Leonard W. Casson

Centralized Drinking Water Treatment Operations Shape Bacterial and Fungal Community Structure

Drinking water microbial communities impact opportunistic pathogen colonization and corrosion of water distribution systems, and centralized drinking water treatment represents a potential control for microbial community structure in finished drinking water. In this article, we examine bacterial and fungal abundance and diversity, as well as the microbial community taxonomic structure following each unit operation in a conventional surface water treatment plant. Treatment operations drove the microbial composition more strongly than sampling time. Both bacterial and fungal abundance and diversity decreased following sedimentation and filtration; however, only bacterial abundance and diversity was significantly impacted by free chlorine disinfection. Similarly, each treatment step was found to shift bacterial and fungal community beta-diversity, with the exception of disinfection on the fungal community structure. We observed the enrichment of bacterial and fungal taxa commonly found in drinking water distribution systems through the treatment process, for example, Sphingomonas following filtration and Leptospirillium and Penicillium following disinfection. Study results suggest that centralized drinking water treatment processes shape the final drinking water microbial community via selection of community members and that the bacterial community is primarily driven by disinfection while the eukaryotic community is primarily controlled by physical treatment processes.

Disinfection of Ebola Virus in Sterilized Municipal Wastewater.

Concerns have been raised regarding handling of Ebola virus contaminated wastewater, as well as the adequacy of proposed disinfection approaches. In the current study, we investigate the inactivation of Ebola virus in sterilized domestic wastewater utilizing sodium hypochlorite addition and pH adjustment. No viral inactivation was observed in the one-hour tests without sodium hypochlorite addition or pH adjustment. No virus was recovered after 20 seconds (i.e. 4.2 log10 unit inactivation to detection limit) following the addition of 5 and 10 mg L-1 sodium hypochlorite, which resulted in immediate free chlorine residuals of 0.52 and 1.11 mg L-1, respectively. The addition of 1 mg L-1 sodium hypochlorite resulted in an immediate free chlorine residual of 0.16 mg L-1, which inactivated 3.5 log10 units of Ebola virus in 20 seconds. Further inactivation was not evident due to the rapid consumption of the chlorine residual. Elevating the pH to 11.2 was found to significantly increase viral decay over ambient conditions. These results indicate the high susceptibility of the enveloped Ebola virus to disinfection in the presence of free chlorine in municipal wastewater; however, we caution that extension to more complex matrices (e.g. bodily fluids) will require additional verification.

On-Site Sodium Hypochlorite Generation

In this manuscript the on-site generation of sodium hypochorite for water and wastewater disinfection will be examined. The objective of this paper is to familiarize the reader with the equipment and operational requirements necessary for on-site sodium hypochlorite generation systems. This manuscript will review the following topics relative to on-site generation systems: • Understand the basic equipment requirements necessary for on-site generation of sodium hypochorite, • Understand the basic design considerations for in sodium hypochorite systems, and • Understand the operation and maintenance requirements of on-site generation systems.