Evaluation of Shallow and Deep Bed High Rate Downflow Denitrification System for NOx-N and Suspended Solids Removal

A biological downflow denitrification filter employing high surface area media was tested at a waste water treatment facility in Ohio to demonstrate its capabilities in cold winter conditions. Testing was carried out to achieve NOx-N to less than 1 mg/l. Additionally, the solids capture capabilities were tested with a view to achieve effluent TSS < 5 mg/l. Four different bed depths were tested during this study. The loading rates and pollutant removal capabilities were evaluated to compare the same with traditional deep bed filters. The filter showed remarkable results with much higher hydraulic and pollutant loading rates while achieving limit of technology pollutant removal even at waste water temperatures below 8 °C. The high surface area media used in the filter allowed high pollutant removal capabilities with higher pollutant loadings, thereby offering significant capital cost savings.