WO2009118304A2

WO2009118304A2 - Method for processing domestic sewage from households

Info

Publication number: WO2009118304A2
Application number: PCT/EP2009/053420
Authority: WO
Inventors: Xiaohu Dai; Markus Gerlach
Original assignee: Bilfinger Berger Umwelttechnik Gmbh
Priority date: 2008-03-26
Filing date: 2009-03-24
Publication date: 2009-10-01
Also published as: DE102008002812A1; WO2009118304A3

Abstract

The invention relates to a method for processing domestic sewage from households, said sewage being conveyed by a vacuum sewage system and then being at least biologically or at least aerobically or at least aerobically treated. To make full use of the regenerative energy potential in the sewage and the biomass resulting from the sewage treatment, the domestic sewage is enriched with organic substances and is then supplied to a collection tank by means of a vacuum. The sewage is then aerobically pretreated in a first reactor, in which a three-phase separation is carried out by separately removing biogas, anaerobically pretreated sewage and incompletely digested sludge.

Description

description

Process for the treatment of domestic waste water generated in households

The invention relates to a process for the treatment of domestic sewage accumulating in households, which is conveyed by means of a vacuum sewage system and then treated at least anaerobically or at least aerobically or at least biologically.

A vacuum sewer system, i. The so-called vacuum sewer or vacuum drainage not only offers solutions for technical and topographical problems, but also offers the advantage that the accumulation of wastewater is reduced in comparison to conventional gravity sewerage. The waste water conveyed by means of the negative pressure prevailing in the vacuum sewerage is fed to a collecting tank, from which the wastewater is supplied to a conventional clarification, which is also used for the free fall channeling. In principle, the regenerative energy potential in wastewater and in the resulting biomass is not fully utilized.

DE-A-196 14 610 relates to a vacuum dewatering plant with which separate wastewater types of different composition are conveyed via one and the same line. For this purpose, various wastewater types are promoted at different times.

A vacuum dewatering plant according to DE-C-26 41 110 has line sections with a predetermined gradient or length dimensions.

DD 150 192 relates to a method of treating organic material in aqueous liquids. The wastewater is treated aerobically without the supply of external energy. DD 249 693 relates to a wastewater treatment in which first anaerobic and then an aerobic treatment is carried out in order to then return aerobic excess sludge obtained in a secondary clarification to the aerobic stage.

A process for the microbial degradation of organically contaminated substrates is described in DE-A-195 07 258. This involves a multi-stage concentration to be able to biodegrade residual and waste materials with a high concentration of solids to a very small residual amount.

DE-C-37 09 174 relates to a method and a device for the biological purification of organically contaminated effluents in which or the wastewater ingredients are microbially reacted under pressure and then separating the treated wastewater from the biological sludge by membrane or ultrafiltration he follows.

From DE-A-10 2005 063 228 a method for the purification of wastewater with an anaerobic biological treatment stage is known, wherein the anaerobic biological purification is carried out by means of biomass which is selected from psychrophilic microorganisms. In this case, sewage and kitchen waste are fed by vacuum sewerage in practice anaerobic cleaning.

A disposal concept, which is planned for Shanghai, China, provides that brown and black water is fed together with kitchen waste by means of vacuum sewerage a digester, using biogas produced to generate electrical energy or heat and used in the digester sludge as fertilizer becomes.

However, the prior art disposal concepts involving a vacuum sewer system do not fully exploit the energy potential in the wastewater and in the biomass. The present invention has the object of developing a method of the type mentioned so that the regenerative energy potential in the wastewater and the biomass resulting from the wastewater treatment is fully utilized. There is a desire to carry out an energy self-sufficient disposal.

According to the invention, the method is achieved essentially by the method steps

Enriching the domestic waste water with organic matter and transport of the enriched wastewater into a collecting tank by means of the vacuum wastewater system, anaerobic pretreatment of the enriched domestic wastewater in a first reactor, separate removal from the first reactor of biogas produced by the pretreatment, anaerobically treated wastewater and incompletely fouled sludge, whereby energy is recovered from the biogas, the anaerobically treated wastewater is aftertreated aerobically-biologically and the incompletely rotted sludge is anaerobically-biologically treated in a second reactor.

In this case, provision is made in particular for the domestic waste water to be supplied to rainwater from the first reactor under exclusion.

According to the invention, a supply concept is proposed which almost completely utilizes the domestic media of water and food, so that an energy self-sufficient system is formed in which the regenerative energy potential in domestic waste water is fully utilized. Emission or residues are avoided. In this case, according to the embodiments of the teaching according to the invention growing biomass can be used in addition. The same applies to rainwater, which is collected and guided in such a way that it is kept away from the first and second reactor, thus not affecting the biological purification of domestic waste water in the first two reactors, but can also be treated. An essential feature is the 3-phase separation in the first reactor, in which the domestic wastewater is treated anaerobically biologically. The disposal concept also offers the possibility that the treated wastewater streams are fed via irrigation or infiltration of the natural water cycle, so that the treatment effort for cleaning the respective wastewater stream is based on its degree of contamination. Environmental compatibility is maximized by near-zero emissions. Hygiene risks are excluded, provided that there is no direct reuse of the treated waste water.

To enrich domestic wastewater with organic components, kitchen waste is added to household gray and black water. For this purpose, the kitchen waste is previously crushed as shredded with a crusher installed in a drain. The wastewater is transported together with the kitchen waste in a service connection shaft and then in the sump of the vacuum sewer system by negative pressure. Through the use of the vacuum system and thus the installation of vacuum toilets in the home, the drinking water requirement for toilet flushing and the corresponding amount of waste water can be significantly reduced. Values of about 25% can be assumed.

To the vacuum system, the downpipes are not connected, so that only domestic wastewater is used, which is reduced in comparison to the usual gradient channeling in its volume and also enriched in terms of organic freight through the kitchen waste.

As a result, the concentrations of dissolved and solid organic ingredients in domestic wastewater increase, i.e., the wastewater is highly enriched with organics as compared to conventional domestic wastewater.

The domestic sewage is collected by means of the vacuum sewerage and then transported to a specially designed treatment plant for the treatment of domestic sewage, whereby neither rainwater nor other extraneous water enters the vacuum duct. tion. Thus, the domestic wastewater does not undergo dilution and remains highly enriched with organic matter compared to conventional wastewater.

In contrast, rainwater accumulated in settlements of roof and street drainage is collected separately and can be supplied to rainwater storage tanks in the usual way, in order then to be subjected to rainwater treatment, as will be explained below.

The concentration of domestic waste water offers the possibility of anaerobic wastewater treatment, which is carried out in the first reactor - also called anaerobic reactor - with integrated 3-phase separation. In this case, should be used as the first reactor, a high-load reactor or at least one that allows residence times of less than 24 hours at degradation rates of 60% - 80% of the organic load of domestic wastewater.

During the anaerobic biological purification fall in the anaerobic reactor separately biogas, an anaerobically treated wastewater and a not completely fouled sludge, the fiction, be further treated according to separately. Anaerobic processes form very little biomass compared to aerobic activation processes.

The anaerobically treated wastewater is then fed to a second biological treatment to remove residual degradable organic matter. As a result, a high elimination degree is achievable. The second biological treatment is carried out with the help of an aerobic biocynosis. In particular, a contact biology method is provided, in which the biomass is immobilized on carriers. Because of the anaerobic pretreatment, the oxygen demand and thus the energy consumption of the ventilation fan used is comparatively low. As a carrier material, a fixed bed, a fluidized bed or other regularly immersed contactors can be used.

Regarding regular contactors, the following should be noted. The bacteria are immobilized on carriers that are moved mechanically. The mechanical Movement of the carrier takes place, for example, by rotation, in particular when discs or drums are used as carriers of the biomass. Therefore, the term "rotating Biokontaktor" or "Biorotor" is often used.

Integral in and downstream of the contact biology process is a process for solids separation, such as biomass. Since comparatively small amounts of excess biomass are formed in the contact biology method, micro-screening, microfiltration or ultrafiltration can be used for solids separation, the separation being dependent on the requirements for the further use of the purified wastewater and thus the associated hygiene risk. The according to the process steps described above anaerobic biological, aerobiologically and mechanically clarified wastewater can then be used for example for irrigation to supply the nutrients still contained in the vegetation.

The solids resulting from the aerobic biological treatment or mechanical treatment are then fed to the second reactor which undergoes an anaerobic biological treatment of the incompletely fouled sludge being withdrawn from the first reactor.

Due to the combination of anaerobic pre-treatment, the aerobic aftertreatment with contact biology methods, in which only little excess biomass grows up, the sludge production is greatly reduced compared to conventional activation processes.

If it is intended that the clarified waste water taken from the anaerobic biological treatment stage be supplied to the water management, eg with treated rainwater, the anaerobically treated wastewater must be subjected to a further process step before the aerobic aftertreatment, in which nitrogen and phosphorus is removed, to eutrophication natural waters to prevent. The removal of nitrogen and phosphorus can be carried out biologically or chemically by precipitation. A precipitation of nitrogen and phosphorus may, for. B. by means the so-called MAP (magnesium ammonium phosphate) precipitation.

The incompletely fouled sludge resulting from the 3-phase separation in the first reactor is fed to the second reactor for anaerobic biological sludge digestion. In the second reactor, the separated biomass is introduced, which is obtained during the aerobic treatment of the anaerobically treated wastewater. In addition to these thin sludges, other dry biomass such as other organic waste from households, green waste or organic residues from agriculture can be fed to the second reactor, so that the combined organic waste thin sludge or biomass are digested in a co-digestion. Depending on the ratio between supplied sludge and supplied dry biomass results in a certain dry matter content for the sludge, which is fed to the total digestion. The dry matter content should be above 50 g / l. Consequently, sludge may need to be previously thickened or dry biomass previously suspended.

After the sludge digestion, the digested sludge, i. h., The fermentation residue mechanically dehydrated. Preferably, a combined sludge dewatering machine is used for thickening and dewatering to reduce the water content to the required extent.

A sludge dewatering machine is a compact system for the mechanical dewatering of sludges to achieve a degree of dewatering that goes beyond the purely static dewatering of gravity. For this purpose, forces are applied, which carry the water out of the mud. Decanter centrifuges use centrifugal forces. Chamber filter presses or belt filter presses use the mechanically applied pressure force and vacuum drum filters the atmospheric pressure force.

The dewatered fermentation residue should have a dry matter content of about 25%. Then the sludge is fed to a sludge drying plant to to be dried to a defined residual moisture content. The residual moisture content is determined by the nature of the intended use of the dried fermentation residue. A possible drying can be done by a solar drying, in which a large part of the drying takes place via the so-called glass effect.

For solar drying, the following should be noted. In this case, facilities for sludge drying are used, which use the so-called glass greenhouse effect, as this is to be found in glazed greenhouses. Sludge can be introduced through a moving floor in thin layers and slowly transported through the glass house with the help of a conveyor and turning system with harrow pins. The drying is done by the solar radiation and can be supported by floor heating.

In addition, a heater such as floor heating can be used, the waste heat can be supplied, the z. B. from the biogas or in the implementation of biogas is obtained.

The dried fermentation residues can be utilized in various ways. For example, dried fermentation residues can be burned as substitute fuels in industry or in power plants. For this purpose, it is necessary that the fermentation residues, which are preferably formed in pellets, have a residual moisture content of less than 10%. This value can easily be achieved by means of sludge drying, such as solar drying. If used in accordance with the digestate, the primary use of fossil fuels is reduced.

However, there is also the possibility of returning dried fermentation residues as nutrient fertilizer to agriculture. This corresponds to a purely material recovery. In this way, phosphate fertilizers from finite deposits and fossil primary energy consuming nitrogen fertilizers are replaced.

For agricultural utilization, there are several advantages to the disposal concept according to the invention: Heavy metal deposits from runoff are excluded, the transport costs of the digestate are greatly reduced after drying, the drying causes not only the digestion but also a significant sanitation of the digestate.

The biogas produced both in the first reactor and in the second reactor can be used in various ways, the possibilities depending on the power and heat demand in the sewage and sludge treatment or on the area from which the wastewater originates, ie from the Settlement area of households.

A direct utilization of the biogas is that a power generation takes place. A gas turbine or a combined heat and power plant can be used for this purpose. The resulting waste heat can be used to heat the anaerobic reactor (first reactor) or the digester (second reactor) and optionally still excess heat for sludge drying. If further excess heat is available, other heat consumers can be supplied.

As an alternative to the power supply, the biogas can be used directly as fuel. Thus, direct firing of a sludge drying plant can take place. Biogas utilization as fuel is also an option. For example, gas bottles can be bottled for household purposes or, after appropriate gas treatment, fed into a gas network. After further processing, further uses can be developed such. B. a plant for the production of fuel from biogas.

The rainwater accumulated in the houses should preferably be collected and treated in a decentralized manner in order to avoid a separate pipeline network of large total area and large pipe diameters. As a result, significant investment and operating costs can be saved.

For the treatment of contaminated rainwater, methods such as solid / liquid separation are used, in which both floating and sedimenting Be separated substances. Depending on the further use of rainwater fine cleaning can be done by micro sieve or microfiltration.

The treated rainwater can be temporarily stored in service water tanks. This process water can be used for exterior cleaning, street cleaning or fire extinguishing water. Excess operating water should be used for water management, d. h., seep into the groundwater or used in surface waters of recreational areas or discharged into rivers.

According to the invention, an urban supply and disposal concept with full utilization of wastewater and biowaste is made available. With the inclusion of rainwater, the concept almost completely utilizes rainwater and growing biomass to supply water and food as well as the naturally occurring media, so that the supply and disposal of a settlement with regard to the media mentioned results in almost no emissions and residues. Consumption of drinking water for the household and for public use in the settlement is reduced. The regenerative energy potential in water and biomass is fully utilized. This results in an energy self-sufficient disposal.

The wastewater streams are treated and fed via irrigation or infiltration of the natural water cycle, with the processing effort to clean the respective wastewater stream is based on its degree of contamination. The environmental compatibility is maximized by the almost zero emissions. However, in spite of extensive full utilization and almost zero emissions, there is basically no direct reuse, so that there are no hygienic risks that depend on the reliability of technical systems.

For more details, advantages and features of the invention will become apparent not only from the claims, the features to be taken these features - alone and / or in combination - but also from the following description of the drawing to be taken embodiment. The single figure shows a schematic representation of an urban disposal and supply concept for a settlement that encompasses a large number of houses. The term "settlement" should not be understood as limiting, but may also include villages or cities.

About a vacuum sewer system - also known as vacuum sewer 12 - the incurred in the houses 10 water, ie gray and black water, and crushed kitchen waste 16 are fed via vacuum lines 18 to a collecting tank 20.

From the collecting tank 20, the domestic waste water thus collected is supplied to a first reactor 22 via a pipe 24 in which anaerobic biological treatment with 3-phase separation takes place. The reactor 22 is in particular a high-performance reactor or at least one reactor in which, with a residence time of less than 24 hours, a decomposition rate of 60% -80% of the organic freight is made possible.

In the first reactor 22 or anaerobic reactor fall separately biogas, anaerobically treated wastewater and not completely fouled sludge, the fiction, be further treated according to separately.

The anaerobically treated wastewater is supplied via a line 26 to a second biological treatment stage 28 to remove residual degradable organic matter. The second biological treatment takes place with the aid of an aerobic biocyne, preferably a contact biology method 30, in which the biomass is immobilized on carriers. Because of the anaerobic pretreatment, the oxygen demand and thus the energy consumption for the ventilation fan is comparatively low. As a carrier material, a fixed bed, a fluidized bed or other regularly immersing contactors can be used. With the corresponding contact biology method 30 comparatively little excess biomass is formed. In process stage 28, which includes contact biology 30, a solids separation stage 32 may be integrated or connected. This may in particular be a micromachine rosiebung, a microfiltration or ultrafiltration for solids separation act. The thus anaerobic-biological in the reactor 22, aerobic-biological in which by the contact biology (step 30) and mechanically by the micro-screening (step 32) by means of z. B. microfiltration or ultrafiltration clarified wastewater can then be used directly for irrigation to supply the still contained valuable vegetation (compound 34 to the vegetation).

The solid fraction obtained in the treatment stage 28 is supplied via a line 36 to a second reactor 38, in which an anaerobic biological treatment takes place. In the reactor 38 also opens a line 40, which emanates from the first reactor 22, and over which the resulting in the anaerobic treatment of domestic sewage incomplete fouled sludge is fed.

In other words, the sludge from the anaerobic reactor 22 and the sludge from separated biomass are fed to the aerobic treatment 28 for sludge digestion in the second reactor 38. These Dünnschlämmen dry biomass such. B. other household organic waste, greenhorns from the settlement or organic residues from the surrounding agriculture to be referred to as a digester to be designated second reactor 38 to auszufaulen the combined organic waste and biomass in a co-fermentation. The addition of dry biomass is symbolized by line 40.

Depending on the ratio between supplied sludge and supplied dry biomass results in a certain dry matter content for the sludge, which is fed to the total digestion. The dry matter content should be above 50 g / l, so that, if necessary, sludges are previously thickened or dry biomass is previously suspended.

The digested sludge, ie the digestate, is then dewatered and dried to the required extent in a sludge dewatering machine 42. In order then additionally to be dried for setting a desired residual moisture content in a system 44 such as solar drying plant. In the solar drying plant 44 Drying takes place according to the so-called glasshouse effect. Furthermore, over existing in the system 44 heaters additional heating and drying can be done. In this case, the heating, such as bottom heating 46, can be supplied with waste heat via a line 48 which originates from a utilization device 50 for the biogas originating both in the first reactor 22 and in the second reactor 38.

The dried residues dried in the drying unit 44 can then be dried, e.g. are fed via a conveyor 51 a silo 52, from which the digestate are removed. Previously, the fermentation residues can be pressed in pellet form.

A use of the dried fermentation residues can be done directly in the form of agricultural utilization, as a nutrient fertilizer, or as a substitute fuel in industrial and power plants.

The biogas produced from the first and second reactors 22, 38 are supplied via lines 54, 56 to the gas utilization device 50. This may be e.g. in the event that it is a biogas power generation, to act as a gas turbine or a combined heat and power plant. The resulting waste heat can then be used to heat the anaerobic reactor (reactor 22) or the digester (reactor 38). However, the heat can also be used for the solar drying plant 44 or for other heat consumers.

Alternatively, the biogas can be used directly as a fuel. One example is the direct firing of a sludge drying plant. It is also possible to fill in gas bottles or to feed into a gas network after a gas treatment has taken place.

The rainwater accumulating in the houses 10 is supplied via lines 57 to a solid / liquid separation plant 58, in which both floating and sedimenting substances are separated off. The solid / liquid separation unit 58 may optionally be followed by a microsieve or microfiltration device 60 in order to carry out a fine cleaning. The treated rainwater can be temporarily stored in service water tanks and used for exterior cleaning, street cleaning or extinguishing water. Excess operating water is supplied to the water management, ie seeps into the groundwater or used in surface waters of recreational areas or discharged into rivers.

If purified domestic wastewater is also to be supplied to the treated rainwater, it is necessary that these be freed from nitrogen and phosphorus. For this purpose, it is provided that in the anaerobically pretreated wastewater taken from the first reactor 22 via the line 26, a precipitation of nitrogen and phosphorus by means of the so-called MAP precipitation is carried out before being fed into the aerobic biological treatment stage 28.

The floats of the rainwater treatment, ie those obtained in the solid / liquid separation stage 58, can be supplied to the second reactor 38. The sediments and residues from the rainwater treatment solids separation (step 58) are dewatered and dumped, as there is a possibility of increased levels of heavy metals.

Since all three phases of the anaerobic reactor 22 are treated further, there are no residues.

The thin sludge or the concentrate from the solids separation of the aerobic treatment 28 of the domestic wastewater is fed to the second reactor 38.

All wastewater from any required pre-thickening, post-thickening, dehydration and drying of the digestate are recycled to the inlet of the first reactor, ie the anaerobic reactor 22.

Claims

Claims: Process for the treatment of domestic waste water generated in households

1. A process for the treatment of domestic wastewater generated in households, which is conveyed by means of a vacuum wastewater system and then at least biologically or at least anaerobically or at least treated aerobically, characterized by the process steps:

2. The method according to claim 1, characterized in that the domestic wastewater is enriched organically by crushed kitchen waste.

3. The method according to claim 1 or 2, characterized in that foreign and rainwater is kept away from the transported by means of the vacuum sewage system and then the first reactor supplied enriched domestic sewage.

4. The method according to at least one of the preceding claims, characterized in that the enriched domestic wastewater over a period t in the first reactor anaerobic biologically pretreated with t <24 h, wherein the first reactor is operated such that during the pretreatment time organic Solids between 60% and 80% are degraded.

5. The method according to at least one of the preceding claims, characterized in that mesophilic or thermophilic conditions are set in the first reactor by supplying heat.

6. The method according to at least one of the preceding claims, characterized in that the withdrawn from the first reactor anaerobically treated wastewater by means of an aerobic biocynosis, preferably by means of contact biology method, aftertreated.

7. The method according to at least claim 1 or 6, characterized in that the aerobic-biological post-treatment is carried out in a fluidized bed, a fixed bed reactor or in a reactor in which immerse in the wastewater contact pores.

8. The method according to at least claim 6, characterized in that from the aerobically treated wastewater solids are preferably separated by Mirkosiebung, microfiltration or ultrasonic filtration.

9. The method according to claim 8, characterized in that the separated solids are fed to the second reactor.

10. The method according to at least claim 5, characterized in that the aerobically treated wastewater after separating the solids, e.g. used for irrigation.

11. The method according to at least one of the preceding claims, characterized in that at least nitrogen and phosphorus are precipitated from the anaerobically pretreated domestic wastewater and before its aerobiological aftertreatment.

12. The method according to claim 11, characterized in that the precipitation takes place by MAP precipitation.

13. The method according to at least claim 1, characterized in that in the aerobic aftertreatment, a biological nitrogen and phosphorus elimination is integrated.

14. The method according to at least one of the preceding claims, characterized in that the second reactor additionally dry or suspended biomass is supplied.

15. The method according to at least claim 1, characterized in that the separated from the aerobic-biologically treated wastewater solids are fed to the second reactor.

16. The method according to at least one of the preceding claims, characterized in that mesophilic or thermophilic conditions are set in the second reactor by supplying heat.

17. The method according to at least one of the preceding claims, characterized in that a partial stream of the second reactor removed digested sludge (digestate) is returned as contact sludge in the inlet of the first reactor.

18. The method according to at least one of the preceding claims, characterized in that the digested sludge (fermentation residue) taken from the second reactor is dehydrated and dried.

19. The method according to at least claim 18, characterized in that the digested sludge is thickened or dehydrated at least to a dry matter content of about 25% and then dried.

20. The method according to at least claim 18, characterized in that the drying is carried out by solar drying.

21. The method according to at least claim 18, characterized in that the dried digested sludge is used as fuel.

22. The method according to at least claim 18, characterized in that the dried digested sludge is used as nutrient fertilizer.

23. The method according to at least claim 18, characterized in that the dried digested sludge is pressed into pellets.

24. The method according to at least claim 1, characterized in that the withdrawn from the first reactor and the second reactor biogas is used for power generation or as a fuel.

25. The method according to at least claim 24, characterized in that the biogas is fed to a gas turbine or a combined heat and power plant.

26. The method according to at least claim 24, characterized in that in the power generation of the biogas resulting waste heat for heating the first and / or second reactor and / or for drying the digested sludge is used.

27. The method according to at least one of the preceding claims, characterized in that the remote from the domestic sewage rainwater is spread by solid / liquid separation.

28. The method according to at least one of the preceding claims, characterized in that the treated rainwater is subjected to a fine cleaning such as micro-sieving or microfiltration.

29. The method according to at least one of the preceding claims, characterized in that the treated rainwater is preferably collected and used for exterior cleaning or street cleaning or fire extinguishing water.

30. The method according to at least one of the preceding claims, characterized in that the treated rainwater is fed to a water management.

31. The method according to at least one of the preceding claims, characterized in that in the rainwater treatment resulting flotate is fed to the second reactor.

32. The method according to at least one of the preceding claims, characterized in that in the rainwater treatment resulting sediments and / or residues from the solids separation of the rainwater treatment are dewatered and deposited.

33. The method according to at least one of the preceding claims, characterized in that waste water from any required pre-thickening, a post-thickening, dewatering and / or drying of the digested sludge are fed to the first reactor.

34. Urban disposal and supply system for the treatment of domestic wastewater generated in settlements using a method according to any one of claims 1-33.