Phosphorus Removal in a Pilot Scale Trickling Filter System by Low Level Lime Addition to Raw Wastewater.

摘要

Lime addition to raw wastewater as an upgrading technique can significantly aid a trickling filter plant in producing effluents in compliance with NPDES permit limitations for BOD5, suspended solids and phosphorus. Low level lime addition does not require recarbonation and does not produce the sludges typical of high pH lime treatment schemes. Low level lime addition was studied in laboratory and pilot scale systems. Raw wastewater was treated in a 4.16 cu m/day (1100 gpd) primary clarifier followed by a 2.46 cu m/day (650 gpd) trickling filter system. Lime was added to a rapid mix tank prior to primary clarification at pH levels of 9.0, 9.5 and 9.8 entering the clarifier. Phosphorus precipitation, solid-liquid separation of the insolubilized phosphorus, nutrient levels entering the trickling filter, biological treatment efficiency, sludge production and sludge characteristics were all monitored. Ferric chloride and polyelectrolytes were tested for their effectiveness as flocculating aids in the solid-liquid separation of the insolubilized phosphorus. Results indicate that low level lime addition to raw wastewater in a trickling filter system can provide an effective simple-to-operate, cost-effective method of upgrading a plant to successfully comply with effluent limitations. (Author)