Evaluating Site Specific Limitations for Removal of Organic Wastewater Contaminants in Onsite Wastewater System Soil Treatment Units

Tuesday, April 21, 2009: 4:50 p.m.
Joshua Tree (Hilton Tucson El Conquistador Golf & Tennis Resort )
Sarah M. Roberts , Hydrologic Science and Engineering, Colorado School of Mines, Golden, CO
John E. McCray , Hydrologic Science and Engineering, Colorado School of Mines, Golden, CO
Kathryn Lowe , Hydrologic Science and Engineering, Colorado School of Mines, Golden, CO
Organic wastewater contaminants (OWCs) are introduced into the environmental waters in significant concentrations in discharge from onsite wastewater treatment systems (OWS). OWCs include compounds in pharmaceutical drugs and household and personal care products. OWS are generally not designed with consideration for the treatment of these compounds, resulting in many of the more persistent compounds reaching groundwater and surface water where they may potential accumulate. This study recognizes five compounds as important for investigation of fate and transport characteristics in OWS soil treatment units based on various criteria. These criteria include toxicity to potentially affected organisms, persistence in the environment, and concentrations in wastewater discharge. The contaminants chosen are triclosan (antimicrobial), 4-nonylphenol and nonylphenol ethoxylates (surfactant degradants), 17β-estradiol (hormone), 1,4-dichlorobenzene (deodorant/insecticide), and diclofenac (non-steroidal anti-inflammatory drug). The purpose of this study is to evaluate and predict removal of these compounds in soil treatment units based on unit properties. Mechanisms for removal include abiotic degradation, irreversible sorption to soil, and aerobic and anaerobic biodegradation in soil. Removal rates for these mechanisms are estimated for each compound using literature reported data coupled with results from laboratory batch tests. Laboratory samples undergo a solid phase extraction method and are analyzed using select ion analysis in a gas chromatograph/mass spectrometer. Soil treatment unit properties include depth to groundwater or limiting condition, soil type, and dosing regime. Alternative or additional treatment methods are suggested for compounds that are not effectively treated in soil treatment units.