PROCEDURE FOR THE ENVIRONMENTALCOMPATIBLE TREATMENT OF SEWAGE SLUDGE AS WELL AS ARRANGEMENT COMPREHENSIVE A PURIFICATION PLANT

The available invention concerns a procedure for the environmentalcompatible treatment of sewage sludge, with which the sewage sludge in a putrid tower is stabilized using anaerobic microorganisms under at least predominant oxygen conclusion, as well as an arrangement comprehensively a purification plant with a putrid tower for the anaerobic stabilization of resulting sewage sludge.

Well-known purification plants have a mechanical stage with a sediment basin, in which sewage sludge sets off. Depending upon kind of the purification plant the sewage sludge consists of the removable materials in the waste water (primary mud) and the surplus sludge of the aeration basins and/or trickling filters. This mixture contains organic substance (approx. 60-80% of the Trockenschlamms) from the groups of materials of coal hydrates, fats and proteins. The sewage sludge is from there an ideal fertile soil for microorganisms.

One differentiates between aerobes and anaerobic microorganisms (bacteria). By the aerobes microorganisms “are breathed” the organic ingredients during a metabolic process to CO2 and H2O (oxidation). Anaerobic microorganisms cannot breathe however the high-molecular substances but “ferment” only (reduction). Mainly methane (CH4) and carbon dioxide (CO2) develop.

Since in the Rohschlamm microorganisms are contained in large number always, spontaneously anaerobic, micro-biological conversion processes begin in the matured Rohschlamm, which lead due to the hydrogen sulfide connections additionally developing thereby beside methane and carbon dioxide to smelling nuisances and in addition worsen the Entwässerbarkeit of the mud. For the removal of these critical characteristics rawdredge a so-called mud stabilization and afterwards a separation of the Schlammwassers one accomplishes.

By anaerobic stabilization one understands the biological dismantling of organic materials by anaerobic microorganisms. Hereunder applies according to DIN 4045 a mud as “stabilizes” if by an appropriate treatment at least one of the two principal purposes of mud stabilization, i.e. large decrease of the smell-forming ingredients and large decrease of the organic mud solids, were reached. Apart from these principal purposes are as secondary objectives still the improvement of the Entwässerbarkeit, the reduction of the pathogens and if necessary the production of energy desired.

Organic substance is stable, if it no more cannot be decomposed by mikrobiellen dismantling. Absolute stability can be achieved only by complete mineralizing, thus by burn or low temperature caronization. Biological dismantling processes run however iterated, approach thus an equilibrium on, without being able to ever reach it completely.

For practice a relative stabilization is sufficient, which is characterised by that no more bad smells are set free. The biological stabilization procedures are based on it, that to dismantling as controlled as possible to let run off fast and under avoidance of unpleasant emissions so to a large extent that the product can be afterwards only very slowly further decomposed. Sewage sludge of the local purification plants typically still consists of approx. 40-50% organic substances.

Compared with aerobes stabilization procedures offer anaerobic procedures different advantages. The power requirement for an oxygen supply escapes, it develops only little remaining bacterial substance, the dismantling effected in a closed container, the putrid tower, so that no smelling nuisance can occur, and which knows resulting sewer gas with a heat value of approximately 6000 kcal/m3 as valuable sources of energy is used.

Small and middle purification plants up to an order of magnitude of approx. 30,000 inhabitant mean d.c. values nevertheless use today mainly an aerobe stabilization. This is on the one hand because of that Investitionsund operating cost for the relatively small Blockheizkraftwerke does not pay for the generation of electricity of the resulting sewer gas. Since the energy from the sewer gas is not sufficient with such plants for the covering of the supply need, would have to be course-heated with fuel oil or natural gas, which would make the energy costs to increase and an enterprise unprofitable. On the other hand purification plants with anaerobic stabilization particularly do not order in the winter over sufficient own warmth from a generation of electricity of the existing sewer gas, in order to hold the micro-biological dismantling process at running, and must with fuel oil or natural gas zuheizen.

From there a more economical and at the same time pollution free procedure for the treatment of sewage sludge as well as an arrangement are to be indicated to task of the available invention for the execution of the procedure.

The task regarding the procedure solved by the characteristics of the requirement 1 and regarding the arrangement by the characteristics of the requirement 5.

With the procedure for the treatment of sewage sludge the sewage sludge in a putrid tower is stabilized using anaerobic microorganisms under at least predominant oxygen conclusion. Besides in a separate fermenter using anaerobic microorganisms from regenerating raw materials fermentation gas is produced and verstromt during a heat force process. The waste heat resulting with the heat force process is supplied thereby to the putrid tower according to invention by way of a thermal conduction for the support of anaerobic stabilization.

This procedure needs substantially less energy than at present in purification plants used aerobe procedure for the mud stabilization, with which mechanical mills or ultrasonic plants are used, with at least equivalent if not better result. The procedure according to invention done as far as possible without the use of fossil sources of energy and is substantially more pollution free from there. In addition develops less remainder mud, which would have to be deposited. Finally by the procedure according to invention still in an environmentally friendly manner produced river is made available.

Preferably in the putrid tower resulting sewer gas is supplied to the heat force process for generation of electricity. This makes possible a synergetic use for the same thermal engine both for the fermentation gas and for the sewer gas and thus a substantially more economical enterprise.

The waste heat resulting with the heat force process can favourably additionally for the thermal disintegration of the sewage sludge is used. Thus the micro-organic conversion is improved and the yield at sewer gas is increased.

Additionally the waste heat resulting with the heat force process can be used also for the drying process of the stabilized sewage sludge. This simplifies transport and Deponierung.

The arrangement according to invention covers a purification plant and a biological gas facility. The purification plant possesses a putrid tower for the anaerobic stabilization of resulting sewage sludge. The biological gas facility possesses a fermenter for the production of fermentation gas from regenerating raw materials as well as a thermal engine and a generator for the generation of electricity of the produced fermentation gas. Erfindungemäß is intended a thermal conduction from the thermal engine to the putrid tower, by which resulting waste heat the putrid tower is supplyable for the support of anaerobic stabilization.

Preferably in addition a gas line is by the putrid tower of the purification plant to the thermal engine of the biological gas facility is intended, by which in the putrid tower resulting sewer gas of the thermal engine is supplyable for generation of electricity.

Appropriately a gas meter is intended in the gas line. This permits an economically independent enterprise of the two plants and permits a separate account of the produced and used up energy quantities. In addition an statement of the produced energy quantities makes possible also an optimization of the processes running off.

Favourably also still another device for the thermal disintegration of the sewage sludge and/or a device can be intended for the drying process of the stabilized sewage sludge in the purification plant, which are supplied via a thermal conduction with waste heat of the thermal engine.

In the following a remark example of the invention is more near described on the basis the designs. Show:

Figure 1

a block diagram of the arrangement according to invention and

Figure 2

a more detailed block diagram of the biological gas facility.

In figure 1 is represented in a block diagram, as a biological gas facility 20 and the putrid tower 11 of a purification plant cooperate. In the biological gas facility regenerating raw materials become 12, so-called Nawaros, in a Gärprozeß under formation of fermentation gas fermented that then in a Blockheizkraftwerk one verstromt. The biological gas facility 20 produces thus river 14 and warmth. A part of the warmth is needed in the biological gas facility 20. The largest part of the warmth is available however as waste heat, which is led over a thermal conduction 13, for example a warm water line, for the heating up of sewage sludge into the putrid tower 11. Remaining fermenting remainders of 16 from the biological gas facility 20 can be used as fertilizers.

In the putrid tower 11 by microorganisms is putrefied to sewage sludge during an anaerobic process, whereby sewer gas develops. The sewer gas is supplied to the Blockheizkraftwerk of the biological gas facility 20 by way of a gas line 15 with gas meter 15 ' and gas processing stage 15 ''. Of course the sewer gas can be used alternatively also in its own Blockheizkraftwerk in the purification plant.

Ausgefaulter sewage sludge 17 is transported to a drying unit 18, which is likewise operated over a thermal conduction 13 ' with waste heat from the biological gas facility 20. The finished dried sewage sludge 19 is then supplied to a dump. An optional, additional plant for thermal disintegration 11 ' of the sewage sludge 17 expenditure-putrefied and a thermal conduction 13 '' are broken shown.

The function mode of the biological gas facility 20 is more near shown in figure 2. Heart of the biological gas facility is a fermenter 21, which is a reactor, in which from biological material in damp atmosphere under Luftabschluß from multi-level mikrobielle degradative reactions so-called fermentation gas results. Fermentation gas consists to approximately 50 to 70% of methane (CH4) and to approximately 30 to 50% of carbon dioxide (CO2). Other gas components such as oxygen, nitrogen, ammonia, hydrogen, Carbon monoxide and Schwefelwasserstoff are contained only in small concentrations in the fermentation gas and make in sum usually less than 1 VOL. - % of the resulting mass of gas out. As biological material for the fermentation here Nawaros are used like e.g. corn, grass, rape, or green wastes.

Delivered biological material 12 is cleaned by foreign matter and cut up in a Häcksler 27. Then it arrives to the biological gas facility 20 into an assumption shelter (not shown). Conveyors transport the bio property into a Dosierer 28, into which it with zückgeführtem process water as well as already vergorenem material one mixes. This “inoculation material” accelerates the Gärprozeß. A pump carries the moistened biological material into the fermenter 21.

Over approx. 2 weeks the bio property flows through the fermenter 21. The fermentation gas developing with the Gärprozeß is cleaned, dehumidified collected, in a gas processing stage 25 and led without intermediate storage across a gas line 25 ' into the Blockheizkraftwerk 22, which contains a thermal engine like here a gas engine 23 and one with this coupled generator 24. Beside the fermentation gas from the fermenter 21 also the likewise methanhaltige sewer gas from the putrid tower 11 of the purification plant is supplied to the gas engine 23 by way of a gas line 15 with gas processing stage 15 '' and gas meter 15 ' for burn.

About well a third of the energy from the burn of the fermentation gas is converted in the Blockheizkraftwerk 22 into electricity. Scarcely two thirds of the energy are available against it only in the form of heat energy. A part of the heat energy is needed, in order to heat over the warm water line 26 the fermenter 21 on process temperature from for instance 55°C to. Additionally the fresh biological material before filling in can be preheated still over a heat exchanger (not shown).

The largest part of the warmth is available as waste heat. While the waste heat is usually transferred with conventional biological gas facilities for lack of customers unused to the ambient air, the invention uses the waste heat for the support of the anaerobic stabilization of sewage sludge in the purification plant. The river 14 produced over the power consumption of the biological gas facility 20 outside into the public electricity net one feeds.

From the fermenter 21 the fermenting off remainder is removed and drained by means of Austragsund Preßschnecke 29. A part of the Preßwassers will for the humidification of the new biological material in the Dosierer 28 needed, the remainder of the Preßwassers 29 ' can either in the agriculture as fertilizers be used or, since no environmentalharmful material in the biological gas facility is used, directly the purification plant be supplied.

The dry fermenting remainder of 16 is carried into a Nachrottebunker (not shown), where it kompostiert under effect of atmospheric oxygen, before it is used as in demand fertilizers in the agriculture.

The dimensioning of the biological gas facility 20 (e.g. 250 KW, 500kW or 1000kW) takes place according to the need of the purification plant. Mainly the waste heat serves the biological gas facility 20 for the thermophilen enterprise of anaerobic stabilization running off in the putrid tower 11 in particular during the winter months. However the waste heat can be used not only the heating of the putrid tower 11, but be made usable besides also in other way the optimization of the function of the purification plant. On the one hand the waste heat can be used as in the remark example also favourably for the drying process of the sewage sludge expenditure-putrefied. On the other side a thermal disintegration of the sewage sludge can be suggested with approx. 70-80°C with the waste heat, like in figure 1 broken, be accomplished in a subsequent treatment step.

Then, the pumpable and sufficiently homogenized sewage sludge already preheated goes through a thermal disintegration plant 11 after the fermentation in the putrid tower 11 '.

During mesophilen putrefying in the putrid tower 11 70 to 80% of the usual sewer gas yield is already set free. By a further putrefying only relatively little gas yield would let itself obtain without the thermal treatment in the plant 11 ' , in relation to the container volume necessary for it.

Via thermal disintegration with 70-80°C a cell explanation of the mesophilen bacteria trunks from first putrefying and due to the destruction of the still existing disease germs and Unkrautsamen takes place again organic material is set free. In addition the cell structure of with difficulty degradable is destroyed and otherwise, in justifiable periods not for the dismantling process of available materials. These are unlocked, hydrolyzed and made possible so their further fermentation also with short retention times. The heating is made directly by a hot water line 13 '' with the waste heat of the Blockheizkraftwerkes 22 (approx. 90°C hot water). Subsequently, the disintegrated sewage sludge is led into a Nachfaulreaktor of the plant 11 ', where it is continued to decompose during a second putrid process.