| Abstract | To overcome the sludge drying beds treatment problems, modification of sludge drying beds were made by providing heated water circulation underneath of the loaded sludge, and were also amended with the covers to protect the rain effects, vectors transmission diseases, and esthetic problems and odor. The efficiency and optimum operating conditions of heated sludge drying bed are investigated in this study. Three sludge hydraulic loading rates SL1 60 liters per batch, SL2, 40 liters per batch, and SL3 20 liters per batch, were applied to the heated beds. Four different heating temperatures, 40°C, 50°C, 60°C, and 65°C were set to study the effectiveness of drying rates, and pathogen removal capacity. As a comparative measure, control beds, with the same design criteria and loading procedures were run, and examined the pathogen reduction, and drying rates. The study results proved that heated sludge drying bed is a promising solution for treating fecal sludge in developing countries. All the sludge loading capacity could produce more than 80% TS in final products in 10-15 days, the biosolid production rate was 125 to 300 kgTS/m²yr, whereas the control beds in the study only produced 40 to 95 kgTS/m²yr. The drying efficiency of heated beds is 3 to 4 times greater than that of control beds. At 65°C,all loading rates could produce Ascaris safe biosolids, while heating at temperature 40°C, would acquire longer drying time, and Ascaris contents were not declined to the safety level. Heating temperature between 50 and 60°C, gave the satisfactory results when drying SL2, and SL3 loading capacities. However, highest temperature in the experimental run 65 °C, is the most effective temperature for all three loading rates, and the final product are Ascaris safe. Regardless of the load of the sludge or the depth of the sludge on the drying bed per area of drying surface, heated drying beds gave about 50% higher rate of TOC% reduction than removal rate in the controls. Total volatile solids were also reduced 40-50% of initial contents. The reduction of that organic matter make the sludge stable, and recover from odors problems, and reduce environmental protection when it is used in the agricultural lands. The overall efficiency of sludge heated drying bed can be summarized that it could produce hygienically safe final product that could be intended for reuse in the agricultural fields. Effluent liquids are free from Ascaris and their carbon contents are much less than the wastewater, and effluents from other treating system of fecal sludge, although it still needs further polishing treatments. It was a simple modification of sludge drying bed, however it proved incredible improvement. |