Nitrogen Bio-kinetics

Tertiary and advanced treatment of wastewater improves water quality, to meet environmental concerns but also as a potential source of water for reuse. Rapid deep-bed filtration of secondary effluent is a tertiary treatment that can effectively remove particles and to some extent organic matter; however ammonia and nitrite are not easily removed. This study examined the feasibility and the performance of a pilot bio-filtration system at filtration velocity of 5-6 m/h, enhanced by addition of hydrogen peroxide (HP), for particle, organic matter, ammonia and nitrite removal. Hydrogen peroxide was used as a bio-specific oxygen source to support oxygen demand for full nitrification. The use of HP is advantageous upon aeration due to solubility limitations of the oxygen. As a result of bio-filtration enhanced by 27 mg/L HP, influent concentrations of 4 mg/L N-NH4+ and 0.65 mg/l N-NO2 were removed during the short hydraulic residence time (HRT). In comparison, filtration without HP addition only removed up to 0.6 mg/L N-NH4+ and almost no N-NO2. DNA metagenome analysis of the media biomass demonstrated a community structure and potential function reflecting significant nitrogen cycle-related species (29% of the total community), with low community diversity dominated by Nitrospira species. It is hypothesized that HP addition increased biofilm growth and thickness and as a result, more anoxic microniches were formed; which enhanced anoxic activity supported by the higher availability of oxidized nitrogen due to intense nitrification.