heated. 2 08 442 -92- 16.7.1979 ,. 54 3547 41. Method according to item 28, characterized in that the second "digestion zone consists of an acidification subzone and of a methane fermentation subzone
wherein the partially stabilized sludge from the first compaction zone is supplied to the acidification sub-zone and in this sub-zone during
a sludge retention time of 24 to 60 hours for the purpose of Schlammazidifikation remains, the
acidified sludge subsequently from the
Azidification sub-zone is discharged and in the
Methane fermentation sub-zone and there remains at a temperature of 35 ⁰ C to 40 ⁰ C during a sludge retention time 4 to 8 days. 42. A method according to item 41, characterized in that the sludge in the methane fermentation subzone is maintained at a temperature of 37 ⁰ C to 38 ° C. Method according to item 4-1, characterized in that the sludge in the acidification sub-zone is kept at a temperature of between 45 ° C and 75 ° C and the sludge
acidified sludge, which passes from the Azidifikations sub-zone to the discharge, is cooled to a temperature of 35 ⁰ C to 4O ⁰ C, before the introduction takes place in the methane of fermentation sub-zone. 44. The method according to item 28, characterized in that a waste water containing biodegradable, suspended solids is to be treated, with separation by means of the biochemical oxygen demand, which includes the following individual steps: 93-167.1979 54 354/13 Separating a primary sludge, consisting of the biodegradable, suspended pesticides, from the effluent for the purpose of obtaining a solids-depleted primary effluent; Mixing the primary effluent and circulating Schlainmes and aeration of these components at a sufficient rate and time sufficiently long enough to arrive at a mixed liquid with a reduced content of biochemical oxygen; Trenniaig of the mixed liquid in a purified liquid and an activated sludge and Recycling at least a major portion of the activated sludge to the zone of the primary effluent slurry as bubbling slurry, the primary sludge and the unreturned activated sludge being fed to the first digestion zone in stage a) as sludge therefor, Method according to item 28, characterized in that the methane gas which is discharged from the second digestion zone is mixed with the oxygen-containing gas and burned as heating gas in order to retain the heat for the maintenance of the sludge in at least one of the first and second digestion zones at an elevated temperature » 46 »Method according to item 4S", characterized in that 2 08 442 -aw- 16.7.1979 54 354/13 the methane gas and the oxygen-containing gas are mixed and burned as fuel gas to provide the heat for the maintenance of the sludge in the first Pauling zone at a temperature of 45 ° C Ms 75 ⁰ C. For this purpose__3 "pages drawings