Robert S. Reimers

Lymphocyte proliferative response and tissue distribution of methylmercury sulfide and chloride in exposed rats

The immunotoxic effects and tissue distribution of different forms of methylmercury compounds were studied in rats. Methylmercury sulfide or methylmercury chloride was fed to rats at concentrations of 5 or 500 microg/L in drinking water for 8 wk. T-cell lymphocyte proliferative response to phytohemagglutinin (PHA) and determination of tissue distribution of mercury by gas chromatography using electron capture were assayed. Four different forms of mercury compounds were employed: MeHgS-, (MeHg)2S, (MeHg)3S+, and MeHgCl. Results indicated that exposure to methylmercury significantly enhanced lymphocyte responsiveness in most of the exposed groups at the low concentration of 5 microg/L, with the highest proliferative response (fourfold increase) in the MeHgCl group. At 500 microg/L, a significant decrease in the lymphocyte proliferative response was observed in the (MeHg)3S+ and MeHgCl groups; conversely, the MeHgS(-)- and (MeHg)2S-exposed animals had a modest increase of the lymphocyte proliferative response. The largest concentrations of all four mercury forms were detected in the kidney and spleen. The levels of mercury found in kidney, spleen, liver, brain, and testis were lower in the MeHgCl group than in those exposed to (MeHg)2S and (MeHg)3S+. These data indicate that the organ distribution of mercury and immune alteration may vary according to the chemical structure of the compound. This observation may have important implications in humans potentially exposed to low levels of methylmercury present in the environment, since the immune system plays an important regulatory role in the host-defense mechanisms.

Electron beam inactivation of selected microbial pathogens and indicator organisms in aerobically and anaerobically digested sewage sludge.

Microbial pathogens in municipal sewage sludges need to be inactivated prior to environmental disposal. The efficacy of high energy (10 MeV) e-beam irradiation to inactivate a variety of selected microbial pathogens and indicator organisms in aerobically and anaerobically digested sewage sludge was evaluated. Both bacterial and viral pathogens and indicator organisms are susceptible to e-beam irradiation. However, as expected there was a significant difference in their respective e-beam irradiation sensitivity. Somatic coliphages, bacterial endospores and enteric viruses were more resistant compared to bacterial pathogens. The current US EPA mandated 10 kGy minimum dose was capable of achieving significant reduction of both bacterial and viral pathogens. Somatic coliphages can be used as a microbial indicator for monitoring e-beam processes in terms of pathogen inactivation in sewage sludges.

Disinfecting and Stabilizing Biosolids Using E-Beam and Chemical Oxidants

Municipal sewage and sludges can harbor a variety of infectious microorganisms as well as estrogenic compounds and their metabolites. Biosolids and other residuals generated from municipal wastewater treatment facilities need to be used for beneficial purposes such as land application. To reduce the potential for adverse environmental and human impacts, it is critical that novel approaches be investigated so that municipal biosolids can be disinfected and stabilized to reduce the pathogen loads and levels of estrogenic compounds. The overall objective of this project was to demonstrate the disinfection and enhanced stabilization of municipal biosolids when high energy (10 MeV) Electron Beam (e-beam) technology is coupled with oxidants such as chlorine dioxide and ferrate. High energy E-Beam is effective as a disinfection technology. Significant reductions of all target organisms can be achieved in municipal biosolids depends on the dose that is employed. An e-beam treatment system utilizing 15 kGy e-beam dose has been designed and mathematically modeled and validated. Based on these engineering design considerations, e-beam treatment was shown to be cost-effective. There was synergistic disinfection of pathogens when e-beam is coupled with oxidants such as chlorine dioxide and ferrate. E-Beam at 8 kGy was unable to destroy estrogenic activity in the sludge samples. Ferrate (100 ppm) was capable of destroying estrogenic activity in the biosolid samples with or without the addition of e-beam irradiation. Chlorine dioxide (100 ppm) was not effective at destroying the estrogenic activity either by itself or in combination with e-beam. The combination of 100 ppm of ferrate with 8 kGy of e-beam promoted the stabilization of aerobic and anaerobic sludge samples as indicated by BOD, VSS and SOUR test results. The results demonstrate that 10 MeV e-beam is capable of cost-effectively inactivating a variety of bacterial and viral pathogens in aerobically and anaerobically digested biosolids. Overall, thes results suggest that when e-beam is combined with ferrate significant reductions of microbial pathogens, estrogenic compounds and biosolid stabilization can be achieved. This title belongs to WERF Research Report Series . ISBN: 9781843392996 (eBook)

Using Lime to Beneficially Manage Wastewater Treatment Plant Residuals: A Review and Assessment of the Practice for Producing an Exceptional Quality Product

Lime is used to prepare residuals for safe beneficial use by preventing the biodegradation of organic material and either reducing the numbers (of) or eliminating any pathogenic organisms present. Lime acts in several ways including: elevating the pH and holding it at a high level for a period of time; and in some instances elevating the temperature of the residuals to a high level and maintaining it there for a specified period of time. The performance of any lime treatment system is, however, only as good as the quality of alkaline material selected, the dosage level applied, the mixing method selected and applied, the time allowed for all reactions to reach completion, and the monitoring methods employed for pH and temperature.