Peak flux performance and microbial removal by selected membrane bioreactor systems

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Membrane Bioreactor (MBR) Systems

Background:

• Wastewater treatment plants (WWTPs) face challenges in managing variable flow rates, especially peak flows.
• Membrane bioreactor (MBR) systems are increasingly adopted for their efficiency in producing high-quality effluent.
• Understanding MBR performance under peak flux conditions is crucial for optimizing operational strategies.

Purpose of the Study:

• To evaluate the operational and water quality performance of six MBR systems under average and peak flux conditions.
• To assess the impact of peak flux operation on membrane permeability and fouling.
• To determine the microbial removal efficiency, including MS-2 coliphage rejection, during peak flux.

Main Methods:

• A 18-month pilot study at Point Loma Wastewater Treatment Plant (PLWWTP) using six MBR systems.
• Systems were operated at peak flux (4 h/day for 6 consecutive days) to assess performance.
• Virus seeding studies with MS-2 coliphage were conducted during peak flux to evaluate rejection capabilities.

Main Results:

• MBR systems achieved excellent steady-state effluent quality (<2 mg/L BOD, <0.1 NTU turbidity).
• Peak flux operation resulted in a reversible 22-32% drop in permeability, increasing with MLSS concentration.
• MBR systems demonstrated high microbial removal (5.8-6.9 logs total coliforms, >5.5-6.0 logs fecal coliforms) and significant MS-2 coliphage removal (1.0-4.4 logs when seeded).

Conclusions:

• MBR systems can effectively manage peak flows for extended periods with moderate fouling.
• Submerged MBR permeability is sensitive to MLSS concentration during peak flux events.
• MBR systems provide robust microbial removal, though seeded MS-2 coliphage removal varied, possibly due to particle association.