CA2263668A1 - Bioreactor - Google Patents

Abstract

In a bioreactor (8) for conditioning water loaded with organic substances, in particular from car washing installations, the reactor container has a solid bed (48) made of a porous substrate material capable of adsorbing the organic substances contained in the waste water and sown with micro-organisms known per se which degrade the organic substances contained in the water. The solid bed (48) is located on a permeable substrate (47) and a water collecting chamber (46) is provided below the solid bed, upstream of the outlet for the treated water. The outlet (26) is at the same time designed as a backwashing inlet. An inlet (24) and a backwashing outlet (28) are provided above the solid bed (48).

Description

Datei:l~.\t~ U' -~
A bioreactor Description This invention relates to a bioreactor for treating water loaded with organic substances, in particular from car washes, the reactor vessel having a fixed bed con-sisting of a porous supporting material capable of adsorbing the organic ingredients of the wastewater and colonized with microorg~ni.cm.c known in the art which de-grade said organic ingredients of the water.
It is known to treat washing wastewaters from car washes before passing them into the municipal sewerage by applying drainage systems according to DIN 1986 and DIN 1999 so that they meet the demands of the legislator and local govern-ments. Washing wastewaters from car washes are accordingly purified mechanicallyin a silt chamber, largely freed from mineral oil hydrocarbons in a light liquid sepa-rator, collected in a reservoir and passed into the sewer system via an inspection chamber. Further steps, such as chemical and/or biological tre~hnent can be in-cluded in washing wastewater purification and serve to reduce the need for freshwater.
According to DE-A-26 51 483 one purifies car wash wastewater cont~ining biodegradable cleaning and preservative agents as well as solids by mixing the wastewater with a polymeric flocculant and passing it first through a sedimentation zone with reduced water flow and then via an adsorbent.
DE-C-41 16 082 describes a method for water tre~tment in car washes wherein the arising washing wastewaters are purified mechanically or mechanically and bio-logically and recycled into the car wash. The solids arising during mechanical purifi-cation are collected into special-disposal garbage batches. The pollutants are treated mechanically or biologically in a multistage process in this method in such a way that solids with hydrocarbons and pollutants are separated from the car wash waste-water by settling and collected in a first circuit, the hydrocarbons and pollutants with wastewater cont~ining washing substances are extracted from the washing zone during collection, and the mechanically clarified wastewater is freed from nonde-gradable fractions by flotation and by biological reaction in a second circuit.

The common disadvantage of known methods is that washing wa~l~w~le must be treated in elaborate multistage processes. The arising solids, generallyflotage and sand and silt washed offthe vehicles, must be disposed of as garbagebatches requiring special treatment. Water and solids collecting in the plant have a smell which can assume an extreme and annoying degree. Reuse of purified washingwastewaters requires a high proportion of fresh water. The arising surplus water is to be fed to municipal wastewater treatment via a sewage connection. It has turned out that these inadequacies are mainly due to ineffective biological clarification of washing wastewaters.
The invention is thus based on the problem of increasing the efficiency of bio-logical treatment of washing wastewater for complete reuse. It must be possible to resume treatment without any problem after times of low washing activity. This is to be done by providing an effectively working bioreactor tailored to the requirements in treatment plants of car washes.
This problem is solved by a bioreactor of the abovementioned type wherein the fixed bed is located on a permeable support, a water collecting chamber is provided below the fixed bed upstream of the outlet for treated water, the outlet being at the same time formed as a backwash inlet, and an inlet and a backwash outlet are pro-vided above the fixed bed.
Preferred embodiments are the subject of the subclaims.
The inventive bioreactor is filled with a fixed-bed m~teri~l which is suitable for adsorbing mineral oil hydrocarbons and car polishes while also having a porosityand surface which promote the colonization of microorgani~m~. These colonizing zones are necessary so that the forming bacteria lawns are not torn off by the shear forces of the flowing water and discharged from the system.
Below the fixed bed there is a water collecting chamber separated from the fixed bed by a permeable support, e.g. screen gauze, so that the fixed-bed material is not discharged from the working zone. Water is pumped out of this water collecting chamber either sideways through the vessel wall or upwards through a specially provided pipe. The inlet and outlet are formed by inlet and outlet manifolds so as to obtain uniform water dist,ribution and uniform flow behavior both in normal opera-tion and during backwashing.
During backwashing of the bioreactor, which must be washed free from time to time, suspended matter and surplus microorg~ni~m~ are removed from the reactor vessel to m~int~in permeability. Backwashing is done in counle~ enl from the bottom to the top via a specially designed elutriation and overflow device. Thiselutriation and overflow device has an upwardly tapering cross section, which leads to a constriction of the free reactor cross section and entails a higher flow rate of the backwash stream. The higher flow rate of the backwash stream is suitable for com-pletely removing floating suspended matter from the inlet area.
Incorporated measuring probes for detecting the levels for flow control and run-dry protection of the pumps are integrated into the total system of the treatment plant in terms of control technology and allow the necessary adaptation to t,he differ-ent operating conditions at washing times, ensuring in particular regular backwash-ing and an automatic night run as well as automat,ic refeeding of fresh water.
The inventive bioreactor is used in a method which has a mechanical and a biologically working treatment step. The mechanical treatment step consists of the silt chamber in which entrained coarse dirt is sedimented. This generally involves mineral particles which are frequently polluted by mineral oil products. Coarsermineral oil particles, for example from the waxing or undercoat,ing of a motor vehi-cle, also pass into the silt chamber.
Biological treatment of the silt load also occurs in the silt chamber to a relevant extent. The backwash of the filtering installation and the bioreactor as described be-low causes oil-degrading microorg~ni~m~ to pass repeatedly into the silt chamber, colonize t,here and do their work. A large part of the organic load of t,he silt chamber is thus decomposed by microorg~ni~m~. Experience has shown t,hat t,he content ofthe silt chamber is decomposed after a few months into a hllmllslike mass which is no longer co~ ted with mineral-oil components and can readily be disposed of with household garbage.

After running through the silt chamber the wastewater passes into a reservoir serving substantially as a buffer, out of which water is continuously pumped into the inventive bioreactor via a filtering installation. The buffer effect of the reservoir has two aspects, firstly a quanlilalive one since a continuous wa~l~water stream must be fed to the bioreactor regardless of the frequency of use of the car wash. Secondly the reservoir serves as a dilution tank for high-concentration dirt loads arising in clean-ing especially dirty motor vehicles or ones co~ ted with special polhlt~nt~.The filtering installation is a conventional filter for removing the suspended-matter load and consists for example of several altern~tin& layers of coarse and fine sand beds. The aerosol filter can be passed by wastewater with or against gravity and must occasionally be backwashed with clean water for cleaning or else replaced. The filling of the aerosol filter is expediendy carried on perforated plates or the like un-der which the outlet is located.
The inventive bioreactor downstream of the aerosol filter is passed by waste-water with gravity and harbors on its supporting material the microorg~ni~m~ which degrade the dirt load in the wastewater arising in a car wash. These are generally aerobically working bacteria which are known in the art and can be obtained withselection mech~ni~m~ likewise known.
The clean water emerging from the bioreactor is then collected in a clean-water tank and fed from there to the car wash for reuse.
Obviously one must react to the constant loss of recycle water due to evapora-tion and drag-out via washed motor vehicles by feeding in clean water. It has been shown in a pilot plant that several tens of thousands of cycles can readily be achieved with wastewater thus treated and supplemented.
The bioreactor consists of a fixed bed of a porous supporting m~tçri~l which can adsorb the organic ingredients of the wastewater and offers the required micro-org~nism~ sufficient support for colonization. The microorg~ni~ms form on the sur-face of the supporting material and in the pores a lawn which filters the wastewater flowing past and takes in the dirt/nutrients contained therein. The adsorptive effect of the supporting material promotes this effect by feeding the components adsorbed from the wastewater to the microorg~ni~m~.
To ensure sufficient permeability of the fixed bed for the washing water, the porous supporting material expediently exists in the form of a packed bed which of-fers room between the individual support particles in addition to the actual pore space. Suitable porous supporting materials are for example coal, clay, silica gel or zeolites in pelletized form or else plastic foam flakes with a sufficient pore volume, for example of polyurethane, polystyrene or the like. An especially suitable material has for example a particle size of 1 to 10 mm, a vibration density of 0.25 to 1.0 g/cm3, a pore volume of 0.40 to 1.0 cm3/g and a surface of more than 500 m2/g.
However, other materials with comparable physical properties can likewise be used.
Obviously the bioreactor must be regularly backwashed to avoid being clogged with suspended particles or blocked by excessive bacterial growth. The bioreactor is backwashed in such a way that the washed-out materials are carried back into the silt chamber where the washed-in oil-degrading bacteria can do their work.
It is expedient to keep the bioreactor in service in times of low washing fre-quency via a so-called night run. For this purpose one expediently recycles clean water into the reservoir and passes it from there into the bioreactor via the aerosol filter. The circuit ensures regular flow through the bioreactor and thus also a regular nutrient supply from the reservoir. One ~iml~lt~neously permits the dirt load con-tained in the reservoir to be degraded slowly ovçrnight which means that the newwa~l~waler inflow on the next day is first diluted with relatively clean reservoir wa-ter, thereby avoiding a sudden shock load on the microorg~nism~.
As mentioned above, the bioreactor is run aerobically. The quantity of oxygen contained in the washing water is generally insufficient for this. It is therefore expe-dient to introduce oxygen or air into the bioreactor, expediently via an air injector.
One branches off part of the water rurming out of the bioreactor, saturates it with air and recycles it into the bioreactor. However, it is also readily possible to recycle water into the bioreactor from a clean-water tank after it has been saturated with air.

A clean-water tank collects the clean water running out of the bioreactor, m~king it available for reuse in the washing cycle. A sufficient volume ensures that enough water is available both for cleaning purposes and for the tre~trnent method (backwash, arle,lull). The clean water released to the car wash can first be sterilized via a degerming facility, for example with the help of UV radiation.
Obviously the preservative agents used in the washing process have no bio-static or biocidal components and are completely biodegradable. The rate of biode-gradation is to be considered in dimensioning the tre~nent plant, the faster degrad-ability is, the smaller the reservoir, bioreactor and clean-water tank can be designed, within certain limits. It has turned out that for an average car wash the silt chamber and reservoir and the clean-water tank should have a collecting volume of 6 m3 and the filter unit and bioreactor a capacity of 1 to 1.5 m3. Materials that can be used for all pipes and tanks may be either corrosion-resistant metals or plastics that meet the requirements, in particular glass fiber-reinforced plastic or HP-PE.
Washing wastewater arising in a car wash is thus generally fed via a silt cham-ber known in the art to a reservoir and from there via an aerosol filter to an aerobi-cally run bioreactor. The supporting material of the fixed bed is porous, has a large specific surface, can adsorb water ingredients and is used for colonization of special microorg~ni~m~. Water in the reactor is constantly circulated by a circulating pump and enriched with oxygen, preferably atmospheric oxygen from the ambient atmos-phere, without pressure by a suitable device, preferably an injector. The circulation rate can be varied within wide limits. It should be such that the biofilms are not damaged. Washing wa~l~wale~ passes from the bioreactor via an overflow control into a clean-water tank. From there it is recycled 100% to the washing process, op-tionally via a degerming facility.
It is necessary to backwash the bioreactor when the pressure difference be-tween inlet and outlet of the aerosol filter or the reactor vessel reaches a limiting value as a measure for the load of retained suspended matter or surplus biology, for example 0.5 bars.

It has further turned out that the inventive bioreactor is suitable for taking up and treating co~ ted water from the workshop area and gasoline pump area of a gasoline station. It is therefore understood that not only the wastewater arising in the car wash but also such further wastewater can be used. The inventive bioreactor is thus suitable for replacing the plants for treating atmospheric water as required for gasoline stations. The inventive reactor can also be used advantageously in other ways.
By reason of its load in particular through the content of wa~l~w~ter, one regularly selects for the reactor vessel according to the optimal vessel formation for such static loads in tank and apparatus construction a cylinder with a plerelably vaulted bottom and cover and consisting of metal sheets in weldments. However, such vessels are not optimal for many applications of the inventive bioreactor and for example for wastewater treatment plants of car washes. In these and other cases of application of the invention, the reactor vessel and optionally the subassemblies of the treatment plant cooperating therewith must be accommodated in a closed room, which preferably in car washes is optimally disposed directly beside the washing installation. By reason of the restricted room heights one obtains, for the accruing quantities of wastewater, cylinder diameters which are larger than usual doorways, the latter being a constructional given. Since the usual cylindrical vessels do not fit through such doorways, one regularly proceeds in practice in such cases by breaking a sufficiently large assembly opening in one of the walls of the room for the reactor vessel to fit through; after it is installed the wall opening must be closed again. The entailed expenses and the necessarily resulting danger to the statics of the installation building are an extreme disadvantage.
According to the invention this is remedied and a more favorable solution pro-vided for the treatment plants with a bioreactor which can be used for all wastewater capacities. According to the basic idea of the invention as rendered in claim 12, the horizontal projection of the reactor vessel keeps to the constructional givens within a given areal ~limen~ion, thus corresponding in the stated example to the usually stan-dardized doorway of the installation room which can be used as a filnd~ment~l quantity in the inventive vessel horizontal projection. Since the room hei~ht~ are normally also given constructionally and on the other hand by the wastewater ca-pacity of the tre~tment plant itself, this yields the other areal dimension of the reac-tor vessel and thus a reactor vessel forming the module of a modular system which manages the wastewater volume of a specific wastewater treatment plant with one or more modules, i.e. parallel-connected vessels.
The invention therefore has the advantage of giving the builder extensive free-dom of design in choosing the building and in particular in choosing the areal di-mension of the installation of the treat-nent plant, and not nececsit~tin~ y final or temporary changes in the building to adapt to the assembly and installation of the reactor vessels.
It has turned out in practice that embodiments of the invention according to claim 13 are best suited for the design of the reactor vessel in order to meet the con-structional requirements. Taking as a basis the standardized 80 cm doorway, one normally obtains an almost square quadr~n~ r horizontal projection, although other horizontal projection shapes are of course also possible for ~ltili7ing the advan-tages of the invention. In the assumed case, the shorter side of the rectangle is the constructionally given areal dimension of the vessel horizontal projection.
Apart from constructional specifications, the vessel specifications resulting from the load of the reactor vessel can also be fulfilled with vessel shapes not corre-sponding to the customary cylindrical shape. This is rendered in claim 14. It has sur-prisingly tumed out that a vessel made of thermoplastic resin has sufficient inherent rigidity by reason of its welded structure of flat plates to be able to remove the pri-marily static loads of the vessel filling, in particular with wastewater, substantially without deformation. This is achieved in particular by so-called HP-PE plastics,which are the subject of claim 15.
The flat walls and flat bottom of such a vessel also have another advantage.
The number of vessels resulting from the modular system can be installed wall bywall in space-saving fashion. This holds even if only one module is used for such a plant because the polygonal horizontal projection can be accommodated better within given ground plans of buildings than the usual circular cross section of ves-sels. The wall-by-wall arrangement of several modules therefore utilizes the avail-able space offer in usual ground plans of rooms optimally, in particular if the vessel horizontal projection is rectangular to square. It is then recommçn(l~kle, however, to make use of the features of claim 16, since they enforce the opli~ association of several modules of the modular system with a base frame.
The invention will be explained in more detail by the following figures, in which:
Fig. 1 shows schematically an embodiment of the inventive bioreactor, Fig. 2 shows the integration of the inventive bioreactor according to Fig. 1 into a total plant for wastewater treatment, Fig. 3 shows details of a preferred embodiment of the backwash outlet of the inventive bioreactor, Fig. 4 shows a schem~fic perspective view of the installation of two modules, and Fig. 5 shows a section along line V-V of Fig. 4.
The bioreactor according to Fig. 1 consists of reactor vessel 8 which is in turndivided into three colllp~llllents, lower water collecting chamber 46, fixed bed 48 and upper inlet chamber 49. Between lower water collecting chamber 46 and fixed bed 48 there is permeable support 47, for example of screen gauze or a perforated plate, which reliably prevents penetration of the fixed-bed filling. Upper inlet cham-ber 49 must be delimited from fixed bed 48 only if the fixed-bed filling consists of a material with low specific weight which floats up in the backwash stream under nor-mal conditions. In this case, a water-permeable membrane can also be inserted there.
Water to be treated passes via pipes 27 and 29 to distributing manifold 24 into upper inlet chamber 49. After passing through fixed bed 48 it is discharged fromlower water collecting chamber 46 via the outlet manifold and pipe 30 by means of pump 31. Clean water from pipe 30 is mixed with air via pipe 32 and injector 10 before passing on through valve 35 into a clean-water tank.

Part of the water from pipe 30, after it has been enriched with air via injector10, is recycled via valve 34 and pipe 33 into pipe 29 and bioreactor 8 in order to meet the oxygen ~lem~n~ of the microorg~ni~m~ there.
The pipe pressure within the system is constantly monitored; pressure measur-ing point 40 dele~ illes the pressure in pipe 30 and is used for calculating the differ-ential pressure between inlet and outlet of bioreactor 8. Upon a drop of pressure in pipe 30 over the inlet pressure, which indicates clogging of the fixed bed, the back-wash system is activated whereby clean water is pressed into outlet pipe 30 via pipe 17 after opening and closing of the corresponding valves, thereby reversing the di-rection of flow. Clean water passes through manifold 26 into the lower collecting chamber and presses from below through fixed bed 48 into upper distributing cham-ber 49 from where it is passed via overflow 28 and pipe 14 into a silt chamber. Inlet 27 or 29 via manifold 24 is closed in this case.
Level control 25 with different measuring points is used for monilolillg the water level in bioreactor 8, being connected via control line S with pump 31 and a control center. In normal operation the water level is constantly held between the two measuring points in upper inlet chamber 49. A further measuring point in lower collecting chamber 46 is required if fixed bed 48 is run dry for m~int~n~nce or for other reasons.
Fig. 2 shows the total method. The same numerals designate the same posi-tions. The dotted lines designate control lines for operating the plant.
Wastewater from the car wash, a workshop or the surface runoff water of a gasoline station area passes via feed pipe 1 into silt chamber 2 where coarse dirt is se~imented. Pipe 21 continues into reservoir 3 which serves as a buffer for wastewa-ter freed from coarse dirt. Reservoir 3 contains level control 4 with an upper and a lower switching point.
Water from reservoir 3 is passed via suction body 5 and feed pump 6, which form one unit in the present embodiment, through pipe 22 into aerosol filter 7. Pipe 23 protected by a valve pertnits sampling of dirty water from pipe 22.

Water passes from reservoir 3 into aerosol filter 7 via distributing manifold 24.
The filter is filled with alt~rn~ting layers of coarser and finer sand through which wastewater runs from top to bottom. Via manifold 26 filtered wastewater is carried away through pipe 27 using pump 9. Level control 25 prevents the filter device from running dry but also has a lower switching point for emptying the filter device more or less completely. Overflow 28 recycles via pipe 14 into silt chamber 2, being re-quired when filter 7 is backwashed.
Water removed from the filter via manifold 26 passes via pipe 27 and pump 9 as well as pipe 29 into bioreactor 8. There it is distributed by manifold 24 over the surface of the porous supporting material located therein, expediently active carbon pellets with large pore volume and sufficient empty space between the individualparticles. The porous supporting material is colonized with microorg~ni~m~ condi-tioned to the organic dirt load of the wastewater. Wa~l~w~lel runs through the fixed bed of the bioreactor from top to bottom and is fed to clean-water tank 11 via mani-fold 26 of bioreactor 8 via pipe 30 using pump 31. Level control 25 ensures suffi-cient filling of bioreactor 8, as with aerosol filter 7.
An injector inserted in pipe 30 injects air taken in via pipe 32 into the water removed from bioreactor 8. Water saturated with air is fed via pipe 30 firstly to clean-water tank 11 but partially also recycled via pipe 33 into the bioreactor, where it ensures a sufficient oxygen supply for the reactor and the microorg~ni~m~. Sole-noid valves 34 and 35 ensure the right distribution ratio of air-saturated water be-tween bioreactor 8 and clean-water tank 11. Batchwise operation of bioreactor 8 is likewise possible, however, whereby a circuit through pipe 33 performs the air sup-ply. Only completely clarified water is fed to tank 11.
Clean-water tank 11 receives the biologically clarified water from bioreactor 8.Level control 36 ensures that the clean-water tank is filled with a sufficient quantity of water to permit both washing operation and night circuit operation to be main-tained. If the quantity of circulating water is too small, fresh water can be supplied via pipe 12.

Water is removed from clean-water tank 11 via pipe 37 using pump 15 and fed to pipe 13 into the car wash. Degerming facility 18, preferably based on UV radia-tion to avoid addition of bactericidal degerming agents, ensures the sterility of the washing water. Buffer vessel 19 filled with air ensures, in conjunction with pump 15, a uniform water flow into the car wash downstream. Pressure meter 39 is usedfor monitoring and controlling the pressure.
Outflow 38 leads alternatively into the sewerage and serves to remove surplus water in times of above-average water accllmlll~tion. This is expedient in particular when the treatment plant also treats surface water from a gasoline station area and is subject to large quantities of water from heavy precipitation. Otherwise the plant works in 100% circuit operation.
Further pressure measuring points are located in pipes 27 to the bioreactor and 30 to the clean-water tank and bear reference signs 40. They are used for monitoring the working pressure of pumps 9 and 10.
In case one of these vessels is largely clogged with dirt particles or biomass, a backwash process is commenced from clean-water tank 11 via pipes 37, pump 15 and pipes 16 and 17 into aerosol filter 7 and bioreactor 8. Water enters the reactors via lower manifold 26 and washes the dirt particles or biomass via overflow 28 and pipe 14 into silt chamber 2. In this way microor~ani~m~ also pass into silt chamber 2 and can colonize it and effect biological treatment of the se~imente~ dirt there.
In times of low washing activity, i.e. in particular at night, on weekends and holidays, water circulation is preferably kept up in order to keep the aerosol filter and bioreactor in service. This circulation begins in clean-water tank 11 and runs via pipe 37, pump 15 and pipe 43 back into reservoir 3. Solenoid valve 44 is therebyopened via the central control device. Stop valves 41 and 42 to the washing installa-tion and into the backwash pipes are sim~lltaneously blocked. The circulation then extends, as in normal treatment operation, from reservoir 3 via aerosol filter 7 and bioreactor 8 into the clean-water tank. After a certain time of circulation the quality of water in circulation and in the connected tanks gradually approaches the quality of water in clean-water tank 11.

Fig. 3 shows a special embodiment of inventive bioreactor 8 with respect to its overflow 28. In the case of backwashing, backwash water is passed from a clean-water tank via pipe 30 into lower collecting chamber 46. From collecting chamber46 it passes through screen gauze 47 into fixed bed 48, flushes the latter and washes residues and loosely a&ering microorg~nisms into upper chamber 49. Backwash water is discharged via overflow 28 which is saucer-shaped - or funnel-shaped - and opens into outlet pipe 14. The saucer- or funnel-shaped formation of overflow 28with an upwardly tapering cross section leads to an acceleration of water flow on the way upward so that the broken-away particles are accelerated and guided over theedge of overflow 28 into the saucer and from there into pipe 14. The backwash stream therefore extends relatively uniformly in the area of the fixed bed and di-rectly above, accelerating only in the upper area so that the dirt particles can be transported specifically into the overflow.
As results from the view of Fig. 4, a given trea~nent plant requires two reactorvessels 50 and 51 for bioreactor 8. Vessels 50 and 51 are identical in their design and their capacity. Each of the vessels corresponds to the module of a modular sys-tem which corresponds to the constructionally given capacity of the treatment plant through multiplication of the modules. Since the horizontal projection of reactor ves-sel 8 consists of the horizontal projections of the two modules 50 and 51 it corre-sponds to twice the horizontal projection of the two modules whose contours are formed by shorter sides 52, 53 and longer sides 54, 56 of the rectangle. The length of shorter sides 52, 53 corresponds in the embodiment to a constructional given result-ing for example from a standardized 80 cm doorway through which the two modules would have to fit if installed in a room whose access is dele~ ed by the doorway.
The further areal (limen~ions are given by equally long sides 54, 56 of the rectangle which result from the desired vessel volume with consideration of vessel height H.
The vessel height is therefore normally likewise given by the assembly and/or the room height. Multiplication of vessels 50 and 51 then results in the constructionally given capacity of the treatment plant. While the vessel horizontal projection is given by constructionally given dimension L, vessel ~limen~ion I at right angles thereto can be selected for the module.
In this way one can manage any capacity of the treatment plant with modules 50and51.
The vessel has flat rising walls 57 to 60 and a flat bottom not indicated by Figs.
4 and 5. Rising walls 57 and 58 partly shown in Fig. 5 are made of thermoplasticresin in the form of equally thick plates 61 and 61. These plates are interconnected in material-locking fashion at their m~ lly associated edges at 63 with a welding joint disposed at 64. These material-locking connections together with the suffi-ciently ~limen~ioned plate thickness result in a ~limen~ionally stable vessel able to remove the loads to be received almost without deformation. A thermoplastic resin that can be used is a so-called high-pressure polyethylene.
For holding modules 50 and 51 together and mounting them correctly, base frame 65 composed in bending-resistant fashion of metal sections 65 is provided.The frame members, some of which are shown at 66 to 68, can likewise be assem-bled into a frame construction in bending-resistant fashion in the corners by mate-rial-locking connections, in particular weldings.

Claims (17)

Claims

1. A bioreactor for treating water loaded with organic substances, in particularfrom car washes, wherein the reactor vessel has a fixed bed consisting of a porous supporting material capable of adsorbing the organic ingredients of the wastewater and colonized with microorganisms known in the art which degrade the organic ingredients of the water, characterized in that the fixed bed (48) is located on a permeable support (47), a water collecting chamber (46) is provided below the fixed bed upstream of the outlet (26) for treated water, the outlet (26) being at the same time formed as a backwash inlet, and an inlet (24) and a backwash outlet (28) are provided above the fixed bed (48).

2. The bioreactor of claim 1, characterized in that the permeable support (47) consists of screen gauze.

3. The bioreactor of claim 1 or 2, characterized by a return pipe (19) with an inserted air injector (10) for recycling clean water saturated with air into thebioreactor (8).

4. The bioreactor of any of the above claims, characterized in that the inlet (24) and/or the outlet (26) are formed as distributing manifolds.

5. The bioreactor of any of the above claims, characterized by a run-dry protection in the bioreactor (8).

6. The bioreactor of claim 5, characterized by a level control controlled via control lines (S) and having switching points for the minimum and maximum water levels in accordance with the particular operating condition.

7. The bioreactor of any of the above claims, characterized in that the backwash outlet (28) is formed as an overflow disposed in the middle of the bioreactor (8) and tapering upward.

8. The bioreactor of any of the above claims, characterized in that the porous supporting material is present as bulk material.

9. The bioreactor of claim 8, characterized in that the porous supporting material consists of coal, clay, silica gel or zeolites in pelletized form or of plastic foam flakes.

10. The bioreactor of any of the above claims, characterized in that the porous supporting material consists of activated carbon or foamed clay with a grain size of 1 to 10 mm, a density of 0.40 to 1.0 cm3/g and a surface ~ 500 m2.

11. The bioreactor of any of the above claims, characterized by pressure measuring units (40) downstream of the bioreactor (8).

12. The bioreactor of one or more of the previous claims, characterized by a horizontal projection of the reactor vessel (8) which is constructionally given in one areal dimension (52, 53), the other areal dimensions (54, 56) of its horizontal projection being adapted with consideration of the vessel height (H) to a vessel volume which corresponds to the module (50, 51) of a modular system corresponding to a constructionally given capacity of the treatment plant through multiplication of the vessels (50, 51).

13. The bioreactor of one or more of the previous claims, characterized in that the vessel horizontal projection is rectangular to square, the constructionally given areal dimension (2) being determined by the length of one of the two pairs of parallel sides (52, 53; 54, 56).

14. The bioreactor of one or more of the previous claims, characterized in that the vessel has flat rising walls (57 to 60) and a flat bottom which are made of a thermoplastic resin and interconnected in material-locking fashion, for example welded, at their mutually associated edges (63).

15. The bioreactor of one or more of the previous claims, characterized in that the thermoplastic resin used is a high-pressure polyethylene (HP-PE).

16. The bioreactor of one or more of the previous claims, characterized in that a common base frame is provided for holding several vessels of the modular system together.

17. The bioreactor of one or more of the previous claims, characterized in that the constructionally given areal dimension is the width of a 80 cm doorway forming the access to an installation room of the treatment plant.