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A moving bed biofilm reactor with pre-denitrification configuration was fed with a synthetic wastewater containing high chemical oxygen demand (COD) and ammonia. By changing different variables including ammonium and COD loading, nitrification rate in the aerobic reactor and denitrification rate in the anoxic reactor were monitored. Changing the influent loading was achieved via adjusting the inlet COD (956-2,096 mg/L), inlet ammonium (183-438 mg/L), and hydraulic retention time of the aerobic reactor (8, 12, and 18 hours). The overall organic loading rate was in the range of 3.60-17.37 gCOD/m2·day, of which 18.5-91% was removed in the anoxic reactor depending on the operational conditions. Considering the complementary role of the aerobic reactor, the overall COD removal was in the range 87.3-98.8%. In addition, nitrification rate increased with influent ammonium loading, the maximum rate reaching 3.05 gNH4/m2·day. One of the most important factors affecting nitrification rate was influent C:N entering the aerobic reactor, by increasing which nitrification rate decreased asymptotically. Nitrate removal efficiency in the anoxic reactor was also controlled by the inlet nitrate level entering the anoxic reactor. Furthermore, by increasing the nitrate loading rate from 0.91 to 3.49 gNO/m3·day, denitrification rate increased from 0.496 to 2.47 gNO/m3·day.

Optimized methods for simultaneous removal of nitrate, nitrite and ammonium are important features of nutrient removal. Nitrogen removal efficiency in an intermittently aerated sequencing batch reactor (IA-SBR) with multiple filling events was studied. No external carbon source was added and three filling events were considered. Oxidationreduction potential (ORP) and pH curve at solids retention time (SRT) of 20 d were analyzed. Effects of three organic loading rates (OLR), 0.67, 1.0 and 1.5 kgCOD/m3d, and three nitrogen loading rates (NLR), 0.054, 0.1 and 0.15 kgN/m3d, on nitrogen removal were studied. Nitrate Apex in pH curve and Nitrate Knee in ORP profile indicated that the end of denitrification would be achieved sooner. The kinetic coefficients of endogenous decay (kd) and yield (Y) were identified to evaluate heterotrophic specific denitrification rate (SDNRb). In period 2 at NLR of 0.054 kgN/m3d and considering 2 anoxic and 3 aerobic phases, nitrogen removal efficiency was 91.43%.

The elevated levels of nitrate in ground waters are severe menace for human health and environment. The present study examined a new approach for removal of nitrate from high-contaminated ground waters (100 mg.L−1). Citric acid as carbon sources was employed to evaluate the nitrate removal from bioreactors filled with four media: polypropylene, polyethylene, porous Pumice stone and sand collected from local river within 20 month operation. Furthermore, ozonation process was employed to eliminate the residual carbon sources in effluent before transfer to local water network. The denitrification bioreactors seeded with denitrifying bacteria collected from local wells showed high removal efficiency (62–81%). Furthermore, the ozonation process with concentration level of 5 gr.h−1 significantly reduced the chemical oxygen demand. The result indicated that denitrifying bioreactor with citric acid as carbon source is a promising method for nitrate removal from ground water. [ABSTRACT FROM AUTHOR]

Biological nitrogen removal from industrial wastewater (pharmaceutical synthetic wastewater) was studied. Sequencing batch reactor (SBR) and sequencing batch biofilm reactor (SBBR) were utilized to treat ammonium-rich wastewater. No external carbon source was added to the reactors. At nitrogen loading rate (NLR) of 2.5 kg N/(m3·day), the efficiency of ammonium removal from synthetic wastewater in SBR was 86.9%. SBBR ammonium removal efficiency under fixed dissolved oxygen (DO) concentration of 0.3 mg O2/dm3 was 98.4%. Specific nitrification rate (SNR) and specific denitrification rate (SDNR) in SBR were 9.24 mg NH4-+N/(g MLVSS·h) and 18.56 mg NO-3-N/(g MLVSS·h), respectively. Nitrite accumulation rate (NAR) showed high correlation with DO decrement (R2 = 0.983), NAR and simultaneous nitrification and denitrification (SND) had high correlation, too (R2 = 0.976). SND efficiency in SBBR reached 94.1% while ammonium oxidizing bacteria (AOB) were dominant and NAR in SBBR process at the DO level of 0.3 mg O2/dm3 was 90.3%. [ABSTRACT FROM AUTHOR]