COSEE Ocean Systems: News
A View from Above: Wastewater Diversion Plumes in Southern California (October, 2014)
Description: The Southern California Bight (SCB) is an ecologically important marine habitat and a valuable resource in terms of commercial fishing and recreation. With a census of over 17 million people, potential impacts of such a large population are cause for concern on coastline water quality. Los Angeles and Orange Counties are home to two of the largest wastewater treatment plants along the U.S. West Coast (Figure 1). The Hyperion Treatment Plant (HTP) and the Orange County Sanitation District (OCSD) discharge secondary-treated wastewater, or effluent, into the SCB from outfall pipes that terminate five miles offshore at a depth of about 60 meters to limit risks to the marine environment and human health (Figure 1, black lines). Treated effluent contains contaminants including oils, various chemicals and metals, and nutrients. The effluent disperses and sufficiently mixes with deeper ambient waters remaining trapped at depth under typical density-stratified conditions; however, on occasion during periods of reduced stratification (September-December timeframe in the SCB) the submerged buoyant plumes can surface. When scheduled or emergency maintenance on the normal outfall system is necessary, effluent is diverted to shorter outfall pipes that terminate one mile offshore at shallower depths (i.e., approximately 20m) (Figure 1, red lines). Such temporary release of wastewater in nearshore environments increases the risk to human health, water quality, and coastal ecosystems, especially in times of reduced water column stratification. Two such SCB diversions include the 2006 HTP (28-30 November 2006) and 2012 OCSD (11 September - 3 October 2012) diversions. During both diversions, extensive in situ and satellite data were collected to detect the wastewater plume and assess its impact on nearshore water quality. Here researchers examine the results from satellite data. [Source: NASA Jet Propulsion Laboratory]
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Source: NASA Jet Propulsion Laboratory
Publish Date: 10/22/2014
Reading Level: Basic
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