A Low Cost Solution to Reduce Total Nitrogen Discharged from WWTPs – Meeting the 3 mg/L Regulatory Limit in Total Nitrogen Using Existing Downflow Tertiary Media Filters as a Medium for Denitrification
Existing tertiary media filters for solids removal may be used as a medium for denitrification of the secondary effluent to reduce the Total Nitrogen (TN) discharged by a Wastewater Treatment Plant (WWTP). This study explores the use of tertiary media filters as a low-cost solution for WWTPs in reducing TN levels to meet upcoming nutrient discharge regulations. Three pilotscale filters with sand and anthracite as the media were tested with the secondary effluent of a WWTP. The filter with anthracite (5 feet) were found to perform better than the filter with sand (5 feet) with a nitrate-nitrogen (NO3-N) removal rate as high as 140 lbs of NO3-N removed/1,000 ft3/day in the anthracite column. The TN-N and NO3-N concentrations in the effluent of this column with anthracite were found to be about 1.66 mg/L and 0.67 mg/L, respectively, for a hydraulic loading rate of 4 gpm/ft2. The influent temperatures to the columns ranged from 14 oC to 21 oC during the study. The study continues to increase velocities through the columns at the time of this writing.