Acute and Chronic Toxicity Testing of Drinking Water Treatment Residuals in Freshwater Systems

Abstract

The beneficial use of drinking water treatment residuals (DWTRs) faces barriers due primarily to uncertainties and concerns about their potential environmental impacts. We used total and water leachable toxic metal concentrations and 2 benthic organism-based bioassays to identify suitable DWTR substrates for introduction to freshwater systems. Using total metal contents and the consensus probable effect concentration concept, 3 DWTRs were selected and used in elutriate and toxicity studies. The concentrations of water leachable Ag, As, Cd, Cu, Cr, Ni, Pb, and Zn were below the US Environmental Protection Agency's ambient water quality criteria. Using the long-term 65-d life cycle Chironomus tentans test and 4 different endpoints (survival, adult emergence, egg case production, and number of eggs produced per female), no statistical differences were found between the DWTR treatments and the controls. Similarly, results obtained using the 10-d Hyalella azteca test showed no toxicity. However, although both survival and growth were recorded in all bioassays, the results of the 10-d C. tentans and the 28-d H. azteca tests were ambiguous. For C. tentans, 2 of the 3 DWTRs resulted in significantly lower survival rates compared to the controls. For H. azteca, no significant growth differences were observed between controls and DWTR treatments, but 2 of the 3 DWTRs resulted in significantly lower survival rates than the controls. Overall, these results suggest that certain DWTR substrates could be suitable for introduction to aquatic systems.

The diversity of aluminum-based drinking water treatment residuals for use in environmental remediation

“…This is unsurprising, given the desert environment of Utah, but it does highlight the caution needed prior to utilizing these materials for environmental remediation in freshwater environments. 7…”

“…These DWTRs were selected from a total of 15 samples after a screening step based on metal content guidelines for safe introduction of waste materials to aquatic environments. 7,17 Each DWTR sample is referred by the abbreviation of the state of originfor example, DWTR-TN refers to the sample from Tennessee. Dewatered DWTR samples provided by DWTPs were air-dried and subsequently ground.…”

“…This is unsurprising, given the desert environment of Utah, but it does highlight the caution needed prior to utilizing these materials for environmental remediation in freshwater environments. 7 Of the elements suitable for XAS analysis at the bending magnet beamline of the sector 5 of the Advanced Photon Source, only Mn and Fe are present in sufficient quantities to provide a sizable fluorescent signal. Like Ca, all samples show a discernible peak at the Fe K α line, with WY and OR showing particularly strong fluorescence.…”

“…3 Hazardous DWTRs, as often determined through toxicity characteristic leaching procedure (TCLP) results, may need to be disposed of at hazardous waste landfills or through the use of Class I well injections. 4 Even among non-hazardous DWTRs, there are historic and lingering concerns about their environmental impacts, including the potential release of aluminum in acidic environments, 5 issues due to compromised DWTP source waters, 6 potential adverse ecosystem impacts, 7,8 and the use of synthetic organic polymers to aid flocculation. 9 It is worth emphasizing that most studies have found limited to negligible environmental and health impacts from the disposal of these DWTRs, provided reasonable precautions are taken.…”