Development of a framework for quantifying the removal of humic substances by biological filtration

Biological filtration is finding increasing use in the treatment of drinking water and is one process that is used to remove humic substances. It would be extremely useful to have a framework to quantify such removals as a function of substrate and operating parameters. This paper explores the use of biofilter dimensionless contact time, X*, to provide such quantification. X* incorporates reactor contact time and surface area, as well as substrate diffusivity and biodegradation kinetic parameters. Removals of biodegradable organic matter increase with increasing X*, but in a less than proportional way. investigations reported in the literature have shown very limited biodegradation of unozonated humic substances under water treatment conditions. Following ozonation much greater removals are reported, This can be attributed to the increase in diffusivity and biodegradability due to ozonation, which leads to a substantial increase in X* for a given filter. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.