ABSTRACT
The overall objective of this paper is to characterize natural organic matter (NOM) removals by biologically active sand filters. Specific goals are to ascertain pretreatment effects, i.e., coagulation and ozonation, on NOM biodegradability and chlorine reactivity. Emphasis will be given to evaluating the influence of location within a conventional treatment process train on biofilter efficiency and to examine NOM removal mechanisms associated with biofiltration, especially with aged sand media.
As expected, preozonation enhances biofiltration removals of source water NOM. However, precoagulation reduces biofiltration efficiency and the positive treatment influence of preozonation on biofiltration performance. Alum coagulation removes significant quantities of higher molecular weight, hydrophobic fractions of NOM which are also susceptible to biofiltration removal. Finally, sand coating metal composition, which is generally associated with the age of the filter media, may have an impact on biofiltration removal of NOM.
