The Study Of Urban Sewage Sludge Applicated For Mining Wasteland Ecological Restoration

The disposal of urban sewage sludge is the issue that both environmental protection workers and government concerns about, sludge production and the cost of its disposal is increasing continually, which makes the disposal of sludge becoming a burden of municipal construction and urban development. The topic start with the perspective of city - outskirts material cycling, taked the suburban wasteland as the target place to pile up sludge; And made major conclusions as follow through typical characteristics study of sewage and sludge of Nanjing, stability and solid-state fermentation test of sludge, and environmental risk assessment for the sludge application.(1)In the typical sewage sludge of Nanjing, except the organic matter, the composition of TN, TP and TK was slightly higher than the national average, and the Cu, Zn was higher than agricultural standards of acidic soil, whos the average superstandard rate was 4% and 170%; Besides, Cd, Ni was also elements with strong activity, especially the Cd was a highly toxic. The availableln of it was 17.4-32.4% (with EDTA extraction), 18.3-30.9% (with M3 extraction). Cr and Pb were more stable heavy metals, had lower possibility to cause environmental pollution or toxic plants.(2)Several municipal sludge solid-state fermentation methods was designed in the experiment. Took straw and dregs of medicine as a conditioner, mixed fermented with a rate as 1:1(volume), 21 days the basic stability of the sludge had basically compeleted.(3)After fermentation of different materials, nutrient content of fermentated straw and the dregs heap of medicine were in significantly different trends, in which the quality of straw compost TN scores dropped by 26 percent, while dregs heap of medicine of TN remain basically unchanged. Fermentated heap can maintain a of high temperature above 50℃for 7 days, the effective of straw was better than dregs heap of medicine, and the fermentated heap that added with EM bacteria showed a better thermal effect.(4)Soil column study showed that the rehabilitation and irrigation of the plant of soil-mining area should be carried out before the rainy season to avoid unnecessary NO3-leaching, experiments showed that the content of Cd and Ni which leached from liquid was very low, they had no major impact to environment. Cd was in the slow movement, but Ni showed a strong migration at the very beginning.