Publication Summary

A one-year survey of effluent metal concentrations and associated general chemistry parameters was conducted on four wastewater treatment plants (WWTPs) and their receiving waters, all located within the Puyallup River drainage basin. The facilities include: the Orting WWTP on the lower Carbonado River, the Buckley WWTP on the White River, the Wilkeson WWTP on Wilkeson Creek, and the Carbonado WWTP on the upper Carbonado. Samples were take bimonthly at the Orting and Buckley facilities, and once every four months at the Wilkeson and Carbonado facilities.

A one-year survey of effluent metal concentrations and associated general chemistry parameters was conducted on four wastewater treatment plants (WWTPs) and their receiving waters, all located within the Puyallup River drainage basin. The facilities include: the Orting WWTP on the lower Carbonado River, the Buckley WWTP on the White River, the Wilkeson WWTP on Wilkeson Creek, and the Carbonado WWTP on the upper Carbonado. Samples were take bimonthly at the Orting and Buckley facilities, and once every four months at the Wilkeson and Carbonado facilities.

Statistical analysis of parameter data sets indicates that copper and zinc concentrations were associated with total suspended solids (TSS) concentrations, and reducing TSS may be a means of controlling metal loads to the receiving water. Orting, Buckley, and Wilkeson 24-hour sample effluent TSS loads were greater than NPDES permitted monthly average limits during one or more sampling events. Buckley exceeded the permit instantaneous peak flow for two events. Orting, Buckley, and Wilkeson flows were greater than the NPDES permitted maximum monthly average influent flow limit during one or more sampling events. With the exception of Buckley′s May 1996 dry weather flow, these excursions occurred during extreme flood events. Most effluent metal concentrations were within both permit interim and final maximum daily limits, with a few exceptions. The Buckley February 1996 effluent mercury concentration exceeded both the permitted interim and final maximum daily limit. The Carbonado effluent copper concentrations exceeded the final maximum daily limits during all sampling events.

Buckley and Wilkeson effluent concentrations for copper at the edge of the acute dilution zone boundary were found to have exceeded water quality criteria during a number of individual sampling events. The Buckley mercury concentration at the edge of the chronic dilution zone boundary exceeded water quality criteria during the February and March 1996 sample events. It was recommended that the facilities take steps to control effluent TSS loads, high influent flows, and effluent metal concentrations, particularly by reducing inflow and infiltration into their respective collection systems. Changes to the permit metals limits may be needed to reflect the lower receiving water hardnesses detected during the inspection.