An effective technique of sludge separation is required for excess sludge of sewage or wastewater plant. The separation of bulking sludge of paper manufacturing plant was studied using DAF(Dissolved Air Flotation) system. The effects of parameters such as nozzle type, A/S(air/solid) ratio, pressure, injection time of pressured water and saturation time were examined. The results showed that the best nozzle type was flat which had small orifice hole. The optimum A/S ratio and pressure were 7.070×10-3(recycle ratio of pressured water : 20%) and 5 atm, respectively. Injection times of pressurized water around 20-25 sesc and flotation time of 30 min appeared to be optimal for the DAF operation. The order of performance of packing was 18 mm > 22 mm > 32 mm.

• 김동석(대구가톨릭대학교 환경과학과) | Dong Seog Kim
• 박영식(대구대학교 보건과학부) | Young Seek Park Corresponding Author