An A2O-MBR system for simultaneous nitrogen and phosphorus removal from brewery wastewater

Abstract

Anaerobic/Anoxic/Oxic – Membrane BioReactor (A₂O-MBR) system was used to enhance simultaneous removal of nitrogen and phosphorus from brewery wastewater. The A₂O unit containing microorganisms with short solids retention time (SRT) was employed mainly for removal of organic matter and phosphorus together with denitrification. The MBR containing microorganisms with long SRT was employed mainly for nitrification of NH4⁺-N and recirculation of NO₃^--N. The model of A₂O-MBR system made from polyacrylic with the capacity of 49.5 liters was operated with hydraulic retention times decreased from 24, 18 to 12 hours corresponding to organic loading rates increased from 0.50, 0.75 to 1.00 kg COD/m³.day. The results showed that the model not only treated organic matter well but also nearly completely removed both nitrogen and phosphorus. For all three loading rates, chemical oxygen demand (COD) concentration decreased significantly in the anaerobic and anoxic compartments of the A₂O unit, indicating that most of organic matter was utilized in the anaerobic and anoxic compartments for phosphorus release and denitrification, respectively. Nitrification in the MBR was almost perfectly completed, with average NH4 ⁺-N removal efficiencies of over 98%. Denitrification in the anoxic compartment happened as much as possible. Demands for the development of PAOs, which were responsible for enhanced biological phosphorus removal (EBPR) processes, could be provided. For loading rate of 0.75 kg COD/m³.day, treatment efficiencies of COD, NH₄⁺-N, total nitrogen (TN) and total phosphorus (TP) of the model were the highest as 95.4, 99.2, 86.7 and 84.6%, respectively. Output values of these parameters were within the limits of Vietnam National Technical Regulation on Industrial Wastewater (QCVN 40:2011/BTNMT), column A. The model of A2O-MBR system was capable of achieving effluents with very low nitrogen and phosphorus concentrations from brewery wastewater.