Abstract
An economical and efficient treatment system of waste water from pigpens was developed in a practically applicable size by separating microfine solid particles from water with a pretreatment step. This system was composed of filtration, agglutination and separation. In the filtration step, waste water of approx. 10, 000 pigs was filtered through a screen for separation of solid and large particles. In the agglutination step, a polymeric coagulant was added to the filtrate for agglutination and separation of flocculent fine particles in the filtrate and the mixture was subjected to the treatment with a multi-disk separator and activated sludge process. The microfine solid particles collected from the filtrate were collected together with excessive sludge and subjected to separation and dehydration with a multi-disk separator from the filtrate. The supernatant separated from the filtrate was treated with the activated sludge process. In conjunction with the efficiency of agglutination and separation, approx. 100mg/liter of a cationic polymer coagulant was added to the filtrate, attaining removal rates of SS (suspended solid) and BOD as high as 95.9% and 80.4%, respectively. With an amount of 50mg/liter of the addition of the coagulant, the removal rates of SS and BOD were also so good as 82.7% and 42.5%, respectively. The BOD of the supernatant after separation of the solid matter was 1, 910mg/liter, while the BOD of waste water was 8, 000mg/liter. In the activated sludge process, the BOD loading rate was 0.33kg/m3 per day and the BOD of the treated water was 44.0mg/liter. The removal rates of BOD and NH3-N were as high as 97.7% and 98.0%, respectively. The rate of SS removal of the filtrate after separation of the sludge with the disk separator was also as good as approx. 98%.
The construction cost and the running cost of this system were approx. \5, 000/pig and approx. \1.6/pig/day. The treatment of waste water from pigpens could be substantially improved in terms of both efficiency and economy in comparison with those of the conventional methods for treatment.
