Fate of Estrogenic Compounds during Municipal Sludge Stabilization and Dewatering
Edward T. Furlong Dave Quanrud Beverley M. Stinson
OverviewThis project convened a team of experts in the fields of environmental engineering (AECOM), analytical chemistry and hydrogeology (USGS), and biological assay analysis (UA) to evaluate the occurrence and fate of estrogenic compound, and the estrogenicity of biosolids derived from wastewater treatment. Sludge and biosolids samples were collected through the solids treatment train of four wastewater treatment plants (WWTPs) operating a range of solids processing, treatment and disposal options that are typical to facilities across the United States. Targeted solids processing methods included thickening via gravity, gravity belt, and dissolved air flotation; stabilization via lime addition, aerobic digestion and anaerobic digestion; chemical conditioning; dewatering via centrifuge; and other processes including composting and pelletization. Targeted disposal options included beneficial reuse or disposal including land application, dedicated land disposal and landfilling. Samples were collected from the study plants between two and five times over two years, allowing for an assessment of seasonal variation. In some cases, sampling density was not sufficient to assess seasonal variations, but for certain compounds interesting seasonal trends were observed. The solids samples were supplemented by liquid samples at key locations in the study plants during several sample collection events.
Over the course of the study 15 sample trips were conducted and a total of 90 samples were collected from the four study plants. For each sample collected, chemical analysis for steroid hormones and in vitro biological assay (bioassay) measurements were conducted to quantify estrogen receptor agonists, antagonists, and estrogenic activity. In addition to the estrogenic compounds, samples were analyzed for a suite of trace organic compounds (TOrCs), including anthropogenic wastewater indicators (AWIs) and pharmaceuticals, resulting in analysis for over 100 chemical compounds in each liquid or solid sample. Collection of these data substantially expanded the scope and value of the study, providing a more comprehensive evaluation of the effects of solids processing and treatment on TOrCs. Loads of TOrCs and estrogenic activity were calculated for each sample point based on flows and solids loadings data from the study plants. In this exercise, TOrC concentrations are multiplied by the solids loading (tons per day) to calculate the daily load of each compound in grams per day (g/day). This report provides comparisons of the chemical and biological assays used in this study, the results of select TOrC mass balances as well as a discussion of the results and areas for future research.