Large-Scale Membrane Feasibility Study

Water Research Foundation and City of Kansas City, 
Missouri

Large-Scale Membrane Feasibility Study

Service Type: 
Project Highlights: 
  • Evaluation of retrofit of KCMW SD 240 - mgd lime softening and granular media filtration plant with membrane filtration.
  • Demonstrated feasibility of membrane filtr ation at driving heads equal to t hose used in granular media filtration.
  • Extremely cost-effective alternative for me mbrane applications.
Carollo's custom membrane pilot unit.
Carollo's custom membrane pilot unit was instrumental in KCMWSD's large-scale membrane feasibility study. The unit's design allows it to be equipped with membrane modules from various manufacturers.

Under the Water Research Foundation Tailored Collaboration Program, Carollo investigated the feasibility of a large-scale membrane retrofit of the Kansas City, Missouri, Water Services Department’s (KCMWSD) 240-mgd lime softening and filtration facility. The goal of the study was to use KCMWSD as a case study to document issues associated with retrofitting membrane filtration into granular media filtration facilities greater than 50 mgd.

The retrofit evaluation focused on three specific retrofit strategies that included submerged, proprietary pressure-driven, and custom-designed membrane systems. Carollo tested an inside-to-outside (I/O) pressure driven membrane system; a custom-designed, outside-to -inside (O/I) pressure-driven membrane; and a vacuum-driven immersed membrane system at the KCMWSD plant. The I/O membrane featured high permeability and a similarity of operating characteristics to other I/O systems, offering the potential for competitive bidding of replacement modules. The custom- designed O/I membrane featured operation simplicity, as well as a high fiber packing density and active membrane surface area per module, making it amenable to low flux applications. The immersed membrane system featured high fiber packing density as well as potential operation within the existing upstream hydraulic grade line.

Following the pilot study, Carollo developed conceptual membrane system layouts to maintain water production and to fit within the limits of the existing filter gallery. Carollo investigated two different retrofit strategies for the pressure-driven membrane systems. These included operating the membrane process within the existing upstream hydraulic grade line (eliminating the need for feed pumps) and a pumped feed water configuration. Both options proved feasible for the custom- designed O/I membrane, while only a higher flux, pumped feed water configuration was viable for the I/O membrane. Lower flux, gravity-driven filtration of the I/O system was not feasible due to site footprint constraints. In parallel, Carollo reviewed the retrofit strategy for the submerged system. To further reduce costs and minimize the system footprint, Carollo evaluated using the highservice pumps currently in used for backwashing the granular media filters as membrane backwash pumps, and utilizing the existing waste washwater handling infrastructure.

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