Investigation of the Effectiveness of Drying Cow Dung and Sewage Sludge in Sand Drying Bed

Abstract

This study investigated the effectiveness of dewatering cow dung and sewage sludge in sand
drying bed. Sewage sludge and cow dung and sewage sludge were used to conduct seepage
and evaporation experiments using standard methods. Results show that initial moisture
contents were 81.01% and 74.07% for sewage sludge and cow dung. Comparison of
Dewatering ratio between sewage sludge and cow dung on short term basis after 7 days of
drying was 0.821, while dewatering ratio on long term basis between sewage sludge and cow
dung after 13 days of drying was 1.03. Cow dung dewater faster through seepage than
sewage sludge on short term by 17.92%, but on long term basis, better dewaterability of
2.99% was observed in sewage sludge. The initial volume of water in both cow dung and
sewage sludge was 0.11342 m3. Cumulative moisture loss from evaporation is higher in cow
dung than in sewage sludge by 2.88%, because the final volume of water in both sludges
were 0.050411 m3 and 0.052237 m3 representing 44.45% and 46.06% moisture contents
respectively. Overall percent moisture loss in sewage sludge was 55.55% and 53.94% in cow
dung which indicate effective dewatering because of the insignificant difference between
dewatering in sewage sludge and cow dung. It is concluded that sand drying beds can serve
as better alternative to expensive cow dung rotary dryer.