Grantee Research Project Results
The Fate and Transport of Emerging Chemical Contaminants through Septic SystemsEPA Grant Number: F5D30802
Title: The Fate and Transport of Emerging Chemical Contaminants through Septic Systems
Investigators: Chalew, Talia
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Hahn, Intaek
Project Period: August 25, 2005 through August 31, 2006
Project Amount: $74,000
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
Unlike wastewater treatment plants whose operations are regulated, septic system effluent quality is not monitored and the homeowner bares sole responsibility for maintaining a functioning septic system. Septic systems have been studied for their effectiveness at removing nutrients and pathogens, but not emerging contaminants, such as the endocrine active substances (EASs) proposed for investigation in this project. Without proper maintenance, septic systems fail. It is estimated that nearly half the septic systems in North Carolina are no longer effective, which is a scenario likely to be found across the U.S. With such failure, the soil can no longer detoxify the effluent effectively and chemical constituents would have higher potential to reach surface and ground waters. This project will include careful selection of representative chemicals, such as EASs, that are expected to survive septic system treatment. Chosen compounds will be surrogates for a wide range of household chemicals. These compounds will be assessed through the septic system with calculations of concentration in waste influent, detection in septage, and occurrence detection in the aquatic environment. These compounds can be used to source track contamination from septic systems to surface and ground waters. This is an important tool for protecting the environment and human health by preserving natural resources that serve as drinking water sources.
The objective of this project is to study the fate of emerging chemical contaminants, including EASs, through septic systems in North Carolina. This project will identify indicators that can determine whether chemical contaminants from failed septic systems reach nearby surface waters.
For this study, emerging chemical contaminants representative of household use will be selected that are known to survive conventional wastewater treatment and are expected to be present in septic system effluent. If this hypothesis is verified, the presence of such chemicals in surface waters would be indicative of non-point sources of contamination. Over the past year, I have conducted a thorough literature review assessing chemical properties, usage, and environmental fate of several such compounds. Preliminary calculations were conducted to estimate their levels in septic tank influent and effluent based on the levels of active constituents in the consumer product, typical product usage patterns, and average water usage. I have learned and will continue to perfect solid-phase extraction, liquid chromatography- mass spectrometry, and gas chromatography- mass spectrometry methods to detect these compounds in aqueous and solid samples. Methods will be adapted for the analysis of the selected chemicals in septage.
Beginning this summer (2005), field samples will be collected to detect the occurrence of the candidate chemicals. Failing septic systems in close proximity to surface water will be identified with the help of the North Carolina Department of Environment and Natural Resources. Accurate data will be collected from households regarding water and relevant product usage to adjust predictive model. Samples of septage and effluent will be analyzed for the selected compounds. The presence of these compounds will imply the likelihood for movement in the environment. Samples will then be collected from various points in surface waters impacted by runoff from failed septic systems as well as from groundwater wells to assess the fate of these "indicator" compounds and viability of their selection as surrogate measures of non-point source contamination. If compounds are detected, I will attempt to quantify the risk to human health at these exposure levels.
I expect that emerging chemicals, such as EASs, are not degraded by the anaerobic septic tank and will be present in septic septage and effluent. As a consequence, these and other chemicals are likely to be found in surrounding aquatic environments.
This research will broaden the understanding of septic system contribution of EASs to the environment and will illustrate whether current on-site waste treatment is adequate to prevent discharge of emerging chemical contaminants. This project will generate a quantitative monitoring tool that can be used to control impairment of streams and risk assessment of non-point pollution contribution to the environment.