Study On Aerobic Mixing Composting Technology Of Municipal Sludge In Southern Hebei Province

In recent years,the arbitrary accumulation or landfill of municipal sludge has caused inevitable secondary pollution to the surrounding environment,and sludge composting technology becomes a hot spot of concern in various countries.In this study,the raw sludge of Handan City Wastewater Treatment Plant was used as raw material,and mushroom residue and straw were used as auxiliary materials.Four test groups（A,B,C,D）were set up in different proportions for aerobic composting for 48 days.The temperature,water content,pH value and other indicators were measured.Correlation analysis between the ratio and the index and the inside of the index was carried out to comprehensively investigate the effects of different ratios on the composting effect.After the composting,the temperature of all the four piles reached the standard of harmless hygiene.The total nitrogen increased by 8.33%,18.69%,25.13%and 22.84%compared with the initial compost,and seed germination index was 83.12%,86.56%,90.81%and 92.51%,all of which were more than 80%non-toxic to plants.Based on the results of correlation analysis,it could be seen that the content of excipients was significantly negatively correlated with C/N and water content,and was extremely negatively correlated with organic matter.In order to investigate the maturity of each pile and optimal ratio under the sludge compost,this study combined the results of correlation analysis,carried out principal component analysis on the measured indicators,and selected the most representative indicators as evaluation factors.The factor was then used to calculate the weight of each factor by using the entropy weight method.The maturity of each pile was evaluated by the grey relation analysis under the mean method and the weight method.Finally,the response surface method was used to optimize the ratio.The results showed that the apparent index,the days of pile temperature above 50℃,the water content,the degradation ratio of carbon-nitrogen ratio,NH₄⁺-N/NO₃^--N,and the seed germination index could be used as the evaluation factors of sludge compost maturity.According to the analysis of the grey correlation method,it was concluded that the maturity of pile C and pile D was higher,that of pile C was better,and that the maturity grade was better.According to the solution result of the response surface method,it was found that the ratio of the maximum predicted value of the response value F was sludge:mushroom residue:straw=1:0.77:0.03.The conclusions obtained by the grey correlation method were basically consistent,and the optimization result was the best ratio.In order to further investigate the effect of initial conditions on the compost effect,this study was based on the optimal mixing ratio,and tested three levels of initial water content,C/N,and bacterial agents,and the degree of influence of each factor was reflected by analysis of variance.The results showed that the pile with water content of55%maintained for 6 days above 55℃,with the greatest reduction of organic matter.Meanwhile,The pile with C/N=25 and bacterial agent 3 had the longest high temperature period,the largest seed germination index,and the best effect of composting.Water content of 55%,C/N=25,and bacterial agent 3 were the best initial conditions for this municipal sludge mixed compost.According to the analysis of variance,it could be seen that the difference in water content had a significant effect on organic matter and seed germination index,but had a small effect on temperature.The difference of C/N had a significant effect on temperature and organic matter,and had a greater effect on organic matter,but had little effect on seed germination index.At the same time,compared with the water content,C/N had a stronger influence on the compost effect.This study investigated the effects of the optimal ratio and initial conditions on the compost effect and determined the best municipal sludge compost treatment parameters,which provided a theoretical basis for the sludge harmless treatment and resource utilization.