An Improved Vermicomposting System Provides More Efficient Wasterwater Use of Dairy Farms Using Eisenia fetida

Dairy cattle farming produces large amounts of wastewater and it causes environmental
pollution and eutrophication of rivers, but the nutrients in the waste could be recycled. Here, an
improved vermicomposting system was applied to dairy farm wastewater, and wastewater with a
nitrogen content of 100 mg/L and 200mg/L tested with different combinations of organic substrates
such as cow manure and rice straw in rural solid waste. Results showed that earthworms could
continuously grow, wastewater (N 100mg/L) mixed with rice straw corresponding to the most
significant gained weight for Eisenia fetida earthworms (2.38 to 9.12-fold), and the earthworms’ weight
was positively correlated with the C/N ratio, organic matter content, and pH. Compared to the
initial state, the system significantly changed physicochemical parameters in nutrients, such as
the percentages of total nitrogen, phosphorous, and potassium, which were found to increase in
vermicomposting while organic matter content, C/N ratio, and cellulose declined as a function of the
vermicomposting period, and the final vermicompost was better for the absorption of plants. These
results suggest that continuous wastewater addition improved the effective transformation of organic
waste to allow valorizing a broad range of organic residues, and avoid the risk of environmental
pollution in dairy cattle farming.