Use of sunflower stalks as a bulking agent in sewage sludge composting

Abstract

The aim of this study was to investigate the compostability of sewage sludge (SS) with sunflower stalks as a bulking agent (BA) and determine the optimum mixture ratio. Four reactors were operated for a period of 21 days using SS with BA concentrations of 50%, 40%, 30% and 20% on wet-weight basis. During the composting process, the pH, electrical conductivity (EC), dry matter (DM), organic matter (OM), organic carbon (OC) and total and inorganic nitrogen (N) contents were determined. Temperature variations, losses of organic C and total N were determined over a 21-day period. It was found that the optimum SS stabilization occurred for the 60% sewage sludge and 40% sunflower stalk mixture (R2). This mixture reached a maximum temperature of 55 degrees C and the thermophilic phase in this reactor continued for 8 days. The highest carbon lost (37.1%) was also observed in this reactor. Sunflower stalks were determined to be a promising bulking agent for sewage sludge composting.