The biological treatment especially by granular activatedcarbon (GAC) biofilter has been found effective in removing organicsubstances that can cause the microbial growth in the pipe lines,and is normally recommended to be included in the water treatmentprocesses after ozonation [Bouwer and Crowe, 1988; Hozalskiet al., 1995; Ahmad and Amirtharajah, 1998; Carlson and Amy,1998]. Bacterial masses attached onto the filter media as biofilmoxidize most of the organics and use it as an energy supply and carbonsource. Removal of the organic matters not only impairs microbialregrowth but also reduces taste and odor, the amount of organicprecursor (available to form disinfection by-products, corrosion potential)and other micropollutants of health and aesthetic concern.Because of its wide range of application, many studies have beendone on biofiltration system in last few decades (Table 1). However,theoretically it is still difficult to explain the behavior of a biofilter.The growth of different types of microorganisms in differentworking conditions makes it impossible to generalize the microbialactivities in a biofilter. The biofilters operated at different filtrationrates and influent characteristics can have diverse efficiency for differenttarget pollutants. Besides, due to some of the operational drawbacksof the biofilter such as performance fluctuation, maintenanceof biomass, and disinfection adequacy of the biofilter effluent, researchon biofiltration process has become imperative.
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