Transformation of Nutrients and Organic Matter in Vermicomposting of Sewage Sludge and Kitchen Wastes

This study was conducted to compare how the nutrients and organic matter content in household kitchen wastes and sewage sludge transform in 120-days vermicomposting experiment. The concentrations of nitrogen, phosphorous and potassium increased during the experiment. The dry matter content of the composts decreased and the value of pH in the case of kitchen wastes increased and for sewage sludge vermicompost it remained almost unchanged. The amounts of organic matter and nutrients decreased to half of the initial masses, but the concentrations of nutrients increased remarkably both in kitchen wastes and in sewage sludge and sawdust mixtures as a result of vermicomposting. Vermicompost made from kitchen wastes contained 3.3% total nitrogen, 0.7% total phosphorous and 5.8% potassium. In the case of the vermicompost made from sewage sludge and sawdust the corresponding indicators were: 2.4% total nitrogen, 0.2% total phosphorous and 0.3% potassium. Small-scale vermicomposting of both household kitchen wastes and sewage sludge turned to be efficient.