Effect of vermicomposting using Eisenia foetida on properties of sewage sludge

Key words: 
• earthworm /
• sewage sludge /
• physichemical properties /
• nutrients /
• heavy metal

Abstract: Vermicomposting of sewage sludge using Eisenia foetida directly, compared with not adding earthworm, the change of earthworm biomass，physiochemical properties (pH, EC, ash and TOC), nutrients (nitrogen, phosphorous and potassium) and heavy metal (Cu, Zn, Pb and Cr) in sewage sludge were studied during experiment. The results suggested that earthworms could adapt well to the living environment of direct add sludge during vermicomposting, and that the average growth and reproduction were 0.7 g/d and 4.81cocoon/d respectively. With increased time, vermicomposting showed significant change of chemical properties and nutrients and heavy metal content. After vermicomposting, the results indicated significant reduction in pH value (7.83 to 7.03) and TOC (32.32% to 23.59%), while significant increase in EC (0.46 S/m to 2.23 S/m) and ash (43.89% to 57.53%). The percentage of nitrogen, phosphorous and potassium in vermicompost was found to significantly increase by 37.48%, 19.96% and 20.14% respectively. At the same time, earthworm activity resulted in a significant decrease of heavy metal content of sludge. The order of earthworm absorbing the heavy metal was Cu＞Zn＞Cr＞Pb. After vermicomposting, the production showed small aggregate traits obviously, no odor and maggots.