Effect Of Earthworm On Sewage Sludge At Agricultural Chemical Characteristics

The present paper is aimed to meet the resource utilization of municipal sewagesludge to provide data support for agricultural application. Based on earthwormecological function, direct vermicomposting of sewage sludge by Eisenia foetida insummer and fall （set as A1and B1）was conducted in a lab-scale experimentalsetup. The earthworm biomass, sewage sludge physiochemical properties, nutrientsand microbial population was tested during pot experiments with35days. Thefeasibility of vermicomposting technology to recycling dewatered sludge without anytreatment by the earthworm in summer and fall was investigated, and the performancewas evaluated. Discussing whether Eisenia foetida of sewage sludge domesticationcould vermicompost in different seasons which temperature and humidity wassuitable for, and provided the convenience of the resource utilization of municipalsewage sludge.Studying on the variation of agricultural chemical characteristics in sewagesludge during vermicomposting from July to October in2013, the main works weredone as following:(1) The earthworm biomass was tested in order to know the adaptive capacity.(2) The sewage sludge physiochemical properties were tested periodically inorder to choose vermicomposting product that was more suitable for agriculturalutilization.(3) The nutrients in the composts were tested periodically in order to understandthe vermicomposting process.(4) The microbe quantities of three major groups were monitored so as todetermine the dynamic change and its possible relationship with earthworms.The results are as follows:(1) The weight and cocoons with A1and B1showed significant increasedduring vermicomposting,and the earthworms could adapt well to the fresh sewagesludge environment. At the end of expermient, the wetght of earthworms addition was79.77%and82.98%, the number of cocoons was15.94and16.49, the growth rate andthe reproductive rate with every earthworm were9.96mg/d,5.31×10-2cocoon/d and10.44mg/d,5.49×10-2cocoon/d for A1and B1, respectively. (2) Vermicomposting significantly modified the physical and chemical propertiesand nutrients (p＜0.05). Vermicomposting resulted that pH declined upto7.02withA1and7.05with B1, while the electrical conductivity increased317.31%and317.65%respectively. Meanwhile,A1produced15.27%,21.03%,87.83%,66.36%and19.28%increases in total phosphorus, total potassium, available nitrogen,available phosphorus and available potassium as well as34.29%and18.65%decreases in organic matter and total nitrogen as compared to initial after35days ofearthworm inoculation. In contrast, B1produced17.53%,22.67%,92.92%,63.39%and20.06%increases in total phosphorus,total potassium, available nitrogen, availablephosphorus and available potassium as well as35.88%and20.59%decreases inorganic matter and total nitrogen as compared to initial after35days of earthwormactivity.(3) Vermicomposting significantly modified the microbial population(p＜0.05).At the end of expermient, the population of bacteria, fungus and actinomycetesreduced75.47%,70.50%and69.50%with A1and76.08%,67.77%and69.69%withB1.(4) A comparative study on vermicomposting of sewage sludge between A1andB1resulted that were non-significant. Earthworms in summer and fall could getcomposting product which were suitable for farming by vermicomposting.