FINE GRIT REMOVAL CHALLENGES IN WASTEWATER TREATMENT PLANTS

Fine grit consists of abrasive solids and failure to remove grit from the treatment process results in wear of mechanical equipment and sedimentation in tanks, basins and digesters. Grit handling and disposal are increasingly difficult tasks because many grit removal systems yield a final product that is high in organic content and retains a lot of moisture, making it highly susceptible to decomposition and odor generation. Desired degree of washing, space constraints, and available budget are some of the factors that determine which system will most closely serve the needs of a community. Fine grit removal challenges at each WWTP may be different depending on native grit characteristics and plant processes employed. Proper sampling prior to design will determine sizing requirements necessary to achieve a specified removal performance. Most grit enters the WWTP during peak flow events, scouring out the collection system, therefore testing of the grit load should be performed during these periods. This paper discuss about fine grit removal systems and present data from pilot studies carried out in City of St. Petersburg, Florida at Southwest Water Reclamation Facility (SWWRF) and Northwest Water Reclamation Facility (NWWRF).