Nitrogen Removing Biofilter (NRB) is a passive treatment approach to reduce nitrogen (N) from on-site wastewater. NRBs are comprised of an upper nitrification layer (aerobic, for organic contaminants removal and nitrification) above a denitrification layer (anoxic, for heterotrophic denitrification). Laboratory and field data indicate that the effectiveness of nitrification plays a significant role in controlling the nitrogen removal performance of the overall system. However, the most effective operational conditions (e.g. filtration materials, depth, dosing frequency) have not been elucidated. To elucidate the most effective operational conditions, in this study two sets of experiments were conducted: a) lab-scale columns packed with aged nitrification layer sand, intermittently dosed with synthetic on-site septic tank effluent (STE); and b) pilot-scale columns packed with different filtration materials, dosed with real on-site wastewater. Three lab-scale columns (inner diameter 7.5 cm) were constructed with different depths (15.2cm, 30.5cm and 45.7 cm). 2cm thick geotextile was placed on the top to ensure even distribution of STE. The columns were dosed 8 times per day at the rate of 0.5 gal/ft2.d with anoxic synthetic influent to mimic the on-site STE (TN= 70 mg-N/L, NH4+ = 60 mg-N/L). In parallel, four sets of pilot-scale columns (30 gal) were constructed at Parson’s Trailer Test Center at the New York State Center for Clean Water Technology to test the nitrification performance using real on-site wastewater when different filtration materials are utilized (sand only, sand+silt, sand+crushed oyster shells (OS), sand+ biochar). Nitrogen species (TN, NH4+, NO3 -, NO2-) measurements and carbon measurements (TOC, DOC) along with pH and dissolved oxygen (DO) monitoring are underway to investigate the chemical/biological nitrogen transformations in the vertical profile of the lab-scale columns. The microbial composition in the soil matrix before the experiment and after the three-month operation will be investigated and compared.

Characterization of nitrogen transformation in the nitrification layer of both lab-scale and pilot-scale Nitrogen Removing Biofilters (NRB)

2019 Spring National Meeting

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