effect of natural substances in upgrading the performance of sludge drying beds

utilization authorities in sewage companies considered to sludge dewatering methods due to problems and challenges in this field. dewatering by sludge drying beds is considered in present study. this method 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 impact of using natural substances on the top layer of the bed and increased permeability coefficient of the drainage layer survived. for this purpose, a layer of a hemp gunny and water cooler straw that their c / n ratio are high and this character is useful for production of sewage sludge compost is used as a natural substance on the bed. effects of these hypothesis has been studied on two sections; at first step the capability of natural substances in replacement of the sandy layer platforms by changing of drainage layer's thickness has been investigated and second time by no change in thickness of sandy drainage layer and spend the use of this material on the sludge drying bed has been studied. in this study, retention time of the sludge cake and quality of effluent from the drainage layer were compared with control pilot. based on the results of this study, using natural substances can improve process of urban sewage sludge dewatering, thus the retention time on the drying bed decrease significantly. by reducing sludge retention time on the bed, the main disadvantage of these beds that require large space platforms to construct will be reduced to a significant extent. using these natural substances can improve physical and chemical characteristics of effluent from the output of bed, such as turbidity, ph, cod and tds, while it increases tss and vss.