The effects of limited liming on solar dried wastewater sludges in covered drying beds

Abstract

The purpose of this study was to investigate the effects of limited liming (CaO) in mechanically dewatered sludges from municipal wastewater treatment plant during solar drying in a pilot covered drying bed. The basis for the study was to benefit from the solar energy potential of our country and increase the use of renewable energy sources in environmental investments. A tunnel type greenhouse with 2m x 5m paved bed floor width and transparent polycarbonate cover was designed for the study. Sludge was spread over the concrete floor with a 25 cm. height and mixed twice a day. Limited quicklime (0.15 kg quicklime/kg Dry Solids(DS)) was used to speed up the pathogen microorganism removal. When the limited liming & solar drying method was applied to the sludge of 20% DS content, the legal landfilling requirement of 35% DS content and the USEPA Class A pathogen reduction requirement were achieved in 10 days in summer, and in 20 days in winter.