Effects of Vermicomposting on Physicochemical Properties and Microbial Biomass of the Sewage Sludge

The changes of earthworm biomass, microbial biomass and physicochemical properties of compost were studied so as to explore the vermicomposting process of fresh dewatered sewage sludge. As a result, the daily weight gain, cocoons, growth and reproductive rate of earthworm increased significantly at the end of vermicomposting. As compared with the original sewage sludge, the TOC content in the vermicompost decreased by 22.15 %, the EC value increased by 2.79 times, the content of available nitrogen, available phosphorus and available potassium increased by 87.83 %, 66.46 % and 19.28 %, respectively, the number of bacteria, fungi and actinomycete increased by 3.8, 0.97 and 0.33 times, separately. However, the TOC value of the control group without earthworm fell by 30.06 %, the EC value increased by 0.98 times; the content of available nitrogen, available phosphorus and available potassium increased by 8.69 %, 96.26 % and 7.16 %, respectively, the number of bacteria, fungi and actinomycete increased by 2.04, 1.48, and 0.59 times, respectively. Thus, the earthworm greatly affected the physicochemical properties and microbial biomass of the sludge during the vermicomposting process.