effects of hydrostatic suction and chemical conditioning on upgrading the sludge drying beds' performance

sludge drying bed is preferred to mechanical methods due to the need for very simple technology. due to restriction of natural dewatering, we tried to eliminate some of these limitations by the tests and studies of assumptions. in this study, the effect of hydrostatic suction and sludge chemical conditioning has been studied in the natural sludge dewatering optimization. at first, hydrostatic suction created by water entry and exit control, then by adding ferric chloride in the optimum dosage to the aerobic digested sludge, dewatering process was compared with the control bed. retention time of the sludge cake and quality of effluent from the drainage layer were compared with control pilot. the retention time of sludge cake decreased from 5 days to 2 days and by using inorganic agent with the consistency of 440 mg/lit to the aerobic digested sludge conditioning, it's retention time (production of sludge with the dry solids consistency of 45 percent) decreased from 6 days to 3 days. the third stage of experiment was simultaneous use of chemical conditioning and hydrostatic suction in drying bed and its result was very satisfactory.use of hydrostatic suction can improve physical and chemical characteristics of effluent from the output of bed, such as turbidity, ph, tss and vss, while it increases cod and tds. it should be mentioned that sludge chemical conditioning, increase effluent factors like ts and tds.