Effect Of Vermicompost On Physiochemical Index And Microbial Community Structure In Degradation Process Of Urban Sludge

With the acceleration of urbanization,the number of urban sewage treatment plants is gradually increasing,so the output of sludge is also increasing.Vermicomposting is a kind of biological treatment technology that is simple in operation,non-polluting,and harmless to the environment.It has been widely studied in recent years.Vermicomposting can reduce,stabilize,detoxify,and recycle sludge.During the vermicomposting process,we found that there was no significant difference in the changes in the early physical and chemical indicators between the control groups and earthworm treatments.However,in the late reaction period,the control groups and earthworm treatments showed significant differences.Because of the relatively small amount of vermicompost in the early,the effect on composting is not obvious.Until the late stage of reaction,the content of vermicompost is increasing,so the effect on compost becomes increasingly prominent.Vermicompost is a product of vermicomposting,with very good physical and chemical properties.According to the previous experimental research of the research group,vermicompost has played a very important role in the sludge degradation process.The use of vermicompost to treat urban sludge has achieved the goal of“using waste to treat waste”.It has found a new way out for vermicomposting products,widened the use of vermicompost and provided a new idea for the treatment of urban sludge.Based on the above analysis,the urban sludge was regulated into 5mm particles and studied in the following research:?1?Determination of the physical and chemical properties of total nitrogen?TN?,ammonium nitrogen?NH₄⁺-N?,nitrate nitrogen?NO₃^--N?,organic matter?OM?,DOC,moisture content,pH,and electrical conductivity?EC?in the sludge to reflect the impact of adding vermicompost on degradation of urban sludge;?2?Using PCR-DGGE technology to preliminary study the effect of vermicompost on the microbial community structure in the degradation process of urban sludge;?3?Preliminary discussion on the ability of microorganisms to use carbon sources through the use of ecological plates?BIOLOG?method.The influence of vermicompost on the utilization of microbial carbon source during the degradation of urban sludge.The test results are as follows:?1?By measuring the physicochemical properties of the sludge,it was found that the addition of vermicompost can promote the degradation of organic matter in the sludge,and the extent of degradation is greater than that of the control group.The results of mineral nitrogen and EC together indicate that the addition of vermicompost can promote the mineralization of organic nitrogen and increase the salinity of the sludge.In the process of organic matter degradation,the addition of vermicompost strengthened the ammoniation,and the amount of ammonium nitrogen was much higher than that of the control group.At the same time,the amount of ammonium nitrogen affected the activity of nitrifying bacteria,and the nitrification rate was weakened.Denitrification was greater than nitrification.As a result,nitrates have decreased in the later period.?2?By studying the effect of vermicompost on microbial population structure in the process of degradation of urban sludge,PCR-DGGE technology was used to determine the changes of microbial population structure during sludge degradation.The results showed that the bacteria in the process of sludge degradation mainly originated from the sludge itself.The addition of vermicompost optimized the micro-environment in the sludge and made the population structure of the bacteria more stable.During the degradation process of sludge,the bacterial population diversity and evenness index both increased first and then decreased.After adding earthworms,this trend was not changed,but the extent of this change was reduced,and the activity and quantity of bacterial populations were reduced.Stay at a high level.?3?The effects of vermicompost on the carbon source utilization ability of microorganisms in the degradation process of urban sludge were studied.The change of carbon source metabolism during the sludge degradation process was analyzed using the BIOLOG method.The results showed that the addition of vermicompost increased the ability of microorganisms to use carbon sources.The increase in the stability of the AWCD value was due to the utilization rate of carbon sources.The carbon source utilization capacity of the30-day vermicompost group was lower than that of the control group.The carbon source utilization ability of the group was stronger than that of the control group.In the first 30 days,the species in the control group was higher than that in the vermicompost group.The degree of carbon source utilization was higher in the control group than in the vermicompost group,and in the 30-50 days the vermicompost group was higher than the control group.The addition of vermicompost increased the utilization of carbohydrates and amino acid carbon sources by microorganisms,increased the ability of microorganisms to utilize polymers and phenolic carbon sources in 30-50 days,and increased the use of carbon in carboxylic acids and amines.The source has little effect.For other five types of carbon sources other than amines,the use of carbon sources for 50 days after adding manure was stronger than that for30 days,especially for carbohydrates and amino acid carbon sources.Species and phenolic carbon sources,carbon metabolism in the control group 30 days before the strong,30-50 days weakened,the introduction of vermicompost changes this trend,so that the ability of microorganisms to use these carbon sources has been improving.There is no obvious effect on carboxylic acids and amine carbon sources.The results of PCA analysis showed that the use of carbon sources was more stable after adding manure.The 0-30 day control group and the plutonium manure group changed along the negative direction of the second principal component.At this time,the difficult to use carbon source of phenolic acids accounted for a higher proportion in the negative direction of the second principal component.The proportion is relatively high,and the utilization of carbon sources is slightly higher.The distance from 30to 50 days is greater in the control group than in the manure excrement group,indicating that the introduction of manure in this type of carbon source has little effect.The results of PCA analysis showed that there was a significant change in the metabolic types of microorganisms after the addition of earthworms,and the ability to utilize carbon sources also changed.Carbon sources that act on PC1 differentiation are mainly carbohydrates and amino acids,followed by polymers,carboxylic acids,and phenolic acids.The carbon sources responsible for the differentiation of PC2 are mainly polymers,phenolic acids,amino acids,amines and carboxylic acids.