Liquid purification or separation – Processes – Treatment by living organism
Patent
1997-07-17
1999-10-26
Wyse, Thomas G.
Liquid purification or separation
Processes
Treatment by living organism
210605, 210621, 210630, 210151, 210188, 210218, C02F 330
Patent
active
059722193
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process and an apparatus for the aerobic treatment of waste water in an aerated reactor into which the effluent to be treated is fed at the bottom.
BACKGROUND OF THE INVENTION
The biological treatment of waste water can essentially take place in two ways, i.e. aerobically by making use of microorganisms which use oxygen, and anaerobically by growth of microorganisms in the absence of oxygen. Both methods have found their place in the art of waste water treatment. The first method is used mainly when there is a low degree of contamination, at low water temperature and as a polishing treatment. The second method offers advantages especially as a pretreatment for more severe organic contamination and at higher water temperature. Both methods are adequately known.
Nowadays anaerobic reactors are frequently placed in series with aerobic reactors. such as, for example: ("polishing") for extensive removal of BOD/COD; nitrogen; sulphur for removal of sulphur.
To an increasing extent the existence of aerobic and anaerobic reactions which take place simultaneously in the same reactor is also being reported. Examples of these are nitrification/idenitrification reactions and denitrification under the influence of sulphide oxidation.
Anaerobic processes can also be the reason for low sludge growth figures in highly loaded aerobic systems. The use of a relatively low oxygen pressure in a reactor containing agglomerated (flocculated) biomass can lead to rapid conversion of oxygen-binding substances by aerobic bacteria which are present in the outer layer of the flocs. These bacteria preferably store the nutrition as reserves in the form of polysaccharides outside their cells.
Subsequently the bacteria get no opportunity to use these reserves because of lack of oxygen, and these reserves therefore start to serve as a substrate for anaerobic mineralization processes in the interior of the floc, where no oxygen can penetrate. As a result a simultaneous build-up and break-down of the polysaccharides is produced, the polysaccharides also serving as an adhesive for the cohesive bacterial culture. Protozoa can also play an important role as bacteria-consuming predators with a low net sludge yield.
In this context the term micro-aerophilic is indeed used to indicate that less oxygen is fed to the system than would be necessary by reason of a complete aerobic reaction. This has the result that a bacterial population develops which can multiply under a very low oxygen pressure. A disadvantage of these conditions can be that foul-smelling substances can be produced, such as H.sub.2 S, NH.sub.3 or volatile organic acids. These can be stripped off by air bubbles and pass into the outside air. It can therefore be important that this air is collected for treatment if necessary.
On the other hand, it is important that sufficient inoculating material remains present in the reactor and that the flocs formed are not flushed out before the anaerobic mineralization processes have taken place.
Recent research has revealed that anaerobic bacteria can have a high tolerance to oxygen (M. T. Kato, Biotech. Bioeng. 42: 1360-1366 (1993)). The addition of oxygen can sometimes also be advantageous for an anaerobic process, for example for suppressing sulphate reduction in fermentation tanks, as described in EP-A 143 149. in this latter process, organic solid waste present in a slurry is converted with the generation of a gas which contains methane as the main constituent, also containing a small proportion of up to 3%, and more particularly 0.1-1.5% by vol., of oxygen.
The retention of biomass in a reactor for waste water treatment is of essential importance for the capacity of said reactor. In conventional aerobic treatment this is usually achieved by continuously returning the sludge (=biomass) separated off outside the reactor, by means of settling, to the aeration tank where the biological reactions take place. This process in which the sludge concentration in the aeration tank is 3-6 g/l, is
REFERENCES:
patent: 4009098 (1977-02-01), Jeris
patent: 4451372 (1984-05-01), Rovira
patent: 4482458 (1984-11-01), Rovel et al.
patent: 4530762 (1985-07-01), Love
patent: 5147547 (1992-09-01), Savoll et al.
patent: 5338445 (1994-08-01), Zumbragel et al.
patent: 5518618 (1996-05-01), Mulder et al.
Patent Abstracts of Japan, vol. 007, No. 219, Sep. 1983.
Patent Abstracts of Japan, vol. 013, No. 431, Sep. 1989.
Patent Abstracts of Japan, vol. 12, No. 11, Jan. 1988.
Patent Abstracts of Japan, vol. 12, No. 501, Dec. 1988.
Patent Abstracts of Japan, vol. 007, No. 061, Mar. 1983.
Driessen Wilhelmus Johannes Bernardus Maria
Habets Leonard Hubertus Alphonsus
Paques B.V.
Wyse Thomas G.
LandOfFree
Process for aerobic treatment of waste water does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for aerobic treatment of waste water, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for aerobic treatment of waste water will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-759982