The impact of hydraulic retention time on an anaerobic reactor’s nitrogen removal effect

Abstract:

At present, domestic research on anaerobic denitrification is mostly at the laboratory stage. In order to develop highly efficient and suitable denitrification equipment for production, this study uses a self-designed anaerobic reactor with clinoptilolite as the filler, and naturally cultivated biofilm. By connecting the reactor to the primary biofilter of RAS, we aim to preliminarily investigate the reactor’s nitrogen removal effect under different hydraulic retention times (HRT), with a view to direct subsequent research. The results show that during the experiment, the reactor has a good removal effect on inorganic nitrogen (IN) and total nitrogen (TN). When the HRT is short (HRT<7.43 h), ammonium (NH4+-N) is the main form of nitrogen removed from the reactor, whereas with longer HRT (HRT≥7.43 h), nitrogen is removed as nitrate (NO3–-N). When the HRT is 17.52 h, the reactor’s nitrogen removal efficiency is the best, and the removal rate of NO3–-N reaches 77.48%. As HRT continues to extend, the nitrogen removal efficiency decreases. The better the nitrogen removal effect, the greater the accumulation of nitrite (NO2–) and ammonium, with the former accumulating first. Thus, this study can provide reference for the development of anaerobic denitrification equipment.