Performance of Moving Bed Biofilm Reactors for Biological Nitrogen Compounds Removal from Wastewater by Partial Nitrification-denitrification Process

In this research, the continuously operated laboratory scale Kaldnes (k1) moving bed biofilm reactors (MBBRs) under partial nitrification-denitrification process were used for treatment of synthetic wastewater containing ammonium and glucose. The Anoxic and Aerobic reactors were filled to 40 and 50 %( v/v) to attach and retain biomass with k1 biofilm carriers, respectively. The favorite internal recycle ratio and hydraulic residence time (HRT) to eliminate nitrogen compounds were 300% of inflow rate and 20 hours, respectively. Optimal dissolved oxygen (DO) was 1-1.5 mg/L in the aerobic reactor. No sludge was returned into the system and only an internal recycling was performed from aerobic to anoxic reactor. The results showed that the maximum and average specific nitrification rate (SNR) in the aerobic reactor were 49.4 and 16.6 g NOx-N/KgVSS.day, respectively and the maximum and average specific denitrification rate (SDNR) as 156.8 and 40.1gNOx-N/KgVSS.day in the anoxic reactor, respectively. The results also showed that it is possible to reach a stable partial nitrification with high ratio of NO2-N/NOx-N (80% to 85%) during high load ammonium and low DO concentration (<1.5 mg/L) in the aerobic reactor. During optimum conditions, the average removal efficiency of total nitrogen (TN), ammonia and soluble organic carbon (SCOD) occurred as 98.23%, 99.75% and 99.4%, respectively. This study showed that the partial nitrification/denitrification process in the moving bed biofilm reactors system has an acceptable performance for treatment of wastewater with high load of organic carbon and organic nitrogen compounds.