Safe Utilization of Municipal Sewage Sludge in Agriculture and Forestry

Abstract

Municipal sewage sludge has been increasingly produced in China with the development of municipal wastewater treatment. The use of sewage sludge as a fertilizer and soil amendment has resulted in high concentrations of heavy metals in the soil and food limiting its use. Controlling the pollution of heavy metals is the key factor to realize the safe utilization of sewage sludge. The present study was carried out to find scientific basis to the appropriate sludge applications in agriculture and forestry. Pilot experiments inEucalyptusforest showed that the total yield and nutrient amount ofP.hydridumwere significantly higher thanA.marorrhiza, the annual average yield in dry weight and total nutrient amount ofP.hydridumwere 21.32 thm-2and 1248.2 kghm-2, respectively, 9.18 times and 3.58 times that ofA.marorrhiza, soP.hydridumwere more suitable to be the converting plant from sludge to biochar or organic fertilizer. After plants treatment, the maturity of sludge increased significantly, water content and soluble heavy metals decreased obviously, so that the agricultural safety increased, and the all indicators were conformed to the sludge requirements for agricultural use. In addition, theEucalyptustrees grow well with a large spread of sewage sludge. Nutrient contents ofEucalyptusforestland soil increased and heavy metal contents of the topsoil beneath the sludge did not significantly increase.