Article | April 4, 2014

Using Granular Activated Carbon To Meet DBP Regulations

The Roche Harbor Water Treatment Plant is located on the northwest side of San Juan Island in San Juan County, Washington state. Although a significant part of the land in the county is privately owned, the watersheds there provide a public benefit for both residents and visitors.  San Juan Island’s economy is tourist-driven; the island was voted #2 on the New York Times list of “41 Places to go in 2011.” Its marina has been a top boating destination for more than fifty years. Incorporated in 1886, the community has seen slow but steady population growth in recent decades. Roche Harbor Water System Inc. has been in operation since 1968 when PVC piping replaced the island’s existing wooden pipe system.

Roche Harbor serves approximately 500 homes and one resort. The facility’s capacity is rated at 0.5 million gallons per day (MGD), but is normally operated at 0.3 MGD. The Washington Department of Heath regulates the area’s drinking water. The plant draws its water from Briggs Lake, a small surface impoundment. High color and total organic carbon (TOC) were water filtration challenges associated with the lake water source. Suspended matter – comprised of a wide variety of organic particles such as zooplankton, algal cells, threadlike organisms, and bacterial cells combine – leads to high TOC. Roche Harbor’s filtered water had high levels of tastes and odors that generated numerous customer complaints.