AWWA JAW59117

Many well fields in sand and gravel aquifers are likely to be hydraulically influenced by surface water; however, their risk for Giardia and Cryptosporidium contamination may be low because of natural filtration (i.e., riverbank filtration [RBF]). This study was undertaken to evaluate the true risk for pathogenic protozoa in a well field being recharged by a local river. The authors assert that RBF should be considered as a treatment process, with the proper amount of assigned treatment credit. It is one of many treatment tools in the microbial toolbox in the proposed Long Term 2 Enhanced Surface Water Treatment Rule, but it should be given more than the 1.0 log credit if warranted (demonstrated) at a particular well field. It is hoped this information will help utility managers obtain the proper amount of treatment credit for RBF, especially if their groundwater source is designated as being "under the direct influence of surface water." Includes 20 references, tables, figures.