Liquid purification or separation – Processes – Treatment by living organism
Patent
1999-05-26
2000-06-20
Wyse, Thomas G.
Liquid purification or separation
Processes
Treatment by living organism
210614, 210625, 210631, 210906, C02F 330, C02F 312, C02F 300
Patent
active
060774304
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to optimized control of processes for the simultaneous removal, by the biological route and physicochemical route, of the phosphorus present in effluents, in particular sewage.
BAKGROUND OF THE INVENTION
The principle of biological dephosphatation is based on the ability of certain bacteria, known as poly-P bacteria, to accumulate phosphorus in the unstable form of polyphosphate complexes or of adenosine triphosphate (ATP). This accumulation takes place under aerobic or anoxic conditions, in the presence of dissolved oxygen or of nitrates. This aerobic accumulation is preceded by an upstream anaerobic stage, during which stage the poly-P bacteria carry out an anaerobic fermentation on the organic matter resulting from the sewage, in order to convert it into readily assimilable molecules: volatile fatty acids (VFA). These volatile fatty acids are subsequently converted by the poly-P bacteria into storage materials, known as poly-.beta.-hydroxyalkanoates (PHA). The compound generally linked to these conversions is poly-.beta.-hydroxybutyrate (PHB). In carrying out this conversion, the poly-P bacteria draw energy from the depolymerization of the intracellular polyphosphate stores. This process is accompanied by the release of soluble phosphorus, in the form of orthophosphates, into the medium. The return to aerobic or anoxic conditions is accompanied by the reverse process. The poly-P bacteria accumulate soluble phosphorus in the form of intracellular polyphosphates (ATP), using the PHB accumulated previously as energy source. This process is accompanied by disappearance of phosphorus from the soluble phase.
The mechanisms involved during the anaerobic phase (FIG. 1a) and aerobic phase (anoxic phase--FIG. 1b) have been summarized in the diagram of FIGS. 1a and 1b in the appended drawings.
Two possible configurations of the pathway employing biological dephosphatation have been illustrated, as non-limiting examples, in FIGS. 2a and 2b in the appended drawings. These configurations comprise a sequence of anaerobic 1, anoxic 2 and aerobic 3 regions (FIG. 2a) or anaerobic 1 and aerobic 3 regions (FIG. 2b). In addition, the pathway comprises a clarifier 4 (secondary clarifier), the function of which is to separate the biological sludge from the treated effluent, it being understood that this plant comprises, upstream of the regions 1, 2 and 3, conventional means for degritting, degreasing and optionally primary clarification. A portion of the sludge originating from the clarifier 4 is recycled at the head to the anaerobic region 1, the remainder going to bleed-off.
An example of a biological dephosphatation process is disclosed in German Patent document DE-A-3,902,626. In this publication, soluble organic compounds (organic carbon) are added to the water to be treated and the turbidity of the water and the phosphate content are measured at a single point, in the aeration tank, after separation of the sludge, and, by virtue of the two measurements thus obtained, the supply of air is regulated in the aeration step, as is the addition of acetic acid. The object of this known process is to accelerate biological dephosphatation and more particularly denitrification. It is mentioned in this prior publication that dephosphatation by the physicochemical route (addition of reagents precipitating phosphorus) constitutes a disadvantage.
Experience shows that, in practice, this process is often difficult to control as the forms of phosphorus accumulated within the bacterial cells are very unstable. A relatively short residence time in an anaerobic medium is sufficient for release of phosphorus into the soluble phase to take place.
The lack of reliability of processes employing a biological dephosphatation is often due to two main factors: carbon, which is reflected by a fraction which is too low and often variable over time of the readily assimilable COD in the sewage; prolonged residence times in the clarifier, which is reflected by operating problems.
These factors ma
REFERENCES:
patent: 4160724 (1979-07-01), Laughton
patent: 4488967 (1984-12-01), Block et al.
patent: 4948510 (1990-08-01), Todd et al.
patent: 5076928 (1991-12-01), Ballnus
patent: 5288405 (1994-02-01), Lamb, III
patent: 5798043 (1998-08-01), Khudenko
Chudoba Pavel
Pujol Roger
Degremont
Wyse Thomas G.
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