Nutrient Transformation in Co-composting of Undigested Sewage Sludge With Rice Straw

Land utilization is an economical and popular disposal methods of sewage sludge. But proper treatment such as composting is necessary before it is applied to land. Two different composting styles including mechanic turning and forced aeration piles were studied in the experiment. The results showed that the total contents of P and K increased continuously during composting. Total N increased less than total P and K because of ammonia volatilization. Available P increased during the first period, but they decreased during later maturing period, while available K increased continuously. Water soluble total N, -N and -N followed the similar trend than available P. It is about 50d for an appropriate composting time when composting with undigested sludge and rice straw.