Liquid purification or separation – Processes – Treatment by living organism
Patent
1997-12-22
1999-10-12
Woo, Jay H.
Liquid purification or separation
Processes
Treatment by living organism
210620, 210908, 210910, 4352625, C02F 300
Patent
active
059650249
DESCRIPTION:
BRIEF SUMMARY
The invention pertains to a process for the microbiological degradation of alkylene amine acetates under alkaline conditions, using microorganisms present in activated sludge.
Such a process is known from an article by N. Gschwind in GWF Gas-Wasserfach: Wasser/Abwasser Vol. 133, 10 (1992), 546-549, which describes how ethylene diamine tetraacetate (EDTA) can be degraded in a model system in a continuous reactor. EDTA-containing water was treated with immobilised microorganisms from industrial treatment plant activated sludge enriched to that end on a special carrier material (foam polyurethane PUR REA 90/18, fine).
There are several drawbacks to the process described by Gschwind. For instance, it was found that effective degradation of EDTA is only achieved at a pH of 9-9.5. In actual practice, however, it is preferred to employ a more neutral pH in waste water treatment plants in order not to cause an adverse effect on the various reactions taking place with the aid of the other microorganisms present. Moreover, surface water managers prefer the discharge of a pH neutral effluent from water treatment plants. In Gschwind's experiment, at a pH of 8.5 the degradation of EDTA is sharply reduced over time. According to Gschwind, a pH of less than 9 really is not feasible. There is also the fact that the use of carrier materials as applied by Gschwind is objectionable because the amount of solid waste formed, which needs to be treated as chemical waste, may well be increased. Moreover, it is not possible to use carrier materials just like that in "conventional," activated sludge based water treatment plants. Gschwind reports that cultures not attached to carriers proved unsuccessful. Besides, it is not clear from the article that EDTA degradation continues to be effective in effluent which contains other carbon sources in addition to the EDTA.
It has now been found that waste water which contains alkylene amine acetates and, optionally, other contaminants can be effectively purified at a pH of about 8-9 by making use of microorganisms in flocs, without the need to employ a special carrier material for the microorganisms. It was found that in this process not only EDTA but also other alkylene amine acetates, for instance propylene diamine tetraacetate (PDTA), were microbiologically degradable.
The process disclosed in the opening paragraph is characterised in that alkylene amine acetate-containing waste is contacted, at a pH of about 9 or less, with activated sludge containing a wide range of microorganisms, in the absence of specific carrier materials.
It should be noted that Japanese prepublished patent applications JP-A-6296990 and JP-A-6335384 disclose the use on a carrier material of special bacteria of the Pseudomonas editabidus-1 type, which bacteria, when fixed on a carrier, are capable of degrading EDTA. However, the use of activated sludge containing a wide range of microorganisms at a specific pH is neither mentioned nor suggested.
Further, B. Nortemann in Applied and Environmental Microbiology 58 (1992), 671-676 discloses that, in general, EDTA has poor biodegradability, but that 98% degradation of EDTA in model systems can be achieved by immobilising bacteria on sand. Preference is given in this process to the use of a mixed culture of microorganisms because of the synergism occurring among the different bacteria. The importance of maintaining a specific pH is neither disclosed nor suggested. Also, the enrichment of microorganisms with a complex, EDTA-containing medium was again found to be impossible. Only with glyoxalate, glycine or ethylene diamine present as a carbon source in addition to EDTA was inhibition not observed.
Pre-published patent application JP-A-58043782 discloses how EDTA is degraded in a closed bottle test using specific Pseudonomas and Alcaligenes bacteria. Said special testing method employs pure cultures of these bacteria, this to solve the problem of unsatisfactory EDTA degradation in, say, activated sludge plants using the wide range of bacteria present in the sludge.
Beside
REFERENCES:
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Applied and Environmental Microbiology, B. Nortemann, "Total Degradation of EDTA by Mixed Cultures and A Bacterial Isolate", Feb. 1992, p. 671-676, vol. 58, No. 2.
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Nikolaus Gschwind, "Biodegradation of EDTA in a model waste water", pp. 1-7 (translation of German article GWF Gas-Wasserfach: Wasser/Abwasser vol. 133, 10 (1992) 546-549.
Boelema Eltjo
Van Ginkel Cornelis Gijsbertus
Akzo Nobel N.V.
Fennelly Richard
Mancini Ralph J.
Prince Fred
Woo Jay H.
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