domestic biodegradable garbage

This invention regards to a method and device to treat the entire organic refuse of preferably domestic settlements, both liquid (sewage, primary-, secondary- and tertiary sewage sludge) and solid biodegradable garbage. The name of the invention is T&U BioConverter.

There are several large-scale sewage treatment methods and devices on the market. They have high running costs in common. The sewage sludge fermenting towers are running with a dry substance content between 3% and 5%. Financially, the utilisation of the biogas from the sewage is feasible from 50,000 PE (= Population Equivalents) upwards. Small scaled sewage plants (known as Schreiber Klaeiwerk, Schachtelbecken, vΕDEWA-Rundbecken, Essener Becken, Gegenstrom Rundbecken, Biosedimat, Gyromat S, Oxigest-Klaeranlage, Total-Klaeranlage, etc.) are rarely utilising the biogas. The anaerobic fermentation of the sewage sludge has its main purpose in sludge conditioning.

Thus the disadvantage of the existing large-scale and small-scale methods and devices of sewage treatment plants is the low yield of biogas and high construction and running costs.

General biodegradable garbage treatment methods and devices are aerobic composting, anaerobic fermentation and aerobic composting, and incineration or pyrolysis. Aerobic composting methods and devices are common in a large and small scale. In neraϋon, pyrolysis and anaerobic fermentation are common only in large-scale methods and devices. The anaerobic fermentation of biodegradable garbage is done in a liquid form with dry substance content between 8% and 12%, and in a wet form with a dry substance content between 25% and 45%. Both anaerobic fermentation methods are producing excess process water which is polluted and requires treatment.

The disadvantage of incinerating or pyrolysing unsorted garbage is the loss of fertilising substances, the toxic emissions and ashes, and the high energy demand to evaporate the water content which originally is 65% - 75% of the biodegradable garbage.

The disadvantage of large-scale fermentation and composting methods and devices of biodegradable garbage treatment plants are: a. the long ways of the biodegradable garbage, leading to a loss of volatile solids due to mic-

robiological activity and thus a loss of biogas. The state of art yield of biogas is normally around 110 Nm ³ per metric ton of biodegradable garbage. b. the additional demand of a waste water treatment plant on site.

It has been proposed, to build a sewage plant and a garbage treatment plant separated, but on the same site (Patent DE-2460480).

The disadvantage to treat sewage and biodegradable garbage in separated plants are: c. space demand in case of two separated plants is higher, d. costs for technical equipment for two plants are higher, and e. the volume and costs of two fermentation towers, one with a dry substance content of approx. 5%, one with approx. 10%, are high.

Patent DE-44 03 589 proposes to feed the shredded biodegradable garbage into already existing fermentation towers of sewage plants.

The disadvantage is the lack of the hydrolytic step as to improve the efficiency of anaerobic catabolism, besides the heavy development of floating sludge in the fermentation towers (disadvantageous volume - upper sludge surface ratio).

There are several patents referring to combined treatment of sewage sludge and biodegradable garbage. Patents DE-24 31 120, DE-29 09 515, DE-30 01 508, DE-30 46 646, DE-32 00 915 and DE-39 16 866 are describing methods, which are characterised in that the separated sludge together with the garbage undergoes a composting device without production of biogas. Patent OE-38 38 894 is proposing a mobile two chamber device for drying and aerobic thermal treatment. The disadvantages are here not to utilise the volatile solids of the organic matter as biogas.

There are also several patents referring to combined waste water and garbage treatment. Patents

DE-OS 22 60 616, DE-28 34 718 and patent DE-25 58 703 are proposing methods to separate the sludge and incinerate it combined with the garbage for the production of carbon, or activated carbon, which are then used again in the water treatment device as a filter, or being sold as activated carbon.

The disadvantages here are the high costs of the method. The evaporation energy of the sludge and garbage mixture is very high.

Patent DE-3428 716 is proposing an incineration of the sludge and garbage. Again the disadvantage here is the high costs factor.

Patent DE-38 38 894 is proposing a mobile disposal method for sewage sludge combined with the garbage. The disadvantage here is the restriction of the size of the plant.

Patents DE-36 27 253 and DE-38 43 789 are proposing a method for combined treatment of

preferably liquid manure and biodegradable garbage, which is characterised by a sedimentation step between the hydrolysis step and the methane fermentation step. The disadvantage here lies in the big volume necessary for the hydrolysis device, and the bad sedimentation characteristics of partly fermented sludge.

Patent DE-42 02 326 proposes a method which is characterised in that the liquid from the solid phase is separated. The solids are then treated aerobically and the liquid phase undergoes first an anaerobic phase and is finally treated aerobically. The disadvantage here is again the lack of biogas production.

Patents SHO 60-29 319 and HEl 1-60 313 (Japan) propose a method and device for decentralised and compact treatment of biodegradable garbage and sewage. Both patents disclose aerobic sludge and garbage treatment. As sewage treatment, a mufti staged activated sludge process is proposed.

The disadvantage here are the costs and the lack of biogas production.

Patent DE-42 02 327 A1 discloses a method and device for decentralised and compact treatment of sewage and biodegradable garbage which is characterised in single stage anaerobic fermentation of primary sewage sludge and biodegradable garbage with internal stirrer. To achieve an increase of the solubilization of eg. fibrous organic matter, a treatment with fluoride is proposed. To increase the anaerobic catabolic process, an addition of a stimulating agens is proposed. As a flotation save-all, a retaining mesh is suggested. As sewage treatment a multi-staged activated sludge process is proposed. The disadvantage here are the production of FCC, the lack of a hydrolytic step, the costly devices and running costs, and the tendency of clogging of the retaining mesh in the anaerobic reactor.

It is the object of the present invention to overcome the above disadvantages and to provide a method and device for the means for decentralised and combined treatment of domestic sewage and anaerobic treatment of domestic biodegradable garbage in one device by taking maximised usage of the solar thermal energy and the gassing pressure energy of the biogas. Furthermore, the invention of this method and device preferably keeps the space requirement, the construction and running costs of the treatment plant as low, and at the same time the output of useful products as high as possible as to improve the economical balance.

This object is fulfilled with the means of the claims.

As commonly known, the oxygen solubility in water is decreasing, and the catabolic microbiological efficiency is increasing, within the physiologic! ranges, with increasing temperatures . Additionally, the temperature differences in tropical areas are much less than in moderate climates. In Europe, for example, the air stream in trickling filters is often downwards during the day, and upwards during the

night due to the often found difference of 10°C and more between the waste water and air. In tropical areas, the temperature difference between waste water and air, as well as between day and night is much less. A result thereof in case of e.g. modem trickling filters with a high inner surface - volume ratio (over 180 rrf/m ³ ) in tropical areas is, that often large areas within the trickling filter are running under anaerobic conditions. This leads to a decreased efficiency of the water treatment facility, to offensive odour emission and to bad sedimentation properties of the secondary sedimentation step.

Generally, the antagonists oxygen solvability and microbiological activity in hot areas demand intense aeration in order to take advantage of the high microbiological activity.

Also in moderate climatic conditions, the subject matter of this invention achieves better resistance against cold temperatures during the winter due to the heat input and the restricted and controllable heat losses of the device according to the invention.

The chimney effect is caused by heat accumulation in a partly closed space, e.g. a pipe, which is resulting in an up^raft, caused t e lower specific weight of the warmed up liquid or gasiform substance.

A welcomed side effect of t^e chimney effect preferably used by the present invention is the utilisation of the primary waste water treatment device (in case of being a trickling filter, RBC process, etc.) as a piojogical ?ir filter to minimise the offensive odours caused by the sedimentation stages and the drain^qe and/or drying device.

The air stream of the chimney effect can additionally be used for supportive transportation of the floating sludge blankets of the two sedimentation stages to the blow off pipe.

Well known is the chimney effect of trickling filters. The excess heat gained by aerobic cataboiism creates an updraft in the trickling filter transporting oxygen into the filter. Purposeful strengthened usage of the chimney effect for water treatment can only be found in water desalination methods.

Hotels in tropical countries are producing a special garbage, which has similar characteristics in most cases of other tourist areas being investigated. The garbage has a high content of organic matter

(approx. 85% of fresh weight). Due to the left overs of e.g. buffets and restaurants the content of volatile solids (easy biodegradable material) is extraordinarily high. Additionally, the amount of fats and grease is due to the high excess production in the kitchen also extraordinarily high.

An other special characteristic is the high content of fresh garden and park foliage. Most parks and gardens in hotels are well-groomed and produce a high amount of fresh and green, but fibrous material.

A sufficient technical know-how of handling and running combined sewage and garbage treatment plants is normally not existing in tourist areas. Thus the device must be easy to handle and must be insusceptible against disturbances.

The common environmental consciousness is also poorly spread in most tourist destinations.

Advantage of the present invention is the profitability of the recycling system. Thus the method and device should be reasonably priced, the running costs should be minimised and the output of useful products should be maximised.

To integrate the method and device in several decentralised units in cities even in industrialised countries, the device should require as little space as possible. The separated treatment of the organic compound of municipal garbage combined with waste water treatment in one decentralised device with minimised construction and running costs can achieve profitability, and is additionally improving the energetic and financial balance as well as the long-term capacity of existing garbage incinerators.

The fundamental idea of the invention is a method and device for the means for combined treatment of preferably domestic waste water and of preferably domestic biodegradable garbage in one space saving device as to decrease construction costs and to decrease running costs by utilising solar thermal and gassing pressure energy and at the same time increasing the output of reusable and/or sellable products (biogas, compost, water) as to make environmental protection measures financially attractive.

The device is a compact plant, preferably comprising mechanical (rake, flat sand trap, two sedimentation stages), primary (BOD, and COD removal, nitrification) and secondary (denitrification and removal of phosphorus) means for water cleansing and the means for methane fermentation of primary sewage sludge, secondary bacterial sludge and tertiary excess sludge (optionally) combined with the shredded biodegradable domestic garbage and the drainage and/or drying of the fermented organic matter. The method and device for the means of sewage purification can be extended up to the production of drinking water.

In order to minimise the space demand of the invention and as to improve the biological efficiency of the means for primary waste water cleansing (BOD _s and COD removal, and nitrification) and thus the costs for its construction, as well as to minimise the space demand of the drainage and/or drying device, the device according to the invention is preferably built as a tower; thus utilising and strengthening the chimney effect, caused by heat accumulation under the transparent cover of the drainage and/or drying device as well as the microbiological excess heat caused by aerobic catabolism.

Preferably, the method and device for the means for combined treatment of domestic sewage and anaerobic treatment of domestic biodegradable garbage in one device is equipped with a continuously anaerobic reactor for domestic biodegradable garbage and primary and secondary

sewage sludge fermentation according to the functional principle of fixed dome plants, which are running very successfully even in rural areas of developing countries. The advantages of fixed dome plants are the reasonable construction costs, the process stability and easy control of the plant with the timing of the biogas release. A fixed dome plant comprises a closed anaerobic reactor, in which the developing biogas is accumulating at the top of the reactor, and tank for pressure equalisation of the closed anaerobic reactor, in which the sludge volume, displaced by the biogas accumulation in the anaerobic reactor, flows in. The displaced sludge volume flows back into the anaerobic reactor by releasing the biogas. The turbulence of the back and forth flow of the organic solution together with the inflow turbulence of the fresh organic matter is continuously stimng the sludge in the anaerobic reactor. To avoid sedimentation, both anaerobic reactor and pressure equalisation tank can have funnel shaped bottoms, with the blow off pipe end at the funnel top. A stirrer for the continuously anaerobic reactor can be added.

Furthermore, the device according to the invention is preferably equipped in the continuously anaerobic reactor with a floating sludge blanket blow off chamber and -pipe, and a floating sludge blanket transportation system, with which the sludge blanket is transported towards the blow off chamber on transportation bars, which are attached to the inner walls of the reactor, by utilising the changing sludge levels in the reactor caused by the produced and released biogas. This floating sludge transportation and removal device is useful due to the fibrous organic matter input.

Furthermore, the device according to the invention is preferably equipped with an inlet and mixing tank for the continuously anaerobic reactor, which simultaneously functions as a hydrolysis reactor.

Additionally, the device according to the invention is preferably executed in a way that no or a few electrical devices (e.g.. pump for a trickling filter, electric motor for a RBC tank, etc.) are necessary for the entire material flow within the device according to the invention. In case of waste water treatment with a non-technical and natural device (soil filter, fish tank, etc.) no electrical machine is necessary, and the energy consumption of the device according to the invention is zero.

The objects, advantages and characteristics of the invention will be shown and exemplified by means of the drawings.

Fig. 1 : Embedding of the device according to the invention in an exemplary treatment system

Fig. 2: Material flow in a device according to the invention

Fig. 3: Exemplary layout plan of a device according to the invention

Fig. 4: Exemplary construction plan of a device according to the invention

Fig. 5: Exemplary sedimentation device within a device according to the invention

Fig. 6: Exemplary sludge blow off device from sedimentation stage 1 and 2

Fig. 7: Exemplary continuously anaerobic fixed dome reactor

Fig. 8: Floating sludge blanket removal

Fig. 9: Floating sludge blanket removal

Fig. 10: Floating sludge blanket removal

Fig. 11: Floating sludge blanket removal

Fig. 12: Floating sludge blanket removal

Fig. 13: Cross section through the continuously anaerobic reactor

Fig. 14: Floating sludge blanket transport: Situation before gas release

Fig. 15: Floating sludge blanket transport: Gas release

Fig. 16: Floating sludge blanket transport: Gas released

Fig. 17. Floating sludge blanket transport: Situation before floating sludge blanket removal

Fig. 18: Floating sludge blanket transport: Floating sludge blanket removal

Fig. 19: Floating sludge blanket transport: Floating sludge blanket removed

Fig. 20: Airflow in an device according to the invention

Fig. 1 shows the embedding of the device according to the invention in a entire recycling system. The device according to the invention is combined in one building, which is the subject of this patent application: The design of the device according to the invention can be modified and embedded in a any treatment and or recycling system. The entire treatment system shown in Fig. 1 is only exemp¬ lary of the invention.

Fig. 2 shows the material flow within the device according to the invention in connection with the pollution source. Raw sewage is entering the first sedimentation device 2a, is then treated in the pri¬ mary treatment device 4 via the pump sump 3 and then flowing into the second sedimentation device 2b. There are three recycling possibilities. Recycling 1 gives the opportunity to treat the pre-treated secondary bacterial sludge containing effluent again in the primary treatment device 4. Recycling 2 provides the opportunity to treat the pre-treated secondary bacterial sludge free effluent (it has passed the secondary sedimentation device 2b) also again in the primary treatment device 4. The flooding arrow recycles the pre-treated effluent back into the first sedimentation device, thus prevent¬ ing odour emission as well. The pre-treated and sludge free effluent flows then into the secondary treatment device 8. From here, the effluent has recycling quality, and is pumped back to the user after chlorinating.

The sludge gained by the first 2a and second 2b sedimentation device are combined with the food waste (and fresh foliage from the garden) entering the hydrolysis and/or mixing tank 9. After

hydrolysis, the first step of catabolism, the organic solution flows into the meth ne fermenter 11. The fat and grease is directly fed into the methane fermenter, because the hydrolysis of fats and grease is the biochemical speed limiting step.

After fermenting with a composition specific retention time in the methane fermenter 11 , the organic solution is overflowing into the drainage and/or drying device 13. In case of a drainage device 13, the drained water is flowing back to the secondary treatment device due to the high COD/BOD ₅ ratio. The dried organic matter is then aerobically further biodegraded on composting heaps, from where it also can be fed back for reuse to the pollution source.

Fig. 3 shows an exemplary functional draft of the tower-like construction of the invention. The space demand of this draft is 0.05 m ² per PE (= population equivalents). It is referred to Fig. 2, and the list of devices. The thin arrows are representing the water flow, the thick arrows the sludge and garbage flow. The raw sewage is entering via inlet pipe 1a the first sedimentation device 2a, the primary 4 and secondary 8 treated effluent is eluting via outlet pipe 8a for further treatment or direct recycling after chlorinating. The shredded organic waste combined with the sludge are flows, mediated by gravity from the hydrolysis device 9 through the methane fermenter 11 into the drainage and/or dry¬ ing device 13. The primary 2a and secondary 2b sedimentation devices are here combined in one di¬ vided Dortmund Tank. The primary and secondary sludge are accumulating at the funnel top of the device. The methane fermenter 11 is build around the Dortmund Tank (2a and 2b), and the primary treatment device 4 is build on top of the Dortmund Tank (2a and 2b). All other devices ( Hydrolysis device 9, pump sump 3, secondary treatment device 8 and pressure equalisation device 12) are pre¬ ferably build around this central tower.

Fig. 4 shows the complete constructional plan of the exemplary draft of Fig. 3. It is referred to Fig. 2, Fig. 3 and the list of devices. There is provided a connection pipe δbfor flooding the first sedimen¬ tation device 2a with fresh, oxygen enriched pre-treated effluent for odour minimisation. Pipe 5a can achieve a close loop between primary treatment device 4 and the pump sump 3. The single com¬ pounds of the invention will be explained in the following drawings.

Fig. 5 shows the sedimentation unit with pump sump 3 and hydrolysis device 9. The raw sewage flows in through inlet building 1, connection pipe 1a into inlet cylinder 2a1. Here the effluent is forced to flow downwards, and then to flow upwards in sedimentation device 2a, and overflowing into the gutter 7a. The only outlet of gutter 7a is leading into the pump sump 3. After primary treatment 4 (see also Fig. 4), the pre-treated effluent flows in through inlet building 6, connection pipe 6a into inlet cyl¬ inder 2b1. Here also, the effluent is forced to flow downwards, then to flow upwards in sedimentation device 2b and then overflowing into gutter 7b. Gutter 7b has two outlets: Pipe 7c is feeding the

secondary treatment device 8 with the pre-treated, sludge free effluent for further treatment. Pipe 7e can achieve a close loop (if pipe 7c is closed) between pump sump 3, primary treatment 4 and sec¬ ondary sedimentation 2b. Both pipes 7e and 5a make the entire plant extraordinary flexible, and easy adjustable to different effluent quantities. The closed loop via pipe 7e is preferably used for flushing and cleansing of the primary treatment device 4. The outflowing pre-treated effluent quantities in case of pipe 7c and 7e being both open can be adjusted with a slider and different sashes. Indepen¬ dent from the position of the slider, 100% of the effluent quantity entering the system via inlet build¬ ing 1 is flowing off through pipe 7c. With the pipe 7e the hydraulic load of the primary treatment device 4 and the secondary treatment device 2b can be changed at the same time, whilst the pipe 5a (see Fig. 4) can change the hydraulic load of the primary treatment device 4 without affecting the secondary treatment device 2b. The adjustments of the different recycling rates according to the in¬ flowing waste water quantity can easily be automated with a water level sensor at the venturi chan¬ nel, electric controllable valves and sliders and a computer.

In both sedimentation devices, the primary sludge in 2a and secondary sludge in 2b are accumulat¬ ing at the funnel top.

Fig. 6 shows the sludge blow off devices of the sedimentation stages 2a and 2b. Both blow off de¬ vices are located besides the separation wall in the exemplary Dortmund Tank. Opening the valve of pipe 2a3 forces the primary sludge due to the water pressure of sedimentation device 2a to flow through pipe 2a2 into hydrolysis device 9. Opening the valve of pipe 2b3 forces the secondary sludge due to the water pressure of sedimentation device 2b to flow through pipe 2b2 into hydrolysis device 9.

Sewage sludge has a specific weight of 1.15 to 1.2, and sewage water a specific weight of approx.1.05. With a floater with a specific weight of 1.12, or other appropriate measurement devices, the sludge levels in both sedimentation devices 2a and 2b can be measured and the release can eas¬ ily be automated with the same tools (see explanations of Fig. 5) as well.

Fig. 7 shows the sludge and shredded biodegradable garbage treatment unit. As mentioned before (see Fig. 6), the sludges from sedimentation device 2a and 2b are flowing into the hydrolysis device 9. After adding the garbage, the dry substance content is approx. 15%. By releasing more sewage out of the sedimentation devices 2a and 2b, the dry substance content can be adjusted to around 10%. During hydrolysis the pH in the solution decreases from 7.5 down to 2.5. Due to the acid sensi¬ tivity of the methane bacteria in the methane fermenter, lime milk (CatOH)^, or other lye can be added as to neutralise the pH. Before releasing the organic solution into the methane fermenter 11 after a composition depending retention time for complete hydrolysis and eventually pH adjustment, the fats and grease are added. After stirring, the organic solution is fed into the methane fermenter

by opening the valve or slider of pipe 10. This pipe has preferably a diameter of at least 20 cm in order to achieve with a fast flow a high kinetic energy input into the methane fermenter 11 for inter¬ mixing the fermenting liquor. Additionally, the organic solution should be released after releasing the biogas from the methane fermenter 11 as to maximise the hydraulic drop between the hydrolysis de¬ vice 9 and the sludge level in the pressure equalisation tank 12. The bottoms of the hydrolysis device 9, as well as the methane fermenter 11 and the pressure equalisation tank 12 can be designed in a funnel shape with the outlet pipes at the funnel top as to avoid sediment accumulation. The hydroly¬ sis device can also be equipped with an active biomass retaining device as to improve the efficiency of the batch wise hydrolytic process. The entire anaerobic unit shown can also be designed for a con¬ tinuously material flow. This device can also easily be automated.

The series of Fig. 8 to Fig. 12 shows the accumulation of the biogas in the methane fermenter 11, and the press through of the floating sludge blanket (marked with FS in Fig. 8 and 9) from the meth¬ ane digestor into the equalisation tank 12. This process can also easily be automated with a pressure sensor and a floater on top of the floating sludge blanket as the only sensors in the methane fermenter.

Fig. 8 shows the anaerobic unit after biogas release. Due to the high hydraulic drop between the hy¬ drolysis device 9 and the sludge levels in the methane fermenter, this is the best moment, to release fresh hydrolysed material from the hydrolysis device 9 through pipe 10 into the methane fermenter 11 (see explanations of Fig. 7). The floating sludge blanket is accumulating at the top of the methane fermenter 11. The pressure equalisation tank 12 is empty.

Fig. 9 shows the accumulation of the biogas in the methane fermenter 11. The sludge level as well as the floating sludge blanket in the methane fermenter 11 drop, and the sludge levels in the pres¬ sure equalisation device 12 and in the floating sludge blanket removal channel 15 rise. The organic fermenting solution is pressed through connecting channel 14a from the methane fermenter 11 into the pressure equalisation tank 12. The sludge level in the pressure equalisation tank 12 has not re¬ ached the upper edge of the floating sludge blanket removal channel 15.

Fig. 10 shows the moment to release the biogas from methane fermenter 11. The sludge level in the pressure equalisation tank 12 and the floating sludge blanket removal channel 15 has reached the upper edge of the floating sludge blanket removal channel 15. The hydraulic connection from the methane fermenter 11 through channel 15 into the pressure equalisation tank 12 is open. The liquid sludge level in the methane fermenter has not yet risen so far to reach the lower edge of the floating sludge blanket removal channel 15.

Fig. 11 shows the situation, if the biogas after the moment, described in Fig. 10, is not released. The liquid sludge level in the methane fermenter drops under the lower edge of floating sludge blanket re¬ moval channel 15. Due to the lower specific weight of the biogas bubbles containing sludge particles, these particles are ascending. During ascent, the pressure of the surrounding liquid phase decreases. The biogas bubbles in the sludge particles are thus growing, so decreasing the specific weight of the sludge particles. Therefore a suction is developing in the floating sludge blanket removal channel 15 (symbolised with the bold arrow in floating sludge blanket removal channel 15).

Fig. 12 shows the situation after the floating sludge blanket removal. The sludge blanket is floating in the pressure equalisation tank 12. Now, only gas bubbles will pass through floating sludge blanket re¬ moval channel 15. This demonstrates the double function of the floating sludge blanket removal channel 15 as an overpressure valve as well. This is the moment, to release the biogas.

Fig. 13 shows a cross section through the methane fermenter. The hatched ellipse in the upper draw¬ ing indicates the cut level seen from top in the lower drawing. In the middle of the lower drawing the funnel top of the sedimentation devices 2a and 2b with the separation wall and the sludge outlet de¬ vices 2a2 and 2b2 are visible.

The hatched area indicates the cut through the methane fermenter 11. The material enters the meth¬ ane fermenter 11 via pipe 10. It flows with a composition speciflc retention time around the sedimen¬ tation device through channel 14a into pressure equalisation tank. There is a back and forth flow due to the production and release of the biogas. The dotted line with the arrows and the letter y and z is indicating the location of the cross section of the following Figures 14 to 19.

The series of Fig. 14 to Fig. 19 is showing the transport mechanism of the floating sludge blanket in the methane fermenter 11 towards the floating sludge blanket removal channel 15. The same trans¬ portation system is also installed in the pressure equalisation tank 12, but not shown in the figures. The left-hand drawings of the figures 14 to 19 are showing a radial cross section through the meth¬ ane fermenter 11 and the pressure equalisation tank 12, with the view towards the floating sludge blanket removal channel 15 and the end of the methane fermenter 11. At the bottom of the left draw¬ ings, the inlet of the connecting channel 11a is visible.

The right-hand drawings of the figures 14 to 19 are showing a tangential cross section through the methane fermenter 11, the connecting channel 11a, the floating sludge blanket removal channel 15 and the equalisation tank 12 with the view towards the outer wall of the methane fermenter. The floating sludge blanket transporting bars 16 are fixed at the inner and outer walls of the methane fermenter. As visible, the lower edge of the sludge blanket transporting bars 16 is horizontal increas¬ ing and the inner edge is vertically increasing.

If the sludge blanket is rising, the lower edges of the transportation bars 16 cut the sludge blanket and moves it during its rising towards floating sludge blanket removal channel 15. At the same time, the floating sludge blanket is compressed by the walls of the methane fermenter 11. If the sludge blanket drops, the transportation bars 16 and the walls of the methane fermenter 11 re¬ lease the floating sludge blanket. It is sliding downwards at the vertical edges of the transportation bars 16. The fibrous structure of the sludge blanket prevents a decompression of the sludge blanket. The slow drop of the sludge level due to the biogas production press it slightly towards the floating sludge blanket removal channel 15. The sludge blanket is also fixed during level drop due to the fact that the floating sludge blanket removal channel 15 sticks in the sludge blanket. The floating sludge blanket is drawn hatched, the liquid sludge is underlaied with black points. At the outer left and right side of each drawing, the liquid sludge levels are marked with triangles. Capital bold letters are indicating the levels in the pressure equalisation tank 12, small bold letters the levels in the methane fermenter 11. Broken triangular level marks with normal letters are indicating levels of the former drawings as to demonstrate the level differences.

Fig. 14 shows the situation before biogas release (see also Fig. 10 and explanations). The floating sludge blanket is equally spread over the upper liquid sludge surface.

Fig. 15 shows the situation during biogas release. The fast back flow of liquid sludge from the pres¬ sure equalisation tank 12 through the lower opening of the connection channel 11a into the methane fermenter 11 induces a convection roll, marked with the arrows in the drawing, supporting additionally the movement of the floating sludge blanket towards the floating sludge blanket removal channel 15.

Fig. 16 shows the compressed sludge blanket after biogas release (see also Fig. 7 and explanations). Now the sludge level in the methane fermenter 11 starts to slowly drop due to biogas accumulation at the top of the methane fermenter 11.

Fig. 17 shows the situation before normally biogas release (see also Fig. 10 and explanations).

Fig. 18 shows the floating sludge blanket removal from the methane fermenter 11 into the pressure equalisation tank 12 (see also Fig. 11 and explanations).

Fig. 19 shows the removed floating sludge blanket. It is now floating in the pressure equalisation tank 12, in which it is transported with the same transportation bars and changing sludge levels towards the outlet to overflow into the drainage and/or drying device 13.

Fig 20 shows the air flow caused by the strengthened chimney effect within the device according to the invention. The air is entering between the draining and/or drying device 13 and the preferably transparent cover 14. After heating up with solar thermal energy strengthened by the greenhouse

effect of the covered area and moving due to the slope of the cover towards the air inlet 14a, the air is then entering the tower between the sedimentation device 2a and 2b and the primary treatment de¬ vice 4. With an appropriate air stream device it can be used here to transport the floating sludge blankets of the sedimentation device 2a and 2b towards a blow off device (not shown). From here, it flows through the air inlet 4a to aerate the primary treatment device 4. It leaves the device according to the invention through the chimney on top of the primary treatment device.

List of devices:

device 1 : Inlet building with sand trap device 1a: Inlet pipe between inlet building 1 and inlet cylinder 2a 1 device 2a: Exemplary sedimentation device 1 (primary sludge) device 2a1 : Inlet cylinder of exemplary sedimentation device 1 2a device 2a2: Sludge blow off pipe of exemplary sedimentation device 1 2a device 2a3: Connection pipe between sludge blow off pipe 2a2 and hydrolysis and/or mixing tank 9 with valve. device 2b: Exemplary sedimentation device 2 (secondary bacterial sludge) device 2b1 Inlet cylinder of exemplary sedimentation device 22b device 2b2: Sludge blow off pipe of exemplary sedimentation device 22b device 2b3 Connection pipe between sludge blow off pipe 2b2 and hydrolysis and/or mixing tank 9 with valve. device 3 Pump sump for distributor 4b device 3a Pipe between pump sump 3 and distributor 4b device 4 Primary treatment device for waste water (purification up to full nitri¬ fication) device 4a: Air inlet device for device for waste water purification 4 device 4b: Waste water distributor of device for waste water purification 4 device 5: Gutter of device from primary treatment 4 device 5a: Connection pipe with valve between gutter 5 and pump sump 3 device 5b: Connection pipe with valve between gutter 5 and inlet building 1 device 5c: Connection pipe with valve between gutter 5 and inlet building 6 device 6: Inlet building for exemplary sedimentation device 22b device 6a: Inlet pipe between inlet building 6 and inlet cylinder 2b1 device 7: Gutters of sedimentation devices (2a nd 2b) device 7a: Gutter of sedimentation device 1 2a device 7b: Gutter of sedimentation device 2 2b device 7c: Connection pipe with valve between gutter 7b and secondary treat¬ ment 8 device 7d: Connection pipe with valve between gutter 7a and pump sump 3 for primary treatment 8 device 7e: Connection pipe with valve between gutter 7b and pump sump 3

for primary treatment 8 device 8: Secondary treatment (Denitrification and Phosphorus retaining de¬ vice) device 8a Outlet pipe for disposal or further treatment device 9 Hydrolysis and/or mixing tank. device 10 Connection pipe between hydrolysis and/or mixing tank 9 and methane fermenter 11 device 11: Methane fermenter device 11a: Connection channel between methane fermenter 11 and pressure equalisation tank 12 device 12: pressure equalisation tank device 13 Drainage and/or drying beds device 14 Covering device for drainage or drying beds 13 device 14a Air inlet device 15 Floating sludge blanket removal channel device 16 Floating sludge blanket transporting bars in the methane fermenter 11 device 17: Composting device