Effect of earthworm bio-bed treatment on properties of cow manure

Using earthworms for the treatment of organic solid wastes has more advantages than conventional techniques and aroused extensive attention. In this study, cow manure was treated by earthworm bio-bed, and then changes of physicochemical and biological properties of cow manure before and after the treatment were investigated based on laboratory measurements. The results showed that cow manure after the earthworm bio-bed treatment had advantages of better water and air penetrating properties, easy drying and no order. Both water content and electrical conductivity in cow manure significantly decreased, and pH tended to be neutral. The earthworm bio-bed treatment reduced total nitrogen and organic matter content but elevated ammonium and nitrate content in the manure. Total potassium and total phosphorus, including the fractions of organic phosphorus, inorganic phosphorus and available phosphorus in treated manure increased while available potassium decreased. Humic acid content had no significant changes. The removal efficiency of Cr, Cd and Cu by the treatment was better than that of Pb, Mn, Zn and Fe. The treatment process enriched microbial flora, increased catalase activity and reduced urease activity in vermicompost. In addition, the carbohydrates in the cow manure gradually decomposed and changed to humic substances, while water-soluble organic silicon compounds were converted into inorganic silicon oxides during the earthworm bio-bed treatment.