Changes of Nutrients and Heavy Metals Contents in Sludge after Composting

The trend in total contents of N、P、K and heavy metals in sludge composting of using different bulking agents had been analyzed.A series of composting tests were investigated.to study the effect of N P K and heavy metals including rice straw,sawdust,coal fiyin ash,phosphate and limestone to the status of heavy metals through composting.The result shows obviously that suldge composting can increase stability of the total heavy metals but the total contents of P and K increased continuously after composting.Acid extraction showed that :the extraction of Zn、Cd、Cr have not effect on different pH,but Cu and Pb do.Composting of medicine sludge can degrade the active of heavy metals to a great extent and,thus,it can be safely recycled in agricultural land.