Patent ID: 7476321
Filing Date: 2009-01-13
Classification: C02F,Y02A,Y02W

Abstract:
1. A method for purifying waste water comprising subjecting the waste water to a treatment in a first zone so as to precipitate phosphorus in a septic tank, after which the waste water depleted of the phosphorus is passed successively through two aerated bio filters each in a tank forming separate zones to obtain a state in which the first bio filter mainly houses heterotrophic bacteria and the second bio filter mainly houses autotrophic bacteria, and discharging the waste water from the second bio filter, a constant amount of the water rich in nitrate from the second aerated bio filter being partly recycled to the phosphorus precipitation zone and a sludge precipitated from at least one of in and after the bio filters being recycled to the septic tank such that the treatment of a load of the waste water is extended to essentially 24 hours a day.