Use of an integrated monitoring approach to determine site‐specific effluent metal limits

Abstract

An integrated monitoring approach was implemented for an overland-flow wastewater facility over a 1-year period to determine whether the effluent caused water quality impairment in the receiving system (X-Trib) and appropriate metal effluent limits. The Rapidan Service Authority (Gordonsville, Va.) wastewater effluent comprises approximately 98% of the X-Trib flow under 7Q10 conditions. Aquatic life in both X-Trib and South Anna River, downstream of the discharge, were previously recorded as heavily impacted prior to the addition of overland-flow treatment. Three forms of monitoring were implemented at this facility: chemical-specific analyses of effluent samples, whole effluent chronic toxicity tests, and stream bioassessments. Two reference streams in the area were also sampled to determine the types of fauna capable of inhabiting the receiving stream. Chemical data suggested elevated levels of copper, cadmium, and lead instream compared to U.S. EPA criteria and Virginia Standards. Chronic toxicity tests, however, often indicated no effects on sensitive EPA indicator species. Stream bioassessments suggested that both habitat and benthic substrate quality were limiting for aquatic biota in the X-Trib. Benthic grab samples and fish sampling suggested ecological impairment due to the effluent. However, introduced benthic substrate studies in the fall and spring indicated no impairment. Thus, the adverse impact observed in benthic samples appeared to be an historical effect of the effluent prior to upgrade, and not an indication of present effluent quality. The biological results indicated that the upgraded plant was in compliance with the goals of the Clean Water Act despite elevated metal levels. High effluent total organic carbon (TOC) was at least partly responsible for this result since even occasional high levels of dissolved metals did not cause toxicity. Our results suggest that following a truly integrated monitoring approach can yield appropriate effluent metal limits on a site-specific basis without necessarily relying on criteria or standards modification studies; state standards for metals, even based on the dissolved fraction, may, in some cases, be overly stringent where other factors are present that reduce the bioavailability of those metals; and setting appropriate standards for effluent-dominated streams requires consideration of effluent characteristics which may affect the bioavailability of pollutants. Water Environ. Res., 66, 733 (1994).

Evaluation of the water‐effect ratio procedure for metals in a riverine system

“…Current WER procedures alone may not be capable of adequately addressing the complexity that results when more than one metal is of concern at the site, either due to the wastewater effluent or to upstream water quality conditions, or both. In these cases, a more integrated laboratory and field approach may be necessary [2].…”

“…With the increased availability of toxicity test data generated by waste water dischargers under the Clean Water Act, it has become apparent that many effluents and surface waters may contain higher concentrations of certain heavy metals (even as dissolved metal) than suggested by U.S. Environmental Protection Agency (EPA) criteria and yet be nontoxic to recommended, sensitive test species [1,2]. These findings, along with recent research on the aquatic chemistry and fate of various heavy metals [3–6], has lead to increased discussions on the appropriate way to measure and regulate the toxic fraction of metal in a given aquatic matrix.…”

Influence of Drought and Municipal Sewage Effluents on the Baseflow Water Chemistry of an Upper Piedmont River

“…Rivers and streams dominated by WWTP effluents are typically located in certain western states in the United States (U.S.) (Berestov, Fernando, & Fox, 1998;Brooks et al, 2004;McMahon, Tindall, Collins, Lull, & Nuttle, 1995;Reilly, Horne, & Miller, 2000;Saunders & Lewis, 2003) and in other arid or semi-arid climate regions around the world (Deksissa, Ashton, & Vanrolleghem, 2003;Marti et al, 2004). Because such rivers and streams are less common in the eastern U.S., however, fewer studies of WWTP effluent effects on downstream hydrology and water chemistry have been conducted in eastern U.S. states (Andersen et al, 2004;Diamond, Hall, Pattie, & Gruber, 1994). Recently, Andersen et al (2004) described the effects of WWTP effluent discharges on the water chemistry and nutrient concentrations in the Bush River, South Carolina (SC).…”

Evaluation of the Water-Effect Ratio Procedure for Metals in a Riverine System

“…With the increased availability of toxicity test data generated by waste water dischargers under the Clean Water Act, it has become apparent that many effluents and surface waters may contain higher concentrations of certain heavy metals (even as dissolved metal) than suggested by U.S. Environmental Protection Agency (EPA) criteria and yet be nontoxic to recommended, sensitive test species [1,2]. These findings, along with recent research on the aquatic chemistry and fate of various heavy metals [3][4][5][6], has lead to increased discussions on the appropriate way to measure and regulate the toxic fraction of metal in a given aquatic matrix.…”