A new ASTM test method serves as an important option in determining the potential of particulate matter to cause fouling in pressure-driven membrane processes used in water treatment.
ASTM members say that this new alternative (soon to be published as D8002, Test Method for Modified Fouling Index (MFI-0.45) of Water) will help end the struggle to entirely change an existing test method (D4189, Test Method for Silt Density Index (SDI) of Water) by providing a separate standard to cover MFI.
“The addition of a new method will provide the water industry with a much needed supplemental test method,” says Steve Duranceau, Ph.D., P.E., associate professor at the University of Central Florida in Orlando. “It allows for ASTM to support both SDI and MFI testing methods.”
The MFI is a promising alternative to SDI because it is based on the cake filtration model and can be corrected for pressure and temperature. The new test method is applicable to low and high turbidity feed waters. The MFI has been developed over the past 25 years and is used in Europe.
Subcommittee D19.08 on Membranes and Ion Exchange Materials developed the standard to help counteract the impact of particulate fouling, which has plagued reverse osmosis systems since their first use in desalination. This remains a persistent issue today for reverse osmosis and other pressure-driven processes such as microfiltration, ultrafiltration and nanofiltration.