Method of sewage treatment

Liquid purification or separation – Processes – Treatment by living organism

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Details

210627, 210631, 210747, 210758, 210903, C02F 172

Patent

active

051145871

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

the present invention relates to treatment of different kinds of wastewater, wherein the amount of dissolved organic compounds by addition of nitrate compounds is reduced as well as the fact that formation of hydrogen sulphide is prevented.


PRIOR ART

Treatment of wastewater is as an important and costly operation in society. Several methods are developed and at work. Municipal wastewater is characterized by the composition of mainly the following parts:
Municipal wastewater is characterized by the following data:
BOD.sub.7 refers to biological oxygen demand which said used as a measure of the content of easily degradable organic matter in the water.
The FIG. 7 indicates that it is the oxygen demand during seven days in a sample kept in darkness at 20.degree. C. which is intended. TSS refers to total suspended solid sand designates the amount of non-solved constitutents in water or sludge. Chemical oxygen demand is called COD and defines the consumption of a certain oxidation agent, converted into oxygen demand, at oxidation of mainly organic materials in water under specified conditions. Kjeldahl-N defines that the content of nitrogen is determined according to Kjeldahl's method.
Society of today has gradually increased its demands for treatment of wastewater. At present there are demands for >90 percent reduction of BOD.sub.7 TSS and phosphorus for municipal wastewater. Increasing demands and a large-scale production advantages have led to the building of large, centrally placed, wastewater. Increasing demands and large-scale production advantages have led to the building of large, centrally placed, wastewater treatment plants in many municipals. This has resulted in extensive pipe line systems for transport of wastewater fro the more peripheral parts of the municipals up to the wastewater treatment plant. In many cases the time of residence can be 1 to 2 days in the pipe line system. Thereby poisonous and corrosive hydrogen sulphide is formed under anaerobic conditions.
In spite of the fact that many different methods for treatment of municipal wastewater have been developed, the present technique might roughly be divided into the following partial steps:
In order to increase the efficiency of the wastewater treatment plants chemical precipitation has more and more been used in connection with pre-sedimentation, so-called pre-precipitation, whereby almost all particularly bonded pollutants can be separated. However, solved BOD is not separated to any larger extent. The sludge separated from presedimentation and biological treatment is often stabilized by means of digestion in a digester, whereby inter alia methane gas is formed. The gas is usually flared but in recent years it has more and more begun to be used for energy production.


DESCRIPTION OF THE INVENTION

The object of the present invention is to reduce the amount of organic pollutants, especially oxygen demanding substances, in an early stage, and/or to prevent that solid pollutants are transmitted into a solution phase. This gives an overall better treatment and reduces the load of the subsequent steps, which increases the possibilities for additional connections and/or new treatment processes.
The proposed process is based on the following assumptions: only a part of the biochemical oxygen demanding material is present in a soluble form. treatment step that added nitrate will have time to be consumed, preventing the total nitrogen amount in the effluent to be increased by the addition. concerning BOD.sub.7, TSS, N and P.
At the process according to the invention the pipe line net or other residing volume are exploited for the following purposes: solved or colloidal compounds which are difficult to separate.
The method can be used i larger sewer nets, in average sized or large wastewater treatment plants, in smaller wastewater treatment plants, in wastewater plants for single households or in connection with the handling of sludge in transport vehicles as well as for industrial wastewaters with a high amount of o

REFERENCES:
patent: 3335082 (1967-08-01), Ullrich
patent: 3525685 (1970-08-01), Edwards
patent: 3705098 (1972-12-01), Shepherd et al.
patent: 4911843 (1990-03-01), Hunniford et al.
Itou, "Concentrating method for sludge", Patent Abstract 108 C 59, 1979, (JP 56-38196).
Sekikawa, "Purification of organic waste water by activated sludge", Chemical Abstracts, vol. 81, 1974, p. 208 (16507d).

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