Study On Optimization Of Key Influencing Factors And Humification Mechanism Of High Efficiency Aerobic Composting

Wasted activatied sludge?WAS?from wastewater treatment is one of the world's largest organic solid wastes.Due to the high pollution risk caused by its direct discharge to the environment,China pays more and more attention to the safe treatment and disposal of WAS.WAS aerobic composting cannot only realize its reduction and harmless,but also the compost products can be used as organic fertilizer or soil improver,which has good environmental,social and economic benefits.It becomes one of the important routes of WAS treatment and disposal.Rapid aerobic composting process using reactors has become a research hotspot in recent years due to short compost cycle,good product quality,small secondary pollution and high degree of automation.Firstly,the initial acidification problem during rapid aerobic composting was solved by phosphate addition in the present study.Then,the pile temperature and its duration were optimized and the influence of initial moisture content on the post-maturity efficiency was studied.Finally,the effect mechanism of phosphate addition on the humification was analyzed.The relevant research results can provide theoretical and practical references for the practical application of rapid aerobic composting in my country.It is of more important academic significance and practical value.The main research content and findings are as follows:?1?Study on the mitigation mechanism of phosphate addition to the acidification problem in the early aerobic composting process.When the molar ratio of HPO₄^2-and H₂PO₄^-was 2:5,the pile pH was controlled between 6.0?8.5 and the acidification problem was effectively alleviated.The ammonia nitrogen content was increased by 51.14%.It helped to increase the nitrogen content of compost.At the end of composting,the seed germination index was 75.18%and the degree of maturity was good.?2?Study on the influence of the pile temperature and duration on the composting effect.When the medium temperature stage lasted for 24 h and the high temperature stage lasted for48 h,the composting process was started normally,and the organic matter conversion and humus synthesis are both effective.Compared with the medium temperature stage lasting for36 h,the contents of soluble organic carbon?DOC?and soluble polysaccharides were increased by 10.74%and 12.89%,respectively,when the medium temperature stage lasted for24 h,.At the end of composting,the contents of humus?HS?and humic acid?HA?was increased by 4.86%and 17.98%,respectively..?3?Study on the effect of material moisture content on post-naturity efficiency.When the moisture content of the post-maturity material was in 55%-65%,it was favorable for the further decomposition of the residual organic matter in the pile,and the post-maturity efficiency was better.In the post-maturity process,the appropriate moisture content increased the DOC and soluble polysaccharide contents by 42.50%-61.84%and 96.59%-98.29%,respectively.At the end of post-maturity,the nitrate nitrogen content in the heap was increased by 55.68%-61.56%,and the HS content was increased by 12.29%-30.67%.?4?Study on the mechanism of phosphate promoting humification of the heap.Phosphate addition promoted the production of humus precursor materials in the heap and increased the degree of humification by promoting the release of soluble polysaccharides from sludge and improving the activity of microorganisms.At the end of composting,the ammonia and nitrate nitrogen contents of the phosphate-added pile was increased by 91.95%and 25.76%,and the HS and HA contents was increased by 20.33%and 23.80%,respectively,compared with the addition of potassium chloride.The humification index and the degree of polymerization were increased by 23.81%and 13.21%.The addition of phosphate not only increased the humus content,but also caused a more complicated humus structure.