OPTIMIZATION OF A HIGH-RATE COMPOSTING OF BARLEY DREGS WITH SEWAGE SLUDGE

Sewage sludge alone is used as composting feedstock which produces poor quality compost due to the low organic carbon and high moisture content even with a costly dewatering process in place. In order to solve these problems, high-rate composting process treating with barley dregs and sewage sludge was developed. A central composite design (CCD) was used to investigate the variation of carbon decomposition rate and total volatile solids (TVS) as a function of mix ratio and moisture content. The results of temperature, CO2 evolution rate and TVS loss rate show that the organic matters in the barley dregs and sewage sludge were biodegraded completely within 5 to 7 days. The TVS loss rate and CO2 evolution rate at higher temperature indicated the high degree of mineralization due to the higher activities of microorganisms. The optimum range of mix ratio and moisture content was found to be 35-40% and 55-60%, respectively. The results of seed germination test suggest that the compost was matured enough to be used in land farming