Application of a novel Mass Bio System to remove low-concentration ammonia nitrogen from water bodies

Abstract

Water pollution due to ammonia is one of the most serious problems faced by the human beings and other life forms worldwide. With the rapid development of economy, pollution of water resources by ammonium (NH₄⁺) pollutants has increased severely. The water supply system has exceeded its capacity with regard to both quantity and quality of water. Many countries have already established a standard for strict limitation of ammonium nitrogen (NH₄⁺-N) or NH₃ content in drinking water. In this study, a novel Mass Bio System (MBS), a suspended biologically activated carbon granular carrier cubic particle with 2–5 mm side length and a specific gravity of 1.02–1.08, was used for water treatment. In order to find a suitable method for ammonium removal from water resources, synthetic water containing NH₄⁺-N at a concentration of about 10 ppm was treated by MBS. NH₄⁺-N was nitrified to nitrate nitrogen (NO₃⁻-N) by MBS in an inner-circulated fluidized bed reactor continuously. MBS showed an efficient and stable NH₄⁺-N nitrifying performance at temperature of 20–30 °C and DO of 3–4 mg L⁻¹. With an influent concentration of NH₄⁺-N at 10–15 mg L⁻¹, the concentration of effluent NH₄⁺-N and nitrite nitrogen (NO₂⁻-N) was below 0.25 mg L⁻¹, showing an average removal efficiency of above 90% within a hydraulic retention time (HRT) of 30 min. The pH value of effluent water remained at 7.2–7.3 automatically. Removal of load could reach 256.1 mg-N per (L-pellet h) and oxygen uptake rate increased to 1170.9 mg-O₂ per (L-pellet h). The nitrifying process fits to zero-order degradation kinetics. High biomass retention was observed by scanning electron microscopy (SEM).