METHOD OF COMBATING BACTERIAL FILAMENTOUS SWELLING OF ACTIVATED SLUDGE Russian patent published in 1997 - IPC

FIELD: waste water purification. SUBSTANCE: invention relates to methods of biological cleaning of household and industrial waste water accompanied with worsening sedimentation characteristics of activated sludge and is aimed at combating or preventing bacterial filamentous swelling of activated sludge at biological sewage disposal plants with elevated loading in what relates to organic pollution, excessive accumulation of filamentous bacteria, and excessive ejection of suspended matters from secondary settlers. Invention is distinguished in the following. Air tanks are successively provided with mixed aeration system - 60% of small- bubble and 40% of middle-bubble, whereupon volume structures are installed, that is, biomass carriers providing 1.5-2 times increase in activated sludge concentration. Activated sludge in quantity 0,0001-0.0002% based on its summary weight in air tanks is then treated with nitrosoalkylurea in concentration 0.04-0.08% for 3-4 h and is grown for 10-12 h on dilute waste water, once again treated with nitrosoalkylurea in concentration 0.05-0.07% and grown for further 3-5 h and charged into air tank in the return sludge intake zone. EFFECT: improved reliability of process. 4 cl, 1 tbl