Feasibility of Chemical Extraction Sewage Sludge in Land Utilization

A batch of experiments of the heavy metals contaminated sewage sludge with L-aspartic acid, nitrilotriacetic acid, DL-malic acid and malonic acid were conducted to investigate the effects of chemical extraction sludge to heavy metals' form (Cu, Zn, Pb, Cr) , the loss of nutrient elements and the crop growth status and heavy metal accumulation after sludge applied, and also to analyze the feasibility of chemical extraction sludge in land application. Results show that, the highest removal rate of Cu, Zn, Pb, Cr is up to 89.1% , 32.4% , 52.7% , 39.2% respectively,and the content of the unstable state of heavy metal in sludge was reduced significantly after chemical extraction. As a result, the security of chemical extraction sludge in land application was also significantly improved. After chemical extraction, although the variable range of the total nitrogen and total phosphorus in sludge loss rate are 9.0% 92.0% and 56.4% -77.3% respectively, it can still maintain the good fertilizer efficiency and satisfy the need of land use. When the right amount of sludge is applied to farmland, the dry weights of wheat are increased sharply. However, the accumulations of heavy metals in wheat root and shoot are also increased with the increase of sludge. So the appropriate ratio of sludge and soil is 50% when taking wheat growth status and heavy metal residues into consideration.