Tributary Pollutant Source Study. Consoer-Townsend-Envirodyne Engineers (W.P. Hamilton, PI).
Fecal pollution in urban streams results in a major financial burden to state and local governments charged with complying with and enforcing the Clean Water Act. In an urban watershed, the potential sources of fecal bacteria are numerous, due to the coexistence of humans with wildlife, livestock, and domestic animals. In order to attack a fecal bacteria problem effectively, best management practices must target the primary polluters. Current approaches to monitoring for fecal contamination in recreational waters involve the use of indicator organisms to signal the presence of pathogenic bacteria. While this monitoring approach is cost-effective (compared with monitoring for the suite of possible viral and bacteriological agents that could pose a human health risk) it is not source-specific, and thus the presence of these microbes alone does not direct remedial efforts. Current methods for discriminating between bacterial pollutant sources are either expensive (i.e., molecular techniques such as PCR) or problematic (FC/FS ratios, alternative indicator organisms, fecal sterols, etc). It has long been known that microorganisms exposed continuously to antibiotic agents can develop resistance; it is also true that different antibiotics are used to treat different animal populations. By exposing microorganisms from known sources (wildlife, domesticated pets, livestock, human) to a suite of antibiotics, patterns in resistance can be observed, and, given enough samples, a database of antibiotic resistance profiles can be prepared for all potential polluters. By comparing the resistance pattern of a sample of unknown origin to the database of known source resistance profiles, the source of the unknown can be determined. In addition, the cost of this analysis is low, and requires no more sophisticated equipment or materials and no more advanced training than current culturing techniques.

Removal of Mercury from Savannah River Site Wastewater Using Metal Sulfides, CRESP (Leader: W.P. Hamilton).
Mercury (Hg) is classified by the United States Environmental Protection Agency (US EPA) as a persistent, bioaccumulative, and toxic compound (40 CFR Part 372), and therefore its release into natural systems is closely scrutinized by state and federal regulators (US EPA, 1997b). In natural sediments, microorganisms can bioconvert inorganic Hg to the neurotoxin methylmercury, which is bioaccumulated in fish and piscivorous species (Jensen And Jernelöv, 1969; King et al., 2000). Thus, strict discharge limits have been placed on Hg, typically well below drinking water limits (i.e., nanograms per liter). Because of these strict limitations, methods are needed that reduce the concentration of Hg in industrial discharges and which do so at an affordable cost. Many commercially available treatment techniques can reduce Hg to the ultra low levels for dollars per 1000 gallons of water treated (US EPA, 1997a). However, methods that can provide treatment for pennies per 1000 gallons are needed. We propose a method for removing aqueous Hg by exploiting the complex aqueous chemistry of Hg. Under reducing conditions in the presence of reduced sulfur, Hg can form one of two polymorphs of mercuric sulfide (HgS), cinnabar and metacinnabar. Both compounds are extremely insoluble, with solubility product constants (Ksp) on the order of 10-52 (Smith and Martell, 1976). Thus, relatively the presence of soluble metal sulfides such as FeS or MnS may provide enough dissolved sulfide to precipitate dissolved Hg and thus may offer an inexpensive yet efficient means for removing Hg from aqueous systems.