Colorado Water Oct 2005 - Laserfiche WebLink

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approximately half of those exceeded the proposed value of 5.9 ug /L, some by greater than ten times. The ef- fect from multiple endocrine disrup- tors, such as the suite of alkylphe- nolic compounds Liquid - liquid extractors studied here, is for identification of trace unknown but stud - organic chemicals ies have indicated an additive effect. Significant treat- ment occurs during infiltration and percolation through the soil absorption system of OWS, though the removal rates and mechanisms of OWCs prior to recharge to the environment are currently unknown. Additionally, there is the potential for treatment failure, by preferential flow through the soil, or from hydraulic failure, such as a storm event, that would send untreated wastewater with pollutant concentrations seen here directly to ground or surface water. Cur- rently, there are no established regulations for these compounds because little is still under- stood about the long -term reproductive effects of chronic exposure to pharmaceutically -active compounds at low concentrations such as those seen here. Of the nine surface waters sampled in the study, very few OWCs were identified, and, if present, were in low concentrations. Cholesterol and 4- methylphenol were the only compounds identi- fied in surface waters above the reporting level. The surface water sites are located in regions which rely heavily on OWS for wastewater treat- ment, but are not directly impacted by wastewa- ter from municipal wastewater treatment plant discharge. Instead, treated OWS effluent perco- lates through the soil until it reaches the water table and recharges the groundwater which may, in turn, recharge the local surface water. Surface water may also be impacted by runoff from agri- culture and development. In the ten ground- water wells, there were more OWCs identified at higher concentrations than in the surface waters. Every groundwater well was contaminated with at least one and at most seven of the 25 OWCs included in this study. Nine of the Surface water site sampled sites are drinking in the study water wells located up gradient on the same property as an OWS included in the study. In the OWS- reliant developments, contamination of these wells could indicate regional impacts to the groundwater from treated effluent recharge. Due to the widespread and growing use of OWS as an appropriate method of wastewater treat- ment, understanding the potential impacts on the receiving environments to which they dis- charge is critical. Results of this study indicate OWCs are present in OWS effluent frequently and in variable concentrations. Treatment oc- curs in the septic tank, in additional pre-treat- ment units such as filters and wetlands, and during percolation through the soil absorption field prior to groundwater recharge. Controlled laboratory- and field -scale transport studies are underway to investigate the key mechanisms of removal during soil treatment. OWCs have been identified in groundwater wells and, to a much lesser extent, in surface waters located in OWS- reliant regions. The results from the transport experiments in conjunction with the occurrence findings will aid in defining potential adverse effects to ecosystem and human health due to or- ganic wastewater contaminants discharge from onsite wastewater treatment systems. Additional funding for this project is provided by Colorado School of Mines.