Enhancement of the membrane filtration index (MR) method for determining the clogging potential of turbid urban stormwater and reclaimed water used for aquifer storage and recovery

Well clogging is a potential impediment to the use of aquifer storage and recovery (ASR) wells. With filtration of suspended solids the most frequently reported form of clogging, methods to predict its impact serve as useful management tools. In this study, the Membrane Filtration Index (MFI), a standard test of the rate at which water clogs a membrane filter, has been extended for use with turbid and organic-rich waters, and to improve precision of MFI for all water qualities. Waters from 12 sites, including mains, urban stormwater and reclaimed water, which are or have the potential to be water sources for aquifer storage and recovery (ASR) in southern Australia, were analyzed for MFI, turbidity, total suspended solids, total organic carbon, particle size and SEM. Time-series data were collected at two of these focus sites over a 12-month period. The upgraded MFI apparatus was found to give repeatable results with coefficients of variation generally less than 10% for MFIs of up to 900 s/L-2. This extends the range of utility of the apparatus from previously reported limits of < 100 s/L-2. Little more than half the variance in MFI could be explained with the measured water quality parameters, which implies that MFI cannot be reliably predicted from these. We attribute this to the complex nature of the inorganic and organic particles present in the waters. A field study is currently underway to relate MFI to well clogging at one of the focus sites.