GB2029391A

GB2029391A - Biochemical Thermophilic Waster Water Treatment

Info

Publication number: GB2029391A
Application number: GB7903839A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-04-10
Filing date: 1979-02-02
Publication date: 1980-03-19
Also published as: GB2029391B; DE2815507A1

Abstract

Finely dispersed waste water is conducted through a heated microorganism treatment zone at from 37 to 72 DEG C while air or oxygen or oxygen-enriched air is supplied to the treatment zone in addition to oxygen dissolved in the waste water. A treatment tank 1 holds filler material 8 onto which is fed waste water from a distributor 4. After trickling over the filler material the treated water is withdrawn from discharge pipe 10 into collecting basin 11, from which it is discharged or recycled to the distributor 4. Air withdrawn through the discharge pipe 10 is replaced by air passing through pipe inlets 14. Heating elements 15 and 16 maintain the temperature of the treatment zone. <IMAGE>

Description

SPECIFICATION Biochemical Thermophilic Waste Water Treatment This invention relates to biochemical aerobic thermophilic waste water treatment Aerobic thermophilic waste water treatment requires the ample supply of oxygen to the active microorganisms. The oxygen supply is limited by the absorption of oxygen in water with rising temperatures. As the thermophilic treatment operates at temperatures of 310 to 345 K the aeration has to be intensive or extended. Intensive aeration is known to cause excessive foaming which limits the practicability of this method.

Extended retention time on the other hand requires larger tank volumes.

A method of waste water treatment by thermophilic bacteria also called liquid decomposition is known as a specialty of the activated sludge process. This method requires extended retention time due to the high pollutant load and the iow solubility of oxygen in hot water.

This method brings about high operating and investment costs on account of the extended retention time. The excessive foaming which is to be observed with all types of aeration also is a serious draw back to thermophilic treatment.

The method of the present invention uses a heated zone of a temperature of 310 to 345 K through which finely dispersed waste water, e.g.

in droplet or thin film form, is conducted where the oxygen for the metabolism of the thermophilic bacteria is mainly supplied by air, oxygen enriched air or relatively pure oxygen gas and not only by the iimited amount of the dissolved oxygen of the hot waste water.

The use of all devices known to contact oxygen with active microorganisms except the activated sludge method with direct waste water aeration is within the scope of the invention.

In a preferred embodiment the method of the invention is performed in a relatively high tank with a funnel shaped bottom. There is no other condition for the shape of the tank which is closed at its top and bottom. The top is closed by a cover, the bottom by a funnel with a connected discharge pipe. The tank is loaded with filler material as known from the trickling filter technique. This filler material may consist of cinder pieces, ceramic particles, stones or plastic elements. It is essential however that there is a sufficiently large volume of voids and that the inner surface is as large as possible. The filler material does not extend completely to the upper or lower closures. The open volume left near the upper closure houses the waste water distributing device. The lower open volume leads into a discharge conduit.

The tank is charged with waste water from the top. The distribution of waste water onto the surface of the filler material is accomplished by rotary distributors, rebounding plates, perforated plates and similar apparatus known in waste water technique which serve for the most even distribution of the waste water.

The upper open volume is equiped with one or more pipe flanges arranged on the same level with the distributing apparatus. These pipe flanges are used for the aeration of the tank. In case of no additional mechanical aeration the air flows from top to bottom. The air flows from the tank by the discharge pipe. In case of additional aeration the air may be directed through the tank from top to bottom and vice versa. Conduits for the outgoing air are placed correspondingly in the lower or upper section of the tank. To prevent the volume of the tank from cooling, the air passed through may be warmed up. Air pressure increases within the tank is obtained by means of check or back pressure valves and or seal water of the discharge pipe which is drawn out with a siphon. In case of oxygen supply by gaseous oxygen the tank must be closed gas tight.The top closure is effected by a cover, the bottom by syphon as already described above. Additionally a pressure gauge is applied at any point of the tank, most suitably in the upper open volume.

The method of this invention renders the thermophilic treatment of highly polluted waste water practicable without extended retention time and excessive foaming. The retention time in known thermophilic plants is from 7 to 10 days with intensive foaming. The retention time with this invention is reduced, 1 to 3 days without foaming. The microorganisms participating in the thermophilic decomposition are directly supplied with oxygen and not only indirectly with the dissolved oxygen of the waste water. The microorganisms directly absorb through their cell membrane oxygen from the air and or gaseous oxygen which brings about a considerable increase of performance of the microorganisms.

In this way the limiting factor of the reducing capacity of the thermophilic microorganisms, oxygen is influenced. According to the known methods oxygen only was available to the microorganisms from the dissolved oxygen of the hot water of 310 to 345 K. This oxygen supply is very limited because of the temperature dependence of the solubility of oxygen in water and causes long retention in thermophilic activated sludge plants.

As a condition of the method of this invention, oxygen is available to the microorganisms at an essentially higher rate and not limited by the low saturation concentration of oxygen in hot water of 310 to 345 K. The utilisation rate of gaseous -oxygen by the microorganisms is essentially higher compared to dissolved oxygen and may be improved additionally by increasing the atmospheric pressure in the thermophilic treatment chamber.

The performance of the invention is diagrammatically shown by way of example in the accompanying drawings, which show various embodiments of treatment tanks for use in accordance with the present invention.

Fig. 1 shows a closed tank 1, which is provided with thermal insulation 2. Within the upper open volume 3 of the tank the waste water to be treated is conducted from a pump pit 5 with a pump 6 via pipe 7 and finely dispersed by a distributing device 4 onto the filler material 8 which occupies the median part of the tank 1.

Within the funnel shaped lower open volume 9 of the tank 1 the percolating waste water is collected and conducted via discharge pipe 10 into collecting basin 11. From the collecting basin 11 a part of the waste water is drawn to further treatment or discharge into receiving water via outlet channel 12.

The other part is recycled to the pump pit 5 via the opposite outlet channel 13 for repeated percolation through the filler material 8. The oxygen of the air used up by the microorganisms and the air fraction carried with the discharging water are replaced by air flowing in via pipe connecting piece 14.

Fig. 2 shows a tank 1 with essentially the same function as in Fig. 1 supplemented by a heater 15 for the tank sides, a heating installation 16 for the tank and a calorifier 17 for the collecting basin 11.

Fig. 3 shows a tank 1 with essentially the same function as in Fig. 1 and Fig. 2 supplemented by a device 1 8 to exchange the heat of the effluent with the inflowing air and heat exchanger 19 to exchange the heat of the out-going with the inflowing air.

Fig. 4 shows a tank 1 with essentially the same function as in Figs. 1 to 3 but supplied with gaseous oxygen. Via pipe 20 with pressure manometer 21 and regulating valve 22 oxygen is charged into the tank 1. At the lower discharge pipe 23 the gastight lock of the tank is effected by pressure valve 24 or by sealing water which is dilated on adjustable level by siphon 25 with lifting pipe 26.

Claims

1. A method for thermophilic biological waste water treatment in which finely dispersed waste water is conducted through a microorganism treatment zone at a temperature of 310 to 345 K while supplying air or oxygen or oxygen-enriched air to the zone.

2. A method according to Claim 1 in which the treatment zone is confined in a tank closed at top and bottom.

3. A method according to Claim 2 comprising heating the interior of the tank.

4. A method according to Claim 2 or 3 comprising heating the tank sides.

5. A method according to any one of Claims 2 to 4 comprising heating the waste water to be purified outside of the tank.

6. A method according to any one of Claims 2 to 5 comprising heating the tank by introducing warmed air.

7. A method according to any one of Claims 2 to 6 comprising heating the tank and or the waste water and or the air by stream or hot water or warm water.

8. A method according to any one of Claims 2 to 6 comprising heating the air or the waste water introduced into the tank by means of heat exchange with the air and or the partially purified waste water flowing from the tank.

9. A method according to any one of Claims 2 to 8 in which the tank is insulated against heat loss.

10. A method according to any one of Claims 2 to 9 comprising flowing air into the tank via one or more flanges of the tank side at the upper end of the tank to replace the air drawn off by discharge of water from the tank.

11. A method according to any one of Claims 2 to 9 comprising charging the tank with pressurized air.

12. A method according to Claim 1 1 comprising charging the tank with pressurized air at the lower end of the tank and discharging said air at the upper end.

13. A method according to Claim 1 1 comprising charging the tank with pressurized air at the upper end of the tank and discharging it via a waste water discharge pipe at the lower end.

14. A method according to Claim 1 1 comprising charging the pressurized air with excess pressure into the tank and retaining it by appropriate means.

15. A method according to any one of Claims 2 to 9 comprising charging the tank with gaseous oxygen.

16. A method according to Claims 2 to 15 comprising charging the oxygen with excess pressure and retaining it by appropriate means.

17. A method according to Claim 1 wherein the treatment takes place in a tank substantially as described in Fig. 1, Fig. 2, Fig. 3 or Fig. 4 of the accompanying drawings.

18. A device for use in the method of Claim 1 comprising a tank containing filler material, the tank having a closed top, covering means for supplying waste water on to the filler material, and a funnel shaped bottom containing a discharge pipe for waste water, and means for supplying air, oxygen or oxygen enriched air to the interior of the tank.

19. A device according to Claim 18 comprising means for heating the interior of the tank.

20. A device according to Claim 18 or 19 comprising means for heating the tank sides.

21. A device according to Claims 18 to 20 comprising means for heating the waste water to be purified outside the tank.

22. A device according to any one of Claims 18 to 21 comprising means for heating air before introduction into the tank.

23. A device according to any one of Claim 18 to 22 comprising means for heating the tank and or the waste water and or the air by steam or hot water or warm water.

24. A device according to any one of Claim 18 to 22 comprising means for heating the air or the waste water introduced into the tank by means of heat exchange with the air and or the partially purified waste water flowing from the tank.

25. A device according to any one of Claim 18 to 24 in which the tank is insulated against heat loss.

26. A device according to any one of Claims 18 to 25 comprising means allowing air to flow into the tank via one of more flanges of the tank side at the upper end of the tank to replace the air drawn off by the discharge pipe.

27. A device according to any one of Claim 18 to 25 comprising means charging the tank with pressurized gas at the lower end and discharging said gas at the upper end.

28. A device according to any one of Claims 18 to 24 comprising means for charging the tank with pressurised gas at the upper end and discharging said gas via the waste water discharge pipe at the lower end.

29. A device according to Claim 18 substantially as described herein with reference to Figs. 1, 2, 3 or 4 of the accompanying drawings.