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Various studies have shown that three factors - filter media, temperature, and the presence of chlorine in the backwash water - affect the performance of drinking water biofilters. However, the effects of these factors and the potentially significant interactions among them have not been compared quantitatively in previous studies. In particular, there is very limited information available on the performance of biofilters at low temperature (5 degrees C). In this bench-scale study of biological filtration, the authors found that media (anthracite versus granular activated carbon [GAC]), temperature, and the presence/absence of chlorine in the backwash water were all important factors affecting the removal of biodegradable organic matter (BOM). However, a substantial impairment of performance was only seen when all factors were at their most unfavorable settings. The combination of chlorine and low temperature had only a minor effect on GAC filters. Chloramine in the backwash water did not substantially affect BOM removal at either high or low temperature. In general, a period of 20 to 40 days was required for the biofilters operated at the high temperature (20 degrees C) to reach constant removal of the most easily biodegradable compounds. The results of this study show that biofilters can perform well at low temperatures in removing easily biodegradable compounds, such as many ozonation byproducts. At 5 degrees C., GAC filters were slightly affected by chlorine in the backwash water. However, chlorinated backwash water is detrimental to the results obtained when anthracite filters are operated at this low temperature. Includes 38 references, tables, figures.

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Edition: Vol. 93 - No. 12 Published: 12/01/2001 Number of Pages: 12 File Size: 1 file , 480 KB