Effect of Natural Substances in Upgrading the Performance of Sludge Drying Beds

According to the fact that almost all forms of mechanical dewatering needs foreign specific technology, special efforts were concentrated to optimize the use of drying beds.The main disadvantage of sludge drying beds is their large land requirement. This will limit the use of conventional drying beds to areas where sufficient land is available. To optimize and facilitate the operation of sludge dewatering beds, some assumptions are considered in this study that their purpose is to compare the technical characteristics of effluent and the retention time of sludge cake on the bed with control pilot.In this study, the capability of natural substances in replacement of the sandy layer platforms by changing drainage layer's thickness has been investigated. Also, at second step with no change in the thickness of sandy drainage layer, the use of this material on the sludge drying bed has been studied. Natural substances must be used for applying research hypothesis. One of the basic conditions in creating the best habitat for microorganisms in the production of high quality compost is carbon to nitrogen ratio. Microorganisms need carbon resources to supply energy and new cells materials and also, nitrogen resources for protein production. Thus, paying attention to the ratio of carbon to nitrogen in the compost material and the process of preparation is necessary. Therefore, one of the most important parameters in compost preparation from swage sludge is the C/N ratio in the output unit of sludge dewatering. The use of materials with high carbon such as straw, wood chips and sawdust in sludge dewatering process can increase C/N ratio in the sludge cake. In this study, cross bed drying doesnt affect studies; thus, cylindrical pilot is used to simulate a drying bed. Important points in preparing pilots are recommended to be the height of bed and desirable gradated constituent materials. Three pilots were made for this research. One of the pilots was produced as a control pilot with regard to the characteristics of the conventional drying beds and the two others were prepared and established with changes in their structure based on the research assumptions.For simulation of test beds, sand and gravel features recommended in references were used. The properties of sand used for pilot preparation were approved with sieve analysis in soil mechanics laboratory.For easy access to the output of aerobic digester, the pilots were set beside the sludge drying beds in a treatment plant of Tehran city after preparation.Aerobic stabilized sludge was discharged in 20 cm height at pilots and sampling was done with special containers. The effluent sampling was carried out after 3 hours from the time of discharge of sludge on the platforms and tests were performed before 6 hours. Drying process was studied by sampling and moisture measurement of sludge cakes from control and test beds in the future days.