AWWA JAW18744

This article discusses a series of aeration studies conducted to assess the effectiveness of packed column and diffused aeration as a treatment and control technology for trihalomethanes in water. Results indicate that total trihalomethane (TTHM) removals of >95 percent can be achieved in a packed column irrespective of the initial concentration, provided that sufficient packing depth and air are available. The effectiveness of the packed column is dependent on water temperature, packing medium, surface loading rate of the water, depth of packing, and the air to water ratio. Performance was not related to the concentration of contaminant (chloroform) or to the water source. Concentrations of contaminant in the effluent from a packed column can thus be estimated from the concentration of the organic in the water source. Theoretical predictions for chloroform removal overestimated actual packed column aeration efficiency. Pilot scale packed column studies provided conceptual design data and were useful for optimizing operational conditions and choosing cost effective designs. Data obtained for pilot columns were representative of the performance of larger full scale systems as demonstrated by results for a 6-inch compared with a 15-inch column. Diffused aeration was less effective than packed column aeration for the reduction of TTHMs in a water source with a high precursor concentration. A longer detention time is deleterious when the rate of THM formation equals or exceeds the rate at which THMs are stripped from the water. Diffused aeration improved with increased water depths and air-to-water ratios. Distribution of air along a channel was not an advantage over a single air source. Performance was related more to the volume of air applied than how it was applied. Includes 8 references, tables, figures.