Biological nutrient removal in bench-scale membrane bioreactor and full-scale sequencing batch reactor under various configurations and conditions

Abstract

<p>Biological nutrient removal was studied and modeled for a submerged bench-scale membrane bioreactor (MBR). Of the five configurations studied, the configuration with mixed liquor recirculation to the anaerobic compartment and permeate recirculation to the anoxic compartment gave the best results with 92.3% sCOD, 75.6% TN, 62.4% TP removal, and almost complete nitrification (97.7%) at 25 days SRT and 2 hrs anaerobic, 2 hrs anoxic and 8 hrs oxic HRTs. When recirculation rates were varied within the same configuration, the highest TP removal was 88.1% with 300%/100% (mixed liquor/permeate) recirculation while the highest TN removal (90.3%) was with 200%/300% recirculation. TN and TP concentrations as low as 4.2 +/- 0.1 mg/L and 1.4+/- 0.2 mg/L were obtained, respectively. The BiowinRTM AS/AD model, calibrated against a set of experimental data, predicted the effluent TN, TP and NO3--N concentrations of MBR for varying recirculation configurations. Varying the SRT in the MBR impacted nutrient removal with 77.9% TN and 70.3% TP removal for 25 days SRT, 80.6% TN and 75.5% TP removal for 50 days SRT, and 84.8% TN and 61.5% TP removal for 75 days SRT. BiowinRTM modeling showed that the anoxic heterotrophic yield, oxic endogenous decay rate, anoxic hydrolysis factor, anaerobic hydrolysis factor, and fermentation rate increased proportionally with SRT. The estimated microbial kinetic parameters from BiowinRTM modeling for various SRTs predicted the experimental effluent quality at an SRT of 35 days. Incorporation of anaerobic, anoxic, and oxic sequences with intermittent aeration into the cycles of a full-scale sequencing batch reactor system (SBR) resulted in improvement in biological nutrient removal for the treatment of municipal wastewater and wastewater from a salad dressing plant. The two modified SBR schemes tested provided excellent sCOD removal (93--98%), TN removal (84--90%) and TP removal (86--88%) in comparison to the regular SBR scheme which gave 55% TN removal and 45% TP removal. Winter temperatures impacted TN and TP removal negatively but did not impact sCOD and NH3-N removal.</p>