Author: Jennifer Ann DoughertyPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The contamination of water supplies by organic contaminants such as pharmaceuticals and personal care products (PPCPs) pose a potential risk to the health of humans and ecosystems. Septic systems under the best circumstances produce effluent quality equivalent to biologically or secondarily treated wastewater, which is known to be inefficient for removal of many PPCPs. This dissertation examines septic systems as a source of PPCP pollution. The occurrence, fate, and transport of a set of 25 organic contaminants commonly found in wastewater was studied at the scale of a watershed, a septic system, and in microcosms that simulated the geochemical conditions of a septic plume. The septic system study was carried out at Stinson Beach, CA and the watershed study at Liberty Bay, WA. The tested compounds included 19 pharmaceuticals, three personal care products, two herbicides and one flame retardant. They encompassed a structurally diverse group of chemicals with a wide range of physicochemical properties, with Log Kow ranging -0.07 to 4.77 as well as acidic and basic properties. First, sediments from Stinson Beach, CA were used in batch microcosm experiments to assess biotransformation and sorption under conditions simulating an aerobic groundwater system and the nitrate and sulfate reducing conditions of a septic plume. Transformation was found, in general, to be slower under anaerobic conditions than aerobic conditions. Half-lives ranged from 4 days to longer than 365 days for all conditions. Sorption did not fit the commonly used hydrophobic models governed by Log Kow, indicating the significance of factors other than hydrophobicity. These factors may include hydrogen bonding and electrostatic attraction due to one or several polar functional groups. Second, the occurrence and transport of PPCPs in a single septic system along the California coast was documented. Findings indicated that many PPCPs were refractory and mobile under the conditions of a leach field contaminant plume. Finally, in a watershed scale study in Liberty Bay, Washington, the occurrence of PPCPs thought to originate from septic systems was evaluated. The findings are consistent with laboratory data and usage patterns. The overall results of this dissertation suggest that septic systems, which support 25% of the United States population, may be a significant source of PPCP contamination to groundwater and surface waters.
