DD289512A5 - METHOD FOR ANAEROBIC TWO-STAGE TREATMENT OF ORGANICALLY LOADED EQUIPMENT AND SLEEPING MEANS - Google Patents

Abstract

The invention relates to a method for the anaerobic two-stage treatment of organically contaminated waste water and Schlaemme. The load range of the 1st stage and 2nd stage is related to the solids present in the system as carriers of the biomass. The solids concentration in the reactors is independent of solids separation and solids recycling. As a result of solids import and Feststoffrueckfuehrung in the 1st stage of the solid is thickened, withdrawn as excess sludge and pumped to the 2nd stage, so that in the 1st stage independent of the stabilization a high solids loading is adjustable and in the 2nd stage stabilization takes place . {sewage; sludges; organic stress; Zweistufenprozesz; Substrate conversion; Stabilization; Roehrensedimentation; Solid enrichment; Biogas formation rate; thickening; Control; Load values}

Description

Field of application of the invention The invention relates to a method for the anaerobic two-stage treatment of organically contaminated wastewater and sludge, in

in the first stage a higher volume load is set.

The inventive method is particularly suitable for the treatment of municipal sludge. Characteristic of the known state of the art

The microbial degradation of organic compounds can be carried out either aerobically under oxygen supply or anaerobically under exclusion of air.

Anaerobic processes have a lower metabolic rate and require larger reaction volumes compared to aerobic processes. This stands opposite as an advantage of low energy consumption and an energy gain in the form of the methane gas formed in the process. An increased use of anaerobic processes requires the reduction of the reaction volume with a constant or increasing biogas yield.

In the vast majority of anaerobic processes for the treatment of municipal sludge, this is counteracted by the performance-limiting requirement for stabilizing the organic constituents. Within the framework of the snaercben process, the aim is to reduce the organic content of the dry matter (oTS) to 50 to 55%, which is achieved by a low volume load of organic dry matter, which depends on the system size 1.0 kg / m ³ d to 2 , 0kg / m ³ d. These low volume loads are associated with further increases in volume exceeding the metabolic rate specified, therefore, two-stage techniques have been developed which use a higher occupancy rate in the 1st stage and the ineffective one Simple structural design (eg in earthworks) and avoidance of biogas production often reduces the capital expenditure required for the second stage, and os is generally used to maintain a stable microorganism population. the rinsing losses of biomass due to the microorganism increase Thus, the residence time and, depending thereon, also the volume load in the methane fermentation is determined not only by the substrate degradation, but also by the microorganism growth rate. The low growth rates of the methane bacteria are followed by considerable reaction times in the methane fermentation. A shortening of the reaction times is only given if the Ausspülverluste limited to biomass or the flushed biomass are returned to the digestion process. For this purpose, in a number of methods, a biomass fixation on Befuchtsträger. In these fixed or fluidized bed reactors, however, solids in the substrate to be refined lead to considerable technical problems, so that an application of these methods remains limited to solids-free substrates. Other known methods work with a downstream sedimentation, with the aid of which the flushed biomass is separated and returned to the anaerobic process. Due to the high solids content in the municipal digestion process, this downstream separation stage can only act as a thickening. In the course of the thickening process, the overlapping flakes in the interior of the sludge layer generate an overpressure in the pore water, which is gradually reduced by pressing out the excess water from the sludge layer. This process takes a long time

Hindickzeiten. Associated with this are at low outside temperatures considerable heat losses and temperature differences between the digestion and the downstream sedimentation. As a result of these temperature differences to which the Menthan bacteria are exposed, the rate of reaction in the methane fermentation is reduced. In the course of thickening in municipal sludge a solids concentration of max. 60 kg TS / m ³ achievable. This concentration does not differ significantly from the solids concentration in the reactor, so that in a biomass recirculation, the population density in the methane fermentation is only slightly increased. To avoid these problems, a biomass separation is provided directly in the digester instead of the external sedimentation, with a waiver of a circulation targeted segregation in the reactor takes place, which allows a low-solids digester water discharge in the container surface. However, this means that the metabolic transport processes in the area of the bacterial cells and, depending thereon, the performance parameters of the overall system are adversely affected. There are also technical problems of effective control of the floating sludge blanket in the absence of recirculation. Reducing performance is also the fact that, regardless of the population density in the digestion process, compliance with the stabilization limit should be ensured by a minimal space load. Thus, the performance limits of the process are not clearly fixed. In addition, the separation of the anaerobic process into a highly loaded first stage and a subsequent low-load second stage prohibits the use of solids recycling, since the recycled to the high-performance stage and remaining organic solids must be stabilized and thus require the same low Haumbelastungen like that the second stage. Accordingly, the cTS space load of the first stage is also based on values Rb ^ 2.5 kg / m ³ · d. This corresponds approximately to a maximum oTS solids load of 0.05 kg / kg Ts · d. Methods are also known in which anaerobic circulation filters are operated with an organic loading of a 0.5, for example 8 or 16 kg COD / m ³ · day.

Object of the invention

The object of the invention is to increase the efficiency of methane fermentation, to further fix the performance limit of the process and to improve the efficiency through biomass recycling while saving energy, material and costs.

Explanation of the essence of the invention

The invention has for its object to set the maximum Lastberaich the first stage and the minimum load range of the second stage by the present in the system biomass solid mixture.

According to the invention, this object is achieved in that the first stage is driven with high substrate conversion and the second downstream stage with substantial stabilization of the organic substance, the solids introduced into the first stage and the biomass produced by the high substrate conversion in the reactor by means of the known Retained tube sedimentation and enriched, the solids are also carriers of the biomass and by targeted thickening by means of a controlled deduction of the biomass solid mixture solids-related performance limits for the first stage of max. oTS solid load S 0.12kg / kg TS · d and max. CSV _C , solids loading £ 0.09 kg / kg DM · d, and that with the solids removal the excess sludge solids mixture is pumped into the subsequent lightly loaded second stage for stabilization, the organic fraction being S 55% by regulation of the maximum load values of oTS solids load 0.025 kg S / kg TS d and CSVC, solids loading above 0.015 kg / kg TS · d is reduced.

The object of the invention is further solved in that the limits are set by the known per se tube sedimentation, the connecting lines are guided with an angle of inclination of 40 to 60 ° from below from the first reactor up into the second reactor and the ratio of length to cross-section of the connecting lines S is 8: 1.

In a further embodiment of the method according to the invention, the biomass-solid mixture of the first stage in the selected Feststoffabscheidesystem in cooperation with a known non-mixed thickening of 10% of the reactor volume is thickened to a solids content of about 10%.

The technical-economic effects of the invention, in particular its effectiveness, consists in increasing the efficiency of methane fermentation and in further fixing the performance limit of the process. The inventive method is further characterized by the fact that the efficiency is improved by the biomass recycling and material, energy and costs are saved.

exemplary

The invention will be explained in more detail below using an exemplary embodiment.

The urban wastewater of about 500,000EWG is to be treated by the process according to the invention in a municipal sewage treatment plant with mechanical-biological treatment. According to the standard WAPRO 2.19 / 01 of the VEB Kombinat Wassertechnik and Projektierung Wasserwirtschaft there is a daily sludge accumulation with a dry matter quantity of 85g / Ed · 500000EW = 42500 kg / d or an oTS-attack of 61 g / Ed · 500000EW = 30500 kg / d » 30000kg / d. The volume requirement required for a mesophilic digestion at 3O ⁰ C according to the standard WAPRO 2.19 / 03 is ³ d with a given OTS fluff loading of 1.5 kg / m ³

V.rf = => 20000 m ³ digester 1.5

-3- 289 B12

When using the method according to the invention for the digestion of the oTS attack of about 30,000 (.g / Tg following Volume requirement determined. The daily amount of sludge is fed to a first digestion stage. The reactor is in accordance with WP 206365 with a Nachklärvorrichtung, consisting of several tubes, for the separation and independent repatriation of microorganisms

equipped with inanimate solids, the tubes at the same time as connecting lines to transport the

Liquid phase at an angle of 45 ° from below from the first stage reactor to the top of the second stage reactor

be guided and the ratio of length to cross section 12: 1.

By using the connecting line between the first and second stage for biomass separation and recycling

The rinsing losses of biomass are limited so that the rate of increase of biomass in the methane fermentation limits more the hydraulic throughput rate and hence the first stage performance parameters. The solids in the system serve as

Carrier of biomass. Thus, the solids are assigned to certain maximum and minimum load ranges in which Exceeding the process collapses or stabilization of the organic substance is no longer in the desired Scope takes place. Since the stabilization and associated with it the decrease of the organic substance only when falling below

a minimal load range becomes apparent, the oTS load as a performance parameter for the methane fermentation is only conditionally meaningful. Therefore, the characterization of methane fermentation is based on product formation and the concept of biogas formation rate as a new performance parameter of the methane bacteria is established.

As a carrier of biomass, the solids become performance-determining. Therefore, the connecting lines between the Reactors for solids separation and solids recycling can be used. The connecting lines can consist of a tube, several tubes or box sections and have one Inclination angle of 40 to 60 °, in the present example, as stated above, 45 °. At the chosen tube length to tube diameter ratio of 12: 1, but at least 8: 1, the solids settle

a very short sedimentation distance in relation to the surface and then reach the bottom of the

Connecting lines, from which they slip back into the reactor due to the selected angle of inclination. Due to the biomass increase, the solid import and the solids recycling in the first stage is a solid enrichment

to record. At maximum load ranges, a stabilization of these solids is a prerequisite for an odorless

Drying and deposition not given. Therefore, these solids are the first stage in the hopper of the heavily loaded Thickened reactor and then pumped over as excess solids in the second stage. Here is the complete Stabilization at low loads. This requires a largely thickening to a 10%. This is guaranteed Thickening due to the interaction of the selected separation system with the thickening zone in the reactor of the first stage,

for which 10% of the reactor volume is not included in the recirculation system.

In the present example, the setting of a dry matter content of 60 kg DM / m ³ in the reactor of the first stage

by the solids introduced in the first stage, which are generated by the high substrate turnover and by the

Tube sediment retained biomass and the controlled deduction of the biomass solid content with 10% TS

from the non-mixed lower thickening zone of the reactor, which is 10% of its volume.

The allowable OTS load of 0.12 kg / kg d of the first stage is followed by a required reactor volume of

., 30000kg oTS / d .... ₃

^{V 'rf =} ~ ^4170m ·

The biogas production rate is 37 l / kg d at the selected oTS load, but the theoretically possible biogas production at complete outgassing is 480 l / kg oTS. This results in 64% OTS sales in the first stage.

The biomass-solids mixture withdrawn from the first-stage reactor by pump from the thickening zone is over-pumped to the second-stage reactor for complete stabilization, ie, reduction of the organic fraction to less than 55%. This reactor is operated at low loads of <0.025kg oTS / kg · d and <0.015kg CSV _c , / kg TS-d. The dry matter content is likewise adjusted to 60 kg DM / m ³ d by means of the abovementioned secondary clarifier and the biomass-solid mixture fed from the reactor of the first stage. When the residual OTS content is converted and an OTS loading of 0.025 kg / kg · d is established, the required reactor volume for the second stage is about 7 200 m ³ . Thus, the required total volume including the necessary storage volume of 10% is about 11800 m ³ .

Claims (3)

1. A process for the anaerobic two-stage treatment of organically polluted wastewater and sludge, in which in the first stage a higher Raumbolastung is set, characterized in that the first stage is driven with high substrate conversion and the second stage with substantial stabilization of the organic substance in the first stage registered solids and the biomass produced by the high substrate conversion are retained and enriched in the reactor by means of the known tube sedimentation, wherein the solids are also carriers of the biomass and by targeted thickening by means of a controlled deduction of the biomass solid mixture solids-related performance limits the first stage of max. oTS solid load <0.12 kg / kg ds · d and max. CSV _Cr solids loading <0.09 kg / kg TS · d are set, and that with the solids removal the excess sludge solids mixture is pumped into the subsequent lightly loaded second stage for stabilization, wherein the organic content to S 55% by regulating the maximum load values of OTS solids loading S 0.025 kg / kg DM · d and CSV _Cr solids loading S 0.015 kg / kg DM · d is reduced. 2. The method according to claim 1, characterized in that the limit values are set by the tube sedimentation known per se, wherein the connection performances are guided with an angle of inclination of 40 to 60 ° from below from the first reactor up into the second reactor and the ratio from length to cross section of connecting lines § 8: 1 amounts to. 3. The method according to claim 1 and 2, characterized in that the biomass solid mixture of the first stage in the selected Feststoffabscheidesystem in cooperation with a known, non-mixed thickening of 10% of the reactor volume is thickened to a solids content of -10% ,