Selection of bulking agents for composting of sewage sludge

Abstract

The scope of this work covered: laboratory determination of bulk density, air-filled porosity, mechanical strength, water holding capacity of bulking agents, i.e. straw, woodchips and sawdust, and composting mixtures of sewage sludge and selected bulking agents at the ratios of 1:0.3; 1:0.6; 1:1 (d.b.), as well as simulation of bulk density and air-filled porosity in function of composting pile depth for the composting mixtures. Simulation of changes in bulk density and air-filled porosity was performed for a 2 m high composting pile. The results showed that mixing sewage sludge with woodchips in the ratio of 1:1 (d.b.) allows optimal moisture content, C/N ratio and air-filled porosity across the composting pile.