|
Raw cow manure was treated by a 4-step integrated system with phase separation anaerobic digestion and algal culture. When the first methane fermentation was performed by the effluent from the acid fermenter with retention time of 4 days, the everage biogas production rate was 977ml/l culture/ day. Gas productivity compared to conventional single-stage anaerobic digestion increased up to 31.4 %. As the 2nd methane f ermenter was fed by the effluent from the first methane f ermenter with 4 days of retention time, average amount of 428ml/l culture/day of biogas was produced. The reduction rate of COD in the effluent from the acid fermente;the 1st and the 2nd methane fermenter were 71.8 %, 42.6% and 24.0% respectively. Finally, we examined algal treatment process for the effluent from the 2nd methane fermenter. A semi-continuous culture of Chlorella sp. PSH3 was conducted by feeding the effluent with retention time of 10days. In this process, the production rate of algal biomass and COD reduction rate were averaged 1.8g/l culture/day(2.8 x 106 cells/ml) and 73%, respectivery. Through the 4- setp treatments, the total chemical oxygen demand was reduced from 51,300ppm to 85ppm. Therfore, the reduction rate of total chemical oxygen demand reached about 99.8%. The results indicate that the integrated system could be applicable for treatment of organic wastes, concurrently producing biogas and algal biomass.
|