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.
Highlights
Vietnamese people consumed nearly 4.1 billion liters of beer in 2017
Anaerobic/Anoxic/Oxic (A2O) process commonly used in wastewater treatment is able to remove organic matter together with nitrogen and phosphorus with its own inherent advantages such as short hydraulic retention time (HRT), high pollutant removal efficiency and good shock loading capacity [5,6]
The process consists of three anaerobic, anoxic, oxic compartments and one settling tank which are arranged in sequence with nitrate circulating flow from the oxic compartment to the anoxic compartment and sludge circulating flow from the settling tank to the anaerobic compartment
Summary
The polyacrylic model of A2O-MBR system included Anaerobic/Anoxic/Oxic unit having an approximate dimension of 480 mm L x 150 mm W x 600 mm H with the corresponding working volume of 36.0 liters which was divided by baffles to create three compartments (anaerobic, anoxic, oxic) in ratio of 2:4:2 11 and MBR having an approximate dimension of 180 mm L x 150 mm W x 600 mm H with the corresponding working volume of 13.5 liters. 1/Wastewater tank: 200 liters (PE, Vietnam); 2/Anaerobic/Anoxic/Oxic unit with three compartments: 36.0 liters (Polyacrylic, Vietnam); 3/Settling tank: 7.2 liters (Polyacrylic, Vietnam); 4/MBR with a polyethylene hollow-fiber membrane module: 13.5 liters (Polyacrylic, Vietnam); 5/Middle tank: 50 liters (PE, Vietnam); 6/Feed pump: 11 liters/hour (Sandur, India); 7/Effluent pump: 16 liters/hour (Sandur, India); 8/Suction pump: 11 liters/hour (Blue & White, United State); 9/Sludge pump: 11 liters/hour (Sandur, India); 10/Paddle mixer 1: (IWAKI, Japan); 11/Paddle mixer 2: (IWAKI, Japan); 12/Blower 1: 38 liters/min (RESUN, Ap 001, China); 13/Blower 2: 38 liters/min (RESUN, Ap 001, China); 14/Sludge valve 1: ∅13 (Copper, Vietnam); 15/Sludge valve 2: ∅13 (Copper, Vietnam). Seed sludge was light brown, well-settled with sludge volume index of 98 and MLVSS/MLSS ratio of 0.74
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