MABR performance requirements drove a design basis for flows and loads as well as final effluent limits. A highlevel nitrogen balance was performed to estimate tank process effluent NH3-N reduction that would be necessary to ensure final effluent limits were maintained. The nitrogen mass balance considered raw sewage loading, biomass assimilation, and final effluent NH3-N limits, and assumed a worst-case scenario with non-nitrifying activated sludge process during winter operation. Calculations suggest MABR tank process effluent NH3-N must be less than 12 mg/L as monthly average to ensure final effluent NH3-N limits are maintained. Therefore, MABR tank effluent NH3-N < 12 mg/L as monthly average was specified for all operating conditions. Design elements of the final MABR system include: • An inlet valve chamber to allow flow control of MABR bypass of raw sewage and/or return activated sludge. • Influent flow splitter box with jet mixing and nozzles extending into blank cassette spaces. • Four parallel MABR tanks, each containing nine ZeeLung cassettes and two blank spaces to allow future cassette integration. • Hydraulic provision to raise cassettes 600 mm should internal cassette MLSS mixing prove inadequate. • On-line instrumentation (flowmeters & analyzers) to facilitate commissioning, research, testing and confirm MABR performance. EMBRACING A NEW APPROACH Through their willingness to break with conventional methods and investigate an alternative technology for secondary treatment, the Region of Waterloo was able to fully understand the unique value proposition of incorporating MABR technology at the Hespeler WWTP. The findings of the MABR study and feasibility assessment demonstrated that the upgrade would significantly improve effluent quality while reducing the plant’s energy consumption. Importantly, the Region of Waterloo’s conceptual design also established that the MABR system could be built and www.esemag.com @ESEMAG
installed at a lower capital cost, both now and when the plant is expanded in the future. Additionally, the compact footprint of the MABR design preserves space at the plant and the modularity of the technology allows the Region to pace its investment at the Hespeler WWTP in terms of meeting future capacity needs. The MABR system is currently under
construction and will be operational by the end of 2021. Jeff Peeters is with SUEZ Water Technologies & Solutions. Email: jeff.peeters@suez.com Olav Natvik is with Stantec Consulting Ltd. Email: olav.natvik@stantec.com
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