Carboxylic acids: formation and removal in full‐scale plants

Abstract

Carboxylic acids were formed upon ozonation but were not completely removed by biological filtration, which could have implications for bacterial regrowth in distribution systems.This article presents data on the formation and removal of carboxylic acids in a full‐scale treatment plant employing ozonation and biological filtration. Carboxylic acid concentrations increased after ozonation and decreased through subsequent filtration. Simple linear relationships between major water quality parameters (e.g., temperature, pH) and acid formation did not exist. Yields of carboxylic acids on ozonation were an order of magnitude greater than for the corresponding aldehyde. An empirical linear model could describe the removal of carboxylic acids through biological filtration from a practical point of view. However, the data suggest the removal mechanism may be complex. Although contact times in the filters were quite long (on the order of 30 min), removal of several carboxylic acids was incomplete (e.g., average effluent concentration of formate was 44 μg/L).