Effect Of Earthworms On The Abundance Of Pathogenic Bacteria On Vermicomposting Treatment Of Municipal Sludge

Municipal sludge contains a large number of pathogenic microorganisms.Improper treatment and disposal will lead to high pathogenic pathogens into the environment,causing disease transmission,seriously threatening public health and ecological security.Vermicomposting is a kind of environmentally friendly and sustainable urban sludge treatment technology.In particular,it is an effective management tool for organic solid waste for developing countries owing to its low operational costs and high value vermicompost.However,a major obstacle to the widespread acceptance of vermicomposting as a general organic solid waste management alternative is a lack of the removal potential of pathogenic microorganisms during vermicomposting.Therefore,studying the regularity and mechanism of pathogenic bacteria in the process of sludge treatment can not only provide risk assessment for the treatment of urban sludge by earthworms,but also improve the efficiency of sludge sanitation and safety utilization.The effect of earthworm action(activity,intestinal digestion,mucus)on pathogen index in municipal sludge degradation process was studied,and its mechanism was preliminarily explored.It is mainly divided into three parts: firstly,the relationship between earthworm density and pathogen index was studied in the process of sludge stabilization,and the correlation between physicochemical index and pathogen index was analyzed using SPSS19 and Canoco5.Secondly,through the short-term digestion of earthworm gut passage,the effects of the intestinal tract on pathogenic bacteria were investigated.Finally,the effect of mucus on the degradation of sludge was investigated by adding different amount of earthworm mucus.The main results are as follows:(1)Earthworms can accelerate the degradation of sludge.The organic matter of the sludge decreased from 78.14% to 68% after the introduction of earthworms,and the conductivity increased from 80 m S/m to 255.3 m S/m.Analysis of the compost product by EEM revealed that the protein-like content of the compost product(tryptophan-like and tyrosine-like)decreased significantly.Vermicomposting has a role in reducing the abundance of pathogens during the process.After the introduction of earthworms,the removal rate of total coliform bacteria reached 86%,the removal rate of fecal coliform bacteria reached 90%,the removal rate of E.coli was 99%,and the earthworm density did not affect the reduction of pathogenic bacteria lately.It was found that the variation of pathogen index was positively correlated with the easy utilization of nutrient substances by the analysis of SPSS and Canoco.This kind of nutrients may be like tryptophan,such as amino acid.(2)After a short-term digestion of the intestinal tract,the total coliform and Salmonella populations increased,and the fecal coliform and E.coli counts decreased by 76% and 82%,respectively.This shows that intestinal digestion is selective for the reduction of pathogens.(3)Earthworm mucus can accelerate the degradation of sludge.After adding mucus,the organic matter in the sludge could descend from 81.62% to 79.27%,DOC from 54.76 g/kg to 39.86 g/kg after 15 days.It can be seen from EEM that the protein-like substance of the 4th and 8th days of the added mucus is decreased obviously.The removal rate of total coliform,fecal coliform,E.coli,Salmonella was up to 77%,88%,92.5% and 83%,respectively.It shows that mucus has obvious inhibitory effect on pathogenic microorganisms.In addition,through the use of 0.2?m filtration membrane filtration treatment of mucus found that the decrease of mucus to pathogenic bacteria mainly depends on the complex chemical antibacterial substances in the mucus.In conclusion,this experiment with Eisenia fetida as tested earthworms that studied the effect of earthworm action on the abundance of pathogenic bacteria in the process of degradation of municipal sludge.The mechanism of the reduction of the abundances of the pathogenic bacteria was preliminarily studied.It is found that earthworms can reduce the abundance of pathogenic bacteria during composting.The abundance of pathogens is closely related to the substrate's easy use of nutrients,intestinal digestion of earthworms,and earthworm mucus.That's provided a reference for the goal of safe and sanitary utilization of the vermicompost municipal sludge and the subsequent study of pathogen between vermicomposting.