The Ohio Water Resources Center at The Ohio State University formed a partnership with Ohio EPA and the to create a framework for developing design criteria for emerging technologies that would allow them to be adopted for use by Ohio EPA as a supplement to TSS. With this framework, we developed design criteria for Low Pressure Membrane (LPM) Filtration, an established treatment technology with over 280 U.S. installations.
To develop design criteria for LPM filtration, we identified water quality and operational components critical to predicting and maintaining water production capacity. A core advisory committee was formed of water regulators, water utility professionals, design engineers, and membrane experts. Subcommittees composed of these professionals were established to conduct iterative, round table discussions during each step of the design criteria development process. Operating flux was identified as a critical design parameter for calculating design capacity and as a component of membrane fouling. Fouling is an expected part of membrane operation and is controlled with appropriate pretreatment and maintenance. A critical concern of providing LPM filtration design criteria was that premature irreversible fouling, defined as fouling that decreases flux capacity below its design value prior to the end of the membrane’s expected design life, should be minimized
Factors identified to impact fouling potential were membrane feed water quality and membrane product characteristics. Membrane feed water quality parameters that indicate fouling potential were turbidity, total organic carbon, dissolved iron, and dissolved manganese. We sent a technical request for information to LPM manufacturers to obtain product-specific flux values for two water quality bins (good and medium) based on the four feed water quality parameters. Water quality outside these limits was defined as poor and will still require a pilot-scale demonstration study for Ohio EPA Plan Approval. The product-specific flux values for good and medium water quality were validated by the Ohio Water Resources Center. The validation data came from existing studies for each product that included membrane feed water quality, flux, transmembrane pressure, cleaning frequency, and duration of the study. These product-specific flux values for the two water quality bins were the heart of the design criteria provided to Ohio EPA.
These design criteria are currently being reviewed by Ohio EPA for adoption. Once adopted, they will allow a PWS to gain Ohio EPA Plan Approval for surface water LPM filtration without the currently required pilot-scale demonstration study. This is accomplished by providing product-specific flux values for two defined membrane feed water quality limits at which a PWS can receive Plan Approval for a proposed LPM filtration improvement. Manufacturers whose product-specific flux value and validation data is accepted into these design criteria by Ohio EPA will be able to respond to a PWS’s pre-selection bid document prior to detail design without having to conduct a pilot-scale demonstration study. This pre-selection bid document for an actual project will most likely contain additional performance requirements (e.g., capital and O&M costs, energy usage, etc.) from the individual PWS in addition to meeting the Ohio EPA requirements. Ohio EPA intends to adopt the design criteria for LPM filtration as a supplement to the TSS. The framework created here to develop design criteria for an emerging technology is to be implemented by the Ohio Water Resources Center for subsequent emerging technologies.
