Liquid purification or separation – Processes – Treatment by living organism
Patent
1998-06-08
2000-04-11
Simmons, David A.
Liquid purification or separation
Processes
Treatment by living organism
210622, 210623, C02F 320
Patent
active
060484608
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the biological treatment of waste water, in which a mixture of activated sludge and waste water is treated with gas in an activation stage and the activated sludge is separated off from the treated waste water by flotation.
Processes of the said type have been disclosed, for example by German Patent Application P 44 11 991.7, which is herewith incorporated by reference. In a process of this type, the sludge leaves the activation stage together with the hydraulic load, the treated or purified waste water, and is separated off from the hydraulic load by flotation in a separation stage and in part recycled to the activation stage, in order to keep a defined sludge concentration in the activation stage. Because of this method of operation, there is a dependence between the sludge concentration in the activation stage and the sludge concentration in the efflux stream from the separation stage, which is recycled to the activation stage, the so-called return sludge. The sludge concentration in the activation stage is thus determined by the mixture of the recycled sludge and the virtually solids-free waste water. The sludge concentrations in the activation stage set in this manner are usually 5 g/l (cf. the abovementioned patent application). This sludge concentration is an important parameter in the dimensioning of biological waste water treatment plants, since it determines, inter alia, the volume of the activation reactor, the volume decreasing with increasing sludge concentration. Waste water treatment plants which could be operated at relatively high sludge concentrations would therefore be desirable, if they did not have some serious disadvantages. A disadvantage of such plants is that the flotation part, depending on the sludge concentration, must be made very large, and thus becomes correspondingly very expensive. Operating these flotation plants is, moreover, difficult, since they react very sensitively to changes in the waste water flow rate. Furthermore, the operating costs are very high, since the high water flow rate necessary for the flotation is a direct (proportional) function of the sludge concentration.
It has now surprisingly been found that these disadvantages are considerably reduced if a process of the type mentioned at the outset is modified in such a way that the concentration of the activated sludge in the activation stage is .gtoreq.6 g/l and that the flotation is a pressure-relief flotation.
The invention therefore relates to a process for the biological treatment of waste water, in which a mixture of activated sludge and waste water is treated with gas in an activation stage and the activated sludge is separated off from the treated waste water by flotation, wherein the concentration of the activated sludge in the activation stage is .gtoreq.6 g/l and wherein the flotation is a pressure-relief flotation. Preferred embodiments of the process according to the invention are given by claims 2 to 3.
BRIEF DESCRIPTION OF THE DRAWING
The Figure is a process flow diagram of an embodiment according to the invention.
A first preferred embodiment of the process according to the invention is that the concentration of the activated sludge in the activation stage is .gtoreq.8 g/l, preferably .gtoreq.10 g/l, particularly preferably .gtoreq.12 g/l. A further preferred embodiment is that the suspension to be taken off for the flotation is conducted at a flow velocity .gtoreq.0.3 m/sec against the natural direction of bubble rise, the suspension is additionally treated with gas in this case by means of a gas-treatment apparatus, the gas-treated suspension is taken off at the bottom of the gas-treatment apparatus and fed to the flotation as described, for example, in P 44 11 991.7.
Individual, or a plurality of, the individual features mentioned in the embodiments can also each be solutions of the invention per se, and the individual features can also be combined as desired.
The advantage of the process according to the invention is essentially that both the activ
REFERENCES:
patent: 3980556 (1976-09-01), Besik
patent: 4085041 (1978-04-01), Fullerton et al.
patent: 4430225 (1984-02-01), Takamatsu et al.
patent: 4443337 (1984-04-01), Otani et al.
Patent Abstracts of Japan No. 63310697 dated Dec. 4, 1989.
Horz Wolfgang
Lohe Hans
Zorn Friedhelm
Hoechst Research & Technology Deutschand GmbH & Co. KG
Prince Fred
Simmons David A.
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