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| Un-ionized ammonia concentrations exceeded USEPA criteria for protection of aquatic life in Las Vegas Wash, Nevada, downstream from wastewater treatment plant discharges. Concentrations in all samples collected from April 1993 to April 1995 exceeded the criteria. The median ammonia concentration downstream from wastewater treatment plant discharges was more than 100 times the median value upstream from the discharges. Downstream ammonia concentrations decreased fivefold during 1996-97, following full implementation of tertiary treatment of wastewater, and USEPA criteria probably are no longer exceeded at this site. |
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