Using surrogates to improve plant performance

This article presents the results of a study designed to evaluate the use o f pathogen surrogates as a tool in treatment optimization and to predict pa thogen occurrence. A comprehensive matrix was developed to relate water qua lity and process variables for 24 potable water sources and 12 possible sur rogates to the target pathogens of Giardia, Cryptosporidium, and enteric vi ruses. No "ideal" surrogate for predicting occurrence of protozoan pathogen s or treatment performance was identified because of analytical constraints and low pathogen occurrence. However, it was concluded that aerobic spores and particle counts could be used as surrogate measures to evaluate or imp rove treatment plant performance. Utilities should select not one but a num ber of surrogates to assess raw water quality and treatment plant performan ce.