Nitrogen transformation dynamics in macrophyte-assisted high-rate vermifilter treating real domestic sewage

Abstract

Due to economic and ecological sustainability, vermifiltration has become a popular alternative to conventional wastewater treatment methods. However, the science behind nitrogen removal in vermifiltration has yet to be adequately explored. Additionally, no study is available on assessing the performance of vermifilters/macrophyte-assisted vermifilters (VFs/MAVFs) at higher hydraulic loading rates (HLRs), which has been a significant loophole regarding the vermifiltration technology. The present study investigated the performance of a MAVF in terms of nitrogen transformation dynamics during the treatment of real domestic sewage subjected to higher HLRs. The designed MAVF ensured a decent removal of ammonium nitrogen (NH4+-N), total Kjeldahl nitrogen (TKN), organic nitrogen, and total nitrogen (TN). In contrast, there was a considerable gain in effluent nitrate nitrogen (NO3−-N) concentration than its influent concentration. The highest removal of NH4+-N (98.2 ± 0.7 %), TKN (99 ± 0.5 %), and organic nitrogen (100 %) corresponded to the experimental run with an influent COD of (200 ± 25) mg/L and HLR of (3 ± 0.1) m3/m2-d, whereas the experimental run with an influent COD of (200 ± 25) mg/L and HLR of (7 ± 0.2) m3/m2-d resulted in the maximum increase in effluent NO3−-N concentration (73 ± 10.6 times its influent concentration). The maximum TN removal of (87 ± 2.2) % was achieved for the experimental run with an influent COD of (700 ± 45) mg/L and HLR of (3 ± 0.1) m3/m2-d. The present research reinforces the suitability of MAVF technology as a cost-effective and ecologically benevolent bio-remediation alternative for domestic sewage.