Research On Key Technics Of Urban Sewage Sludge Composting As Fertilizer

Sewage sludge is the byproduct of sewage treatment, with a lot of water, silt, fibers, residuals of animal and plant in it. Water content and volume of sewage sludge is high, also it contains hormones, toxic organics, heavy metals and different kinds of mineral wastes, all of which have a continuous toxicity. Once discharged wantonly it would enter the food chain easily and may cause serious secondary pollution to the environment and human beings. Whereas there are some organic and useful elements in sewage sludge and made it an available resource for secondary utilization. Land use after composting is a good choice of resource utilization and may be a main means of sludge disposal in the future.Thermophilic aerobic composting study is carried on based on the condition of the sludge from Liaoyang sewage treatment plant in order to find out whether the sludge can be used as biology compound fertilizer or soil amendment, and to achieve key technics of composting.First of all, the fermentation device and its control system are designed.Secondly, analysis the parameters such as temperature, water content, pH value, EC, VS, WSOC and NH4+-N of thermophilic aerobic composting process based on different humic content, different kinds of compost amendment and different adding ratios of the amendment. The investigation shows natural air-dried and then mixed with conditions is a better way of sludge dewatering. Among sawdust, rice husk and rice straw, after mixed with sawdust, the compost can achieve a better maturity, and the best adding ratio of sludge, sawdust and mature compost that returned is 3:2:3.Thirdly, evaluate the toxicity of the compost production of secondary fermentation according to the GI of comparative tests and try to find the best using quantity.At last, give the maturity determination of compost production based on the physical, chemical and biological indices.