Effect Of Nutrients And Heavy Metals By Adding Different Materials In Sewage Sludge

Sewage sludge is an inevitable outcome from wastewater treatment plants. With the development of industry, in conjunction the rapid process of urbanization, there is a dramatic increase in the sewage sludge. It is a valuable organic fertilizer in the agriculture, for lots of nutrients such as nitrogen, phosphorus and organic matter contained in sewage sludge. However, there are also hazardous substance:heavy metals, pathogenic bacteria and organic pollutants in sludge, etc. So sewage sludge should be treated properly before agriculture using.The aim of this paper was to investigate the effects on the moisture content, pH, EC, nutrients and heavy metals of sewage sludge stabilized by inorganic materials,such as quicklime、fly ash. Two parties were to discuss, one was changes on nutrients, the other was deactivating effienciency in metals. Many conclusions are as follows:1. During the stabilization time, the pH decreased gradually, dewatering performance improved and EC showed different changes because of the different additives; organic matter and nitrogen were degraded while phosphorus was steady,this might be due to changed in pH. The maximum degradation rate of organic matter and nitrogen was29%and26%respectively when using quicklime with doses of18%in sewage sludge. Heavy metals in the sludge were passivated and selected. The maximum passivation rate of Pb in sludge treated by quicklime and Pb,Cd in sludge treated by fly ash was16%,22%,13%, and the differences between different treatments were significantly, and chances on availablity of Cr was negligible. Two materials used simultaneously, mutual promotion in deactivating Pb. but the Ni was restrain by the addition of quicklime and restraining role goes weaken in a longer process, so the effect of deactivating Pb,Ni would be better if stabilization time extended appropriately.2. Attapulgite was used to deactivate heavy metals in sludge, it had a high effienciency at initial period than that of later period. All metals were deactivatied at the beginning of stabilization, but in the end,there were Cu, Cr still in deactivating stage. Different deactivating effienciencies reflected in different metals, deactivated state of Pb, Cd, Ni, Zn became lower, the amount of deactivated Cu showed an improvement and Cr has the feeble effect in the whole process.The metals had different performance with the increasing of percentage attapulgite used in sludge, the activited amount of Pb, Cu, Ni, Cr, Zn raised when attapulgite Ⅲ goes up, but Cd declined. The effienciency of deactivating sluge of attapulgite was not ideal as we expected, the maximum of deactivating occurred in the experiment was less than4%.3. Considering degradation rate of nutrients, effienciency of deactivating metal, the cost of raw materials and maximize use of waste, XI (added6%QL and100%FA)was the best treatment and made the most practical applications.