Simultaneous biological removal of nitrogen and phosphorus in a vertical bioreactor

Abstract

Nutrients pollution has become a global environmental threat. A large fraction of nutrient pollution is caused by point sources like the discharges of untreated domestic and industrial wastewater. As a result, there is a great demand to develop reliable, compact and efficient nutrient removal technologies. In the wastewater industry, most of the bioreactors have a large foot print with a plane configuration. Furthermore, the existing nutrient removal processes are based on well-known microbial species of genus Nitrosomonas and Nitrobacter involved in nitrification/denitrification and Candidatus Accumulibater Phosphatis responsible for biological phosphorous removal (BPR). The present work is unprecedented in two aspects: (1) The biological nitrogen and phosphorus removal from wastewater occurred in a multistage vertical, tubular bioreactor and (2) Two abundant microbial species were responsible for the simultaneous nitrification–denitrification–BPR in this vertical bioreactor. The abundant microbial populations included an unidentified bacteria of Saprospiraceae family and bacteria affiliated with the genus Zoogloea. The composition of the synthetic wastewater used in this study was: total phosphorous (TP) 32.6±0.7mg/L, total nitrogen (TN) 272±7.5 in which 45±1.8mg/L was ammonia-nitrogen (NH3-N). The bioreactor was continuously operated for over 350 days at constant flowrate, temperature and pH of 240 (L/day), 22–24 (°C) and 7–7.5. The results showed that simultaneous nitrification–denitrification–BPR was the dominant process by an, as yet not fully classified, microbial species. The effluent TP and TN concentrations were 2.7±0.4 and 4.3±1.2mg/L respectively. Concentrations of NH3-N, NO2− and NO3-N in the effluent were 0.7±0.1, 0.8±0.5 and 0.3±0.1. The simultaneous nitrification–denitrification–BPR was highly effective delivering above 90% TN and TP removal efficiency. The successful results presented in this paper have led to the construction of a 20,000L/day demonstration plant in the City of Pickering, Ontario.