DD299583A7 - PROCESS FOR THE MESOPHILIC OR THERMOPHILIC AEROB-ENZYMATIC CONDITIONING OF LIQUID ORGANIC MATERIALS - Google Patents

Abstract

The invention relates to a method for mesophilic or thermophilic aerobic-enzymatic conditioning of liquid organic substances. The invention describes the conditioning of liquid organic matter and biomass, in particular of municipal sewage sludge with the aid of chelating agents and enzymes. According to the invention, the decomposition process of the organic substance in the aerobic conditioning reactor, with the addition of chelating agents and enzymes, is stopped after a period of 0.5 to 20 hours before complete dissolution thereof. Subsequently, the mixture is exposed to an unexposed, open post-reaction phase of 5 to 15 hours, where a biogenic flocculation takes place. Subsequently, a solid-liquid separation is performed. Conditioning agents can be added to speed up the postreactions. The biogenic flocculation and the degassing in Nachreaktionsbehaelter can be improved by stirring or a temperature increase. The dewatered sludge has a high calorific value. It is good for agriculture. {Conditioning; sewage sludge; enzymes; chelating agents; Flocculation, biogenic; Solid-liquid separation; aerobic; organic substance; biomass; post-reaction; Calorific value}

Description

Field of application of the invention

The invention relates to the conditioning of liquid organic substances, in particular municipal sewage sludge with the aid of chelating agents and enzymes.

Explanation of the known prior art

The methods of sludge treatment using enzymes which have been known for some years allow a significant reduction in the stabilization times compared to conventional methods. The patent literature includes several methods that describe the degradation of organic matter using enzymes in a particular amount based on the weight of the dry matter. The object of the known enzymatic processes is to reduce the activated sludge to be treated as quickly as possible to a stabilized form. It should be achieved with small amounts of alien enzymes high degradation performance with positive influence on the dewatering properties of the enzymatically treated sludge.

In the process according to patent specification GB 1563335, 0.001-15% finely divided dry matter and up to 5% of the tropic substance added enzymes and thermophilic microorganisms are fed into a reaction vessel and aerated,

wherein the sludge is continuously maintained at a temperature of 50 to 70 ° C. .

DE 2633514 relates to a process for increasing the filterability and sedimentation tendency of a slurry, wherein an enzyme or an enzyme group is added to the slurry with stirring.

No. 4,269,049 describes the conversion of treated sludge into utilizable substances by hydrolysis of the organic material present in the sludge by adding at least one hydrolytic enzyme and hydrolytic enzyme-producing microorganisms to the sludge, self-leaching of at least one sludge with enzymes or microorganisms and then separation of the slurry into sludge a drain and a moist product.

According to DD WP 234571 a method is known in which the enzymatically treated organic matter and the biomass are fed to a reaction medium which, depending on the nature and composition of the enzymatically

0.01 to 1 wt% of added hydrolytic enzymes and 0.005 to 0.5 wt% of a chelating agent, based on the mass of the organic dry substance and having a temperature of 30 to 60 ° C.

The reaction medium is an aqueous solution of enzymatically already treated organic substances, such as sewage sludge or Güllle or biomass, such as activated sludge or microorganism cultures.

If organic substances and biomass are added to this reaction medium, the hydrolysis of the organic macromolecules contained in the organic substances and the biomass (carbohydrates, proteins, fats) quickly leads to microbially readily usable low molecular weight compounds (sugars, organic acids ). These are immediately available for use with the organic substances and the microorganisms supplied to the reaction medium as biomass, so that their biochemical activity is thereby stimulated. The chelating agent contained in the reaction medium influences the metabolic activity of the microorganisms in such a way that, by virtue of its permeabilizing action, it triggers a strong unilateral promotion of its respiration and accelerates the mass transfer through its cell walls.

Due to the sudden supply of at least 10 ° C Lower temperature level having organic matter and the biomass in the 30 to 6O ⁰ C warm Reaktionsmeoium it occurs due to the temperature shift occurring

Increased release of exoenzymes by the microorganisms to the reaction medium and the dissolution of Prozessoner for microorganism self-dissolution (autolysis) and for Mikroorganismenversporung. The additive action of the hydrolytic enzymes, the chelating agent and the temperature shift achieves rapid degradation of biodegradable substances and of biomass or increased mass transfer through the microorganism cell walls as well as increased metabolite production of their metabolism (enzymes, vitamins, organic acids, antibiotics and the like).

For the drainage of sludge from sewage treatment plants, in addition to the natural drainage known as well Centrifuges applied as a method of mechanical sludge dewatering. The use of larger quantities "

polymeric flocculant is required to obtain a relatively high solids concentration in the centrifuge discharge and the lowest possible centrate concentration.

Statements on the drainage behavior have so far only been obtained by expensive large-scale drainage experiments

become. The parameters previously determined on the laboratory scale (filter resistance, CST value, etc.) allowed only limited assessment of the drainage behavior. By means of granulometric measurements and the detection of the surface potential, on the other hand, state statements are obtained which allow an estimation of the dewatering result.

Despite the use of costly flocculants often no dry matter content is achieved in Zentrifugenaustrag, the

allowing subsequent sludge incineration without additional fuels.

Sludge incineration reduces the volume of sludge to a minimum. The remaining ash is sterile

and can easily be eliminated forever. In the known methods of sludge incineration is both fresher

Activated sludge supplied to the combustion, which usually significant amounts of additional fuel are required, as well

rotten mud.

The burning of digested sludge requires extra energy; if the water content of the sludge cake too

is high. For starting, an additional fuel is necessary in any case. Substantial expenditure on additional fuels and

Energy is the well-known methods of sludge incineration to become a costly procedure, the

but not least for territorial landfill problems present and future.

It is known from DE 3429055 a method for the removal of sludge, especially sewage sludge, wherein a part

of Dickschlammes Pre-dried in a dryer to a certain dry matter content and the remaining

Dickschlamm is burned under supply of the dry material. DE 2916216 describes a process for the utilization of sludges, in which the sludge thickened, with the addition of a

conditioned amount of fine coal, then fed to a filter press and then ashed, is.

The identified disadvantages in the treatment of sludges with regard to their preparation for incineration would be

influenced by the latter method only partially positive.

Object of the invention

The aim of the invention is to minimize the expenditure for a sludge removal with a short reaction time and using the smallest amounts of chemicals. The end products resulting from the treatment should be readily usable in agriculture or their calorific value should be high.

Excitement of the essence of the invention

The object of the invention is to develop a process by which liquid organic substances, preferably sewage sludge, are treated with an extremely short reaction time and using chelating agents and enzymes in such a way that their particle sizes and surface activities enable mere flocculation and the solids in a downstream dewatering step from the liquid phase can be easily separated. The end products should be readily self-compostable or combustible with a high calorific value. '

According to the invention the object is achieved in that the liquid organic substances to be treated in a known manner in a bioreactor with 0.001%, based on the organic content of the dry matter, a chelating agent, preferably a salt of nitrilotriacetic acid and with 0.001 to 1.5%, based on the organic portion of the dry matter, a the organic components of the contained solids-cleaving enzyme or enzyme mixture - / replaced and aerated intensively. In this phase, the organic substance is broken down into smaller sludge particle sizes and higher specific particle surface areas while at the same time increasing the surface activity. According to the invention, the process of splitting the substance is stopped when about 30 ... 50% of the particles <1 μπι and 40 ... 70% of the particles <5μηι, and the value of the surface charge of the sludge particles to raw sludge by about 15 ... 30% higher. At this time, the sludges still have a high dispersion stability. This happens after a reaction time of 0.5 to 20h. The mixture thus treated is then exposed in a downstream reactor an unventilated post-reaction phase of 5 to 15 h. The possibility of degassing is provided, which is achieved by an open design of the post-reaction tank. In this post-reaction phase, the biogenic flocculation of the surface-active sludge particles takes place with simultaneous de-stabilization of the dispersion. In order to optimize the subsequent mechanical dewatering optimally, the after-reaction should be stopped if only 15.sup.-20% of the particles are less than 1 .mu.m and 30-40% of the particles are less than 5 .mu.m, the surface charge simultaneously passing through a minimum. The remaining difference in surface charge to the setting of the isoelectric point can be done in the interest of further reducing the use of polymeric flocculants in contrast to the usual practice by adding suitable inorganic substances. Subsequently, a solid-liquid separation by known means, for. B. with decanter centrifuges or gravitational thickening.

To accelerate the aggregation and shorten the post-reaction time, the post-reaction phase in an elevated temperature range of 20 ... 38 ⁰ C or 45 ... 75 ° C take place. The temperature increase causes a lowering of the surface tensions, whereby the degassing is accelerated. At the same time, the stability of the flakes is increased. Furthermore, a partial stream of the substance mixture to be treated can be withdrawn before the aeration and processed in such a way,

that the contained self-enzymes are released, which z. B. can be done by means of ball mills. Subsequently, this partial stream is also fed to the aerobic reaction process. As a result, a reduction of Fremdenzymzugabe is achieved. The customization process is greatly accelerated by the addition of drugs (enzymes, chelating agents). In the course of enzymatic transformation processes, biodegradable substance is only partially eliminated (about 8% compared to about 30% for sludge digestion and about 15 to 20% for enzymatic sludge stabilization).

The temperature range required for the conditioning process in the aerobic reactor (25 ... 38 ⁰ C) is preferably achieved by utilizing exothermic metabolic processes of the microorganisms contained in the sludge. For this purpose, it is necessary to enter atmospheric oxygen by means of suitable gassing in the reactor and the reactor contents constantly mittefs suitable conveyors such. B. centrifugal pumps, circulate. Alternatively, said temperature range can be realized by supplying external energy into the aerobic reactor.

Ausführungsbetspiele The invention is explained in more detail below with reference to four examples. Raw sludge from a municipal wastewater treatment plant with a solids content of 4% is stored in a raw sludge stacking tank

homogenized. Subsequently, the raw sludge is quasi-continuously via a flexible pipe with inductive

Flow rate measurement and a Rohschlammbeschickungspumpe supplied to the aerobic conditioning reactor. In this case, the addition of 60 g of the triammonium salt of nitrilotriacetic acid which has been dissolved in about 30 l of tap water is carried out. Furthermore, per cubic meter of chelate-containing raw sludge, 60 g of tap water in about 100 times the amount

predissolved complex enzyme preparations containing ß-glucanase, amylases, proteases and lipases, constantly added. About one-tenth of the raw sludge is ball-milled before being added to the aerobic reactor. Here is the

Release of self-enzymes, which reduces the amount of foreign enzyme added. From an intensive aerator is

the sludge in the conditioning reactor continuously circulated and supplied with oxygen.

In the case of discontinuous aeration, circulation is additionally carried out by means of a centrifugal pump. The sludge temperature of the raw sludge is determined by the exothermic metabolic processes contained in the sludge Microorganisms increased from 20 ° C to about 3O ⁰ C and remains approximately constant. Through the biological metabolic processes

and the mechanical stress caused by the intensive aerator, a splitting of the organic substance into smaller

Particle sizes of the sludge particles and higher specific particle surfaces. The decomposition of the organic substance in the conditioning reactor is not carried out as in the enzymatic Sludge stabilization until its complete dissolution. The process is aborted after 4 hours. To this At the time, the reduced sludge particles have high surface activity. The thus pretreated sludge is after addition of cationic polymeric flocculation aids (Zetag 92, Fa. ACM / FRG)

transferred into an open post-reaction tank. There is an intensive aggregation of the sludge particles. Except the

Circulation accelerates the degassing by an increased temperature of about 38 "C by external heating. At the same time, this accelerates aggregation. After 10 hours Nachreaktionsdauer the treated sludge is fed to a mobile decanter centrifuge system and

dewatered.

The separation efficiency of the solids is 97-99%. The resulting sludge water with a dry matter content of

Less than 0.1% by mass of dry substance is fed to the feed of a wastewater treatment plant. The dehydrated

Sludge has a dry matter content of about 32% by weight of dry matter and thus a high calorific value, a

very crumbly structure and a low water absorption capacity. He is almost completely odorless. The height

Calorific value enables combustion without (self-sufficient combustion) or with greatly reduced use of additional

Energy.

Taking into account the Schwermetallgrenzkonzemration the dewatered sludge can with a high proportion P ¹ and N

be directly used, composted or landfilled.

Raw sludge of a municipal wastewater treatment plant with a solids content of 4% is stored in a raw sludge stacking tank

homogenized. Subsequently, the raw sludge is quasi-continuously via a flexible pipe with inductive

Flow rate measurement and a Rohschlammbeschickungspumpe supplied to the aerobic conditioning reactor. In this process, 60 g of the triammonium salt of nitrilotriacetic acid which has been dissolved in about 301 tap water are added. Furthermore, per cubic meter of chelate-containing raw sludge, 60 g of tap water in about 100 times the amount

predissolved complex enzyme preparations containing ß-glucanase, amylases, proteases and lipases, constantly added. About one-tenth of the raw sludge is ball-milled before being added to the aerobic reactor. Here is the

Release of self-enzymes, which reduces the amount of foreign enzyme added. From an intensive aerator is

the sludge in the conditioning reactor continuously circulated and supplied with oxygen.

In the case of discontinuous aeration, circulation is additionally carried out by means of a centrifugal pump. The sludge temperature of the raw sludge is determined by the exothermic metabolic processes contained in the sludge Microorganisms increased from 20 ° C to about 3O ⁰ C and remains approximately constant. Through the biological metabolic processes

and the mechanical stress caused by the intensive aerator, a splitting of the organic substance into smaller

Particle sizes of the sludge particles and higher specific particle surfaces. The decomposition of the organic substance in the conditioning reactor is not carried out as in the enzymatic Sludge stabilization until its complete dissolution. The process is aborted after 4 hours. To this At the time, the reduced sludge particles have high surface activity. The pretreated sludge is transferred to an open post-reaction tank. Due to the high surface activity

The sludge particles undergo a back aggregation of Schiammteilchen. Due to the fine primary particles formed during the reaction phase, shear-stable agglomerates can thus be formed. The degassing is increased by a

Temperature of about 38 ⁰ C accelerated by foreign heating. At the same time, the aggregation proceeds faster. To

After 10 hours post-reaction time, the sludge is treated with cationic polymeric flocculants after addition of primary flocculants (FeCl ₃ ) (Zetag 92, ACM / FRG) and dewatered by machine (eg decanter).

The degree of separation of solids is 97-89%. The resulting sludge water with a dry matter content of less

as 0.1% by mass of dry substance is fed to the feed of a wastewater treatment plant. The dewatered sludge has a dry matter content of about 32% by weight of dry matter and thus a high calorific value, a very crumbly structure and a low water-repellency. He is almost completely odorless. The high calorific value enables combustion without (self-sufficient combustion) or with greatly reduced use of additional energy.

Taking into account the heavy metal limit concentration, the dewatered sludge with a high proportion of P and N can

be directly used, composted or landfilled.

Sludge of a municipal sewage treatment plant with persistent ingredients with a solids content of 3% is in one Homogeneous sludge stack container homogenized. Subsequently, the raw sludge is quasi-continuous via a flexible pipeline

with inductive flow measurement and a slurry feed pump to the aerobic conditioning reactor. In this case, the addition of 60 g of the preheated in about 3Ol tap water triammonium salt of nitrilotriacetic acid.

Furthermore, per cubic meter of chelating raw sludge 60g of one in about 1 (making amount of tap water

predissolved complex enzyme preparations containing ß-glucanase, amylases, proteases and lipases, en dosed constantly. About one

One-tenth of the raw sludge is ball-milled before being added to the aerobic reactor. Here the release takes place

of self-enzymes, thus reducing the amount of addition of foreign enzymes. From an intensive aerator, the mud in the

Conditioning reactor continuously circulated and supplied with oxygen. In the case of discontinuous aeration, circulation is additionally carried out by means of a centrifugal pump. The sludge temperature is determined by the exothermic metabolic processes of the microorganisms contained in the sludge

within 20 hours from 2O ⁰ C to 50 "C. The biological metabolic processes and the mechanical

Stress durr.'i the intensive aerator cause a splitting of the organic substance into smaller sludge particles

and higher genetic particle surfaces.

The pretreated sludge is transferred to an open post-reaction tank. Due to the high surface activity

The sludge particles undergo a back aggregation of the sludge particles. Due to the fine primary particles formed during the reaction phase, shear-stable agglomerates can thus be formed. By supplying external energy, the sludge temperature of 5O ⁰ C is kept constant, so that the aggregation proceeds faster. At the same time, therefore, the

Degassing speeds up. After 15 hours of post-reaction, the sludge with cationic polymeric flocculants (Zetag 92, Fa. ACM / FRG)

and dewatered by machine (e.g., decanter).

The separation efficiency of the solids is 97-99%. The resulting sludge water with a dry matter content of

Less than 0.1% by mass of dry substance is fed to the feed of a wastewater treatment plant. The dehydrated

Sludge has a dry matter content of about 32% by weight of dry matter and thus a high calorific value, a

very crumbly structure and a low water absorption capacity. He is almost completely odorless. The height

Calorific value enables combustion without (self-sufficient combustion) or with greatly reduced use of additional

Energy.

Taking into account the heavy metal limit concentration, the dewatered sludge with a high proportion of P and N can

be directly used, composted or landfilled.

Slurry of a pig farm with a solids content of 6% is homogenized in a container. Subsequently, will

the liquid manure quasi-continuously over a flexible pipeline with inductive Durchflußmengenmessung and a

Feeding pump fed to the aerobic conditioning reactor. The addition of 60g of the in about 3Ol LejtungswasservorstenstenTriammoniumsalzes the nitrilotriacetic acid. Furthermore, per cubic meter of chelating agent Slurry 60 g of a complex enzyme preparation predissolved in about 100 times the amount of tap water, the β-glucanase, Contains amylases, proteases and lipasone, constantly dosed. Approximately one-tenth of the slurry is aerobic before being added Treated reactor in a ball mill. Here, the release of self-enzymes, which is the addition of Fremdenzymen is reduced. From an intensive aerator, the liquid manure in conditioning reactor becomes continuous for 0.5 h

circulated and supplied with oxygen.

In the case of discontinuous aeration, circulation is additionally carried out by means of a centrifugal pump. The Temperature is due to the exothermic metabolic processes of microorganisms contained in manure sludge of 20 ° C.

about 3O ⁰ C increases and remains almost constant The biological metabolic processes and the mechanical stress caused by the intensive aerator, a splitting of the organic substance into smaller particle sizes along with a

Enlargement of the specific particle surface. The pretreated slurry is transferred to an open post-reaction tank. Due to the high surface activity of the Sludge particles undergoes a back aggregation of the sludge particles. Due to during the reaction phase

As a result, shear-stable agglomerates can be formed. The mud temperature is

an average of 25 ⁰ C. After 5 hours post-reaction time of the slurry sludge after addition of cationic polymers is

Flocculants (Zetag 92, ACM / FRG) and dehydrated by machine (eg decanter). The separation efficiency of the solids is 97-99%. The resulting sludge water with a dry matter content of less

as 0.1% by mass of dry substance is fed to the feed of a wastewater treatment plant. The dewatered sludge has a dry solids content of about 32% by weight dry matter and thus a high calorific value, a very crumbly structure and a low water-repellency. He is almost completely odorless. The high calorific value enables combustion without (self-sufficient combustion) or with greatly reduced use of additional energy.

Taking into account the heavy metal limit concentration, the dewatered sludge with a high proportion of P and N can

be directly used, composted or landfilled.

Claims (4)

-1- 299 G83 Claims: 1. A method for mesophilic or thermophilic aerobic-enzymatic conditioning of liquid organic materials and biomass, in particular municipal sewage sludge, wherein the liquid substances to be treated in an aerobic conditioning reactor with 0.001 to 0.1%, based on the organic content of the dry matter, of a chelating agent and from 0.001 to 1.5%, based on the organic content of the dry matter, of an enzyme or enzyme mixture which cleaves the organic components of the solids present and is intensively aerated, characterized in that the aerobic reaction process of the decomposition of the organic substance before its complete Resolution is terminated, at a time when 30-50% of the treated particles have a particle size less than 1 pm and 40-70% of the particles have a particle size less than 5 μηα, and the thus treated mixture then a non-aerated post-reaction phase of five to 15 hours which is exposed, at the same time allowing degassing. 2. The method according to claim 1, characterized in that a Teilstcom the liquid mixture to be treated is treated so that the self-enzymes are released and then this partial stream is fed to the aerobic Reaktionsprözeß. 3. Process according to claims 1 and 2, characterized in that the mixture before or during the Nachreakiionsi . * ^ Se conditioning agents, such as. As polymeric flocculants and / or precipitation chemicals can be added. 4. Process according to claims 1 to 3, characterized in that the post-reaction phase in an elevated temperature range, in the mesophilic or thermophilic range, proceeds.