Impacts of On-Site Wastewater Treatment Systems on Water Quality and Quantity in Urbanizing Watersheds

Non-Technical Summary: <BR>As widely as Onsite Wastewater Treatments Systems (OWTS) are used for wastewater treatment, their impact on water quality and quantity has not been elucidated to allow inclusion in land use planning projects. Currently, OWTS are blamed for poor water quality and considered consumptive water use. The overall project goal is determine the impact of OWTS on stream water quality and quantity in urbanizing watersheds of Ocmulgee and Oconee River basins in Georgia and promote behaviors and technologies that increase the effectiveness of OWTS. The selected watersheds are common in the Southern Piedmont region. The supporting objectives are to a) examine the difference in water quality and quantity of watersheds impacted by high versus low density OWTS, b) evaluate the utility, economics, and social acceptance of advanced treatment units (retrofitted to OWTS) to reduce pollutant load from OWTS, c) develop educational and extension materials on the impact of OWTS on water quality, emphasizing on the promotion and adoption of practices and technologies that result in improved water quality. Our study will achieve its objectives by studying 24 well characterized watersheds. Study results will enable stakeholders (policy makers, home owners, educators, regulatory officials, water managers) to make informed decisions on the installation, maintenance, and retrofitting of OWTS in new and existing developments. The study will provide information on the impact of OWTS on surface waters and social and economic factors affecting adoption of technologies for water quality improvement. OWTS- and watershed-scale models developed from the study will enable wider application of results. <P> Approach: <BR> The study area is found in the Southern Piedmont region, southeast of Atlanta, GA. The selected watersheds are in the Ocmulgee and Oconee River basins. Out of the 24 selected watersheds, twelve are characterized as having high density of OWTS with the remaining twelve characterized as having low density of OWTS. To quantify the impact of OWTS on water quantity, the groundwater contribution to streamflow (base-flow) will be quantified using synoptic measurements and by instrumenting four watersheds with streamgages, followed by analysis using hydrograph-separation techniques. Synoptic measurements will be taken concurrently with water sampling three times a year to capture the different (seasonal) flow conditions by using either volumetric or velocity-area methods. In addition to synoptic streamflow measurements, four sites will be equipped with continuous streamgages for storm flow measurements. Hydrograph separation between base and storm flows will be conducted using continuous streamflow data and the computer program HYSEP. Impact of OWTS on water quality will be evaluated by measuring bacterial indicators of fecal contamination, human specific viruses, hormones and nutrients using commercially available kits, Quantitative Polymerase Chain Reaction (qPCR), LC/MS/MS and other equipment following standard procedures of the Association of Official Analytical Chemists, American Public Health Association, American Water Works Association, and Water Environment Federation. Microbial and nutrient source tracking will be done using human specific markers and isotopic ratio analysis. Modeling will be performed at a scale of individual OWTS and the watershed scale. The OWTS-scale model will be used to predict groundwater recharge and N losses below the drainfield in different soils typical of the region using conventional OWTS and systems equipped with recirculating advanced treatment units. The watershed model will be used to predict the effect on base-flow, N, P, fecal bacteria, and hormone loads of adopting advanced treatment OWTS within the region. The drainfields of OWTS of volunteer home owners in high density OWTS watersheds will be monitored before and after retrofitting the OWTS with advanced treatment units to evaluate the improvement in water quality. An economic analysis of the effectiveness of retrofitting will be performed using willingness to pay surveys. A follow-up survey will be conducted in Year 2, after the education and outreach materials for this project have been developed and disseminated to evaluate their impacts. The results of this project will be delivered to the public and to professionals through a multifaceted educational program which will include targeted education of the general public at the watershed scale and incorporation into ongoing teaching, extension, and professional education programs at the state and national level. All data will be statistically analyzed for result compilation, interpretation and report and paper writing.