ECSM’08, European Conference on Sludge Management, Liege,

1-2 September 2008, Belgium

Mechanically dewatered sewage sludge containing 20% dry solids (DS) from an extended  aerated municipal wastewater treatment plant was dried up to 90 % of DS content using solar energy at a pilot scale covered drying bed. Sludge drying was accomplished at a periods of 46 days, 37 days, 45 days, and 60 days during the spring, summer, autumn, and winter seasons, respectively. Depending on the solar radiation variations, solar drying of sludge hardly provides the necessary pathogen control and reduction of vector attraction targets. Lime (CaO) was added to the mechanically dewatered sludge of 20% DS at the beginning of solar drying period. The minimum amount of lime needed was determined as 15% of the DS content of sludge. Similar correlations in solar drying rates for the sludge and the lime added sludge were observed for each season.