Toxicity of Biosolid Elutriates from Different Wastewater Treatment Processes to Ceriodaphnia Dubia

Abstract

Biosolids from wastewater treatment plants (WWTPs) have a high content of nutrients and organic matter and are used as a land fertilizer constituent. However, biosolids can contain many toxic chemicals, including heavy metals and synthetic organic chemicals. Thus, land application of biosolids may introduce these toxicants to water resources through runoff or soil leachate. The objective of this study was to assess the toxicity of biosolid elutriates from different WWTP processes to Ceriodaphnia dubia. Class B biosolids and composted biosolids (Class A) were collected from six southeastern WWTPs. Elutriate from each biosolid sample was used as the test solution in 48 hour acute toxicity tests. Results indicated that elutriates were highly toxic (LC50 range 11.2%-35.5%) to C. dubia. A decrease in toxicity (completely alleviated) was observed for one elutriate from a composted biosolids sample, but an increase in toxicity was observed in the other. Reductions in dissolved oxygen concentrations in some tests confounded toxicity results. Elevated concentrations of 4-nonylphenol (4-NP) were found in several biosolid samples that had high elutriate toxicity. Additional chemical analyses are being conducted to identify other toxic compounds in elutriates and biosolids. Anticipated benefits include selection of different treatment and disposal methods of biosolids to reduce potential for toxicants to enter surface waters.