Riverbank Filtration for IESWTR Compliance

Abstract

The Central Wyoming Regional Water System operates 29 groundwater collection devices in an alluvial aquifer adjacent to the North Platte River. These collection devices were previously designated "groundwater under the direct influence of surface water." In lieu of constructing a conventional surface water treatment plant, the utility opted to perform a two-year study to demonstrate that riverbank filtration (i.e., natural filtration) provided the 2.0-log reduction of Cryptosporidium required under the Interim Enhanced Surface Water Treatment Rule (e.g., riverbank filtration is the primary filtration process). Using multiple surrogates of various sizes encompassing those of Giardia and Cryptosporidium, the utility demonstrated 2.0-log reductions in more than 90% of matched data pairs. No Giardia cysts or Cryptosporidium oocysts were found in any of the 170 groundwater samples. This level of removal was achieved during the summer months when infiltration rates are high because of increased river stage and well-field production.he Central Wyoming Regional Water System (CWRWS) uses the North Platte River alluvial aquifer as its primary source of drinking water. The utility operates 29 collection devices that provide 85% of the public water to the city of Casper and its surrounding communities. Specifically, the utility operates 25 vertical wells, with individual well capacity ranging from 0.5 to 1.0 mgd (1.9 to 3.8 ML/d); three horizontal (caisson) collector wells, each producing ~2.0 mgd (~7.6 ML/d); and one infiltration gallery, producing ~4.0 mgd (~15.1 ML/d). Maximum production from the well field is estimated to be 25 mgd (95 ML/d). The collection devices are scattered over 5 sq mi (13 km 2 ) in the Caspar and Morad well fields located on both sides of an oxbow adjacent to the North Platte River (Figure 1). Recharge to the aquifer is provided by the river and is supplemented to many of the collection devices T filtration 2005

Cryptosporidium spp. and Giardia spp. removal by bank filtration at Beberibe River, Brazil

“…Gollnitz, Clancy, Mcewen, and Garner () also provided evidence that BF is effective in removing Cryptosporidium oocysts in BF systems located on the Ohio and Wyoming rivers.…”

A Modeling Framework for the Design of Collector Wells

“…Source water for the Saylorville collector wells will be a mixture of upgradient groundwater and induced recharge from the Des Moines River. The natural filtration that occurs in RBF systems provides effective pretreatment for pathogens and other undesirable surface water constituents (Gollnitz et al 2003, 2004, 2005). Compared to groundwater, surface water is generally lower in hardness, total dissolved solids, alkalinity, dissolved iron, and dissolved manganese concentrations.…”

The impact of storm events on a riverbed system and its hydraulic conductivity at a site of induced infiltration

“…RBF has been highly effective in filtering out particles, bacteria, viruses, and parasites (Kuehn, 2000). Gollnitz et al (2005), for example, found that for a system in Wyoming, RBF resulted in up to 4.0 log (99.99%) reduction in algae and diatoms and at least 2.0 log (99%) reduction in both Giardia and Cryptosporidium surrogates (no Giardia or Cryptosporidium were found in the samples).…”

“…Substantial treatment of RBF-derived water is still required to potentially remove, kill, or inactivate Cryptosporidium. Public water utilities can demonstrate on a case-by-case basis the efficacy of their RBF systems in removing these pathogens, but this option has had limited application (Gollnitz et al, 2005) because of the length and cost associated with RBF studies.…”