ABSTRACT
It is common practice to use the 45μm membrane filter index, MFI, to estimate the clogging potential of water that has to be infiltrated using recharge wells (Olsthoorn 1982). However, a quantitative relation between clogging rate and MFI was not available. Pyne (1995) shows that the hydraulic conductivity of the aquifer has an influence on the clogging rate, but this influence is also not quantified. Published data and new experiments show that the MFI that is measured for a certain water type, depends on the square of the pore size of the filter that is used to measure the MFI. The pore size of the porous medium where water is infiltrated in, can be estimated from grain-size distributions and is related to the hydraulic conductivity of the medium. When the quadratic relation between MFI and pore size is taken into account, the theoretical relation between MFI and clogging rate as published by Olsthoorn (1982) yields values that are close to actual field measurements. Predicted clogging rates using this new theoretical relation are compared to measured rates in recharge wells used for aquifer thermal-energy storage and are also compared to measured clogging rates in ASR wells as published by Pyne (1995). Both datasets show that the clogging rates of these wells can be predicted satisfactorily, especially considering the uncertainties in measured parameters like MFI and hydraulic conductivity.
