Liquid purification or separation – Processes – Chemical treatment
Patent
1997-08-23
1999-10-26
Straub, Gary P.
Liquid purification or separation
Processes
Chemical treatment
210754, 210756, 210759, 210760, 210763, 588205, C02F 172, C02F 176, C02F 178, A62O 300
Patent
active
059722266
DESCRIPTION:
BRIEF SUMMARY
The area of the invention is the treatment of industrial or urban effluents containing organic matter and nitrogen compounds.
More generally the invention relates to the treatment of effluents which contain organic matter and organic and inorganic compounds of nitrogen, such as waste lixiviation products, farm excrements, chemical industry effluents (dyes, explosives, anilines, nicotinic acid, polyamides etc.) effluents of agro-food industries, treatment plant sludge, output effluents from treatment sludge packaging and dehydration etc..
The treatment concerned consists of removing from the effluents to be treated a substantial part of the undesired compounds they contain so that they can be discharged into a natural receiving environment, a treatment facility or a collector network. The effluent considered may be water or any other fluid liquid.
The methods conventionally used to treat urban or industrial effluents use biological processes intended to reduce their biological oxygen requirements (BOR) and their content of nitrogenous nutrients and phosphorus. However, certain effluents containing pollutants that are not easily biodegradable and have high ammonia contents require the use of special processes and/or necessitate the additional use of chemical substrates for their treatment.
One effective treatment adapted to the elimination of chemical oxygen requirements (COR) is aqueous phase oxidation which has been described at length in the prior art. The objective of this technique is to carry out extended oxidation of organic matter that is little biodegradable contained in aqueous effluents through the contact of said effluents with an oxidising agent. For this purpose the operating conditions of said process typically lie between approximately 20 and approximately 350.degree. C. regarding temperature and between approximately 1 and approximately 160 bars in respect of pressure.
Aqueous phase oxidation processes do not allow substantial elimination of ammoniated nitrogen, particularly when the effluents to be treated contain high concentrations of ammoniated nitrogen (>200 mg/l). Even oxidation under wet conditions (Wet Air Oxidation) which is one of the best performing oxidation processes, generally carried out at a temperature of between approximately 200.degree. C. and approximately 350.degree. C. and a pressure generally lying between approximately 20 and approximately 160 bars, only achieves limited removal of ammoniated nitrogen with yields of 5% to 10% whereas organic carbon is destroyed with efficacy in the region of almost 80%. Numerous publications have shown that the treatment of industrial or urban effluents by wet air oxidation only achieves very partial elimination of total Kjeldahl nitrogen of between 5 and 15% and that on completion of treatment the latter is essentially in ammoniated nitrogen form.
Physical processes also exist for the removal of ammoniated nitrogen. Air or steam stripping, effective for high contents, requires considerable investment and is ill-adapted to the treatment of effluents which also contain high concentrations of organic matter. Also, it only achieves ammonia conversion by concentrating it. With this type of process the ammonia is removed by neutralisation with sulphuric acid to form ammonium sulphate which has to be stored before being put to further use, which constitutes an additional operating charge. With treatment by wet air oxidation for example this operation can only be carried out after leaving the effluent to settle, cooling to a temperature of less than 80.degree. C. and adjusting pH in order to prevent simultaneous release of volatile, foul smelling and/or harmful organic compounds during forced aeration at a higher temperature. This treatment of ammoniated nitrogen subsequent to wet air oxidation leads to much increased investment and operating costs.
In treatment plants the removal of ammoniated nitrogen may also be made by biological nitrification-denitrification treatment. This treatment does not easily accept high loads.
If the effluent
REFERENCES:
patent: 4052302 (1977-10-01), Fletcher et al.
patent: 4141828 (1979-02-01), Okada et al.
patent: 4525283 (1985-06-01), Hurak et al.
patent: 4699720 (1987-10-01), Harada et al.
Djafer Malik
Luck Francis
Sibony Jacques
Omnium De Traitements et de Valorisation
Straub Gary P.
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