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Evaluation of membrane bioreactor process capabilities to meet stringent effluent nutrient discharge requirements
Edwin J Fleischer1, Thomas A Broderick, Glen T Daigger
1CH2M HILL, Herndon, Virginia 20171, USA.
Summary
A six-stage membrane bioreactor (MBR) pilot plant effectively removed nutrients, achieving low effluent total nitrogen (<3 mg/L) and total phosphate (<0.1 mg/L) concentrations for Chesapeake Bay goals. This process offers valuable insights for designing MBRs for nutrient reduction.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Wastewater Management
Background:
- Nutrient pollution, particularly nitrogen and phosphorus, poses a significant threat to aquatic ecosystems like the Chesapeake Bay.
- Conventional wastewater treatment methods often struggle to meet stringent nutrient reduction targets.
- Membrane bioreactors (MBRs) offer a promising alternative for advanced wastewater treatment and nutrient removal.
Purpose of the Study:
- To evaluate the performance of a six-stage membrane bioreactor (MBR) pilot plant for producing low-nutrient effluent.
- To demonstrate the MBR's capability to meet stringent nutrient reduction goals, specifically for the Chesapeake Bay.
- To assess the effectiveness of biological and chemical nutrient removal strategies within the MBR system.
Main Methods:
- Operation of a six-stage MBR pilot plant with specific anoxic and aerobic zones for biological nutrient removal.
- Inclusion of methanol as a carbon source in a downstream anoxic zone to enhance nitrogen removal.
- Combination of biological (anaerobic zone) and chemical (alum addition) processes for phosphorus removal.
- Characterization of biological nutrient removal using the International Water Association Activated Sludge Model No. 2d.
Main Results:
- Reliable reduction of effluent total nitrogen to less than 3 mg/L.
- Consistent achievement of effluent total phosphate concentrations below 0.1 mg/L, with levels as low as 0.03 mg/L.
- Alum addition enhanced MBR sludge filtration characteristics and reduced membrane fouling.
- Aeration of membranes produced thickened sludge suitable for recycle to the main aeration zone, optimizing nutrient removal.
Conclusions:
- The six-stage MBR system reliably achieves very low effluent nutrient concentrations, meeting critical environmental goals.
- The MBR process demonstrates a robust and effective approach for advanced biological and chemical nutrient removal.
- Findings provide valuable design and operational insights for MBRs targeting stringent nutrient reduction in wastewater treatment.