Adsorption and Biodegradation in Biological Activated Carbon Treatment of Drinking Water

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In 1992, adsorption and biodegradation of organics in biological activated carbon(BAC)column were investigated by the moment analysis of the pulse response and the following was concluded.(i)The biodegradation rate of easily-biodegradable substances is independent of the biofilm support.(ii)The biodegradation rate of total organics is also independent of the biofilm support, although the faster rates were observed when the activated carbon is used for the biofilm support due to the existence of irreversibly-adsorbing substances.(iii)The adsorption capacity is significantly reduced by competitive adsorption of biodegradation products. It can be said that this approach is useful for measuring the adsorption properties and the bacterial activities in BAC separately.In 1993, the behavior of trihalomethane precursors met in BAC treatment was investigated and the following was concluded.(i)In BAC treatments, trihalomethane precursors included in raw water can be adsorbed and biodegraded, and also simultaneously fresh precursors can be generated by bacterial activities as metabolic products and autolysis products. Especially, the control of the latter precursor is crucial when applying BAC to drinking water treatment.(ii)A part of autolysis products of bacteria is non-biodegradable and easily adsorbed onto activated carbons. The trihalomethane formation potential in BAC treatment water is controlled by the behavior of this particular substances. A mathematical model describing the behavior of various trihalomethane precursors was proposed and successfully simulated the experimental results.The further investigations may include the so-called bioregeneration of the substances above mentioned. By introducing the kinetics of such bioregeneration into the present mathematical model, it can be a useful tool for designing and operating BAC for drinking water treatment on scientific basis.