Parameter Optimization Of Municipal Sewage Sludge Composting For Nutritional Soil

Sewage sludge is the sediment produced by urban sewage treatment plants. Sewage sludge is the inevitable product in wastewater treatment, containing such organics as nitrogen, phosphorus and other nutrients. There are also heavy metals, pathogenic bacteria and parasite eggs and other harmful ingredients in it. With the strict requirement to the disposal of urban sewage and the rapid construction of facilities, problems come to be on the rise. Because of the huge number of sewage sludge and the inadequate of sludge treatment facilities in Chongqing, we must find out the safe disposal method, which is technologically advanced, economically viable, and causing less ecological damages, to protect the water environment and people's health in the Three Gorges reservoir area.Based on current situation of municipal sewage sludge in Chongqing, this paper does some researches on the pretreatment of the sludge used as nutrient soil, which can achieve the goal of "reduction, detoxification, stabilization, resources" and eventually solve urban pollution. First, according to the substrate and results of single Compound Microorganisms research, we ascertained the optimal combination. Secondly, we found out parameters, rested on results of orthogonal experimental. Finally, given the relevant parameters, composting was done to the rationality and feasibility of the orthogonal experimental results, and ultimately determined the optimal parameters which can meet the national standards of garden plant nutrition soil.Results of study of parameter optimization were as follows:â‘ results of orthogonal experiment: 1) Changes of physical indicator. The holding times of piles, except experiment 1 and 7, can meet the composting requirements; pH values varied from 5.5 to 8.5, meeting the "urban sewage treatment - Landscaping with muddy "standards;Organic content was between 37.7% and 45.2% after composting, indicating it's suitable for composting; the moisture content ultimately decreased from 1.2% to 5.7%. 2) Changes of biological indicators. Germination indexes of the experiment are ultimately more than 100%. The compost used as a nutritive soil for plants, may be good for plants growth. 3) Visual and variance analysis of orthogonal experiment. Referring to both previous results of single factor experiments and orthogonal experiments, we determined the best combination: A3B3C3D2E3F2.â‘¡results of Verifying experiment: 1) in the results of correlation analysis, heavy metal indicators and K, nitrogen, total phosphorus, available phosphorus was a positive correlation between each two indicators. But organic matter content and total nitrogen content, organic matter content and moisture content were positively related, and the others showed a negative correlation between each two indicators. 2) In contrast to the analysis, variation of physics, nutrients and biological indicators in verifying experiment are the same in orthogonal experiment. Some indexs results of verifying experiment were better than the orthogonal experiment. 3) In the standard analysis of compliance, the indexes of final compost product can meet the standard of landscape plant nutrient soil. 4) Through this validation analysis, the optimal combination of parameters selected is feasible, and the optimal combination is A₃B₃C₃D₂E₃F₂.