Although it has been nearly 200 years since the first known granular media filtration was used for potable water treatment, this Victorian era technology remains as perhaps the most important step in multi-barrier treatment of drinking water for the vast majority of the world. Despite this widely recognized importance of granular media filtration, we know surprisingly little about the characteristics of particles that enter and subsequently pass through these filters. The inadequacy of existing turbidimeters in detecting variations of organic and inorganic material in the submicron size groups may potentially limit the degree of optimization that can be practiced in daily operations of facilities. Material in the ultrafine fraction and its poor removal by the filters, as well as their generation within the filter media, suggests further optimization of filter operation as well as pretreatment upstream is possible and needs further investigation.


Results from this study indicate that better removal of organic material may improve performance of filters. The effect of pre-oxidation on filter performance with respect to larger particles in the effluent should be evaluated carefully by utilities.