AWWA JAW59539

Until recently, not much was known about Cryptosporidium removal by filtration during nonideal operating periods. With the exception of formalin-inactivated oocysts, no reliable, quantitative surrogates for live oocysts have been demonstrated for a variety of operational conditions and filtration regimes. In this article, the authors demonstrate that oocyst-sized microspheres may be a useful tool for demonstrating and quantifying conventional and inline filter performance when data are available over a wide range of oocyst and microsphere removals. Oocyst-sized microspheres are easier, safer, and less expensive to work with than Cryptosporidium. In addition, this approach may be useful to utility managers in assigning log removal credits for regulatory purposes. This work provides an approach for determining a realizable, quantitative surrogate relationship between oocysts and oocyst-sized microsphere removals by filtration. The article also emphasizes that, to be accurate, process evaluations must consider all operating periods, not just optimized operation. Includes 22 references, tables, figures.