Global occurrence of Torque teno virus in water systems.

Bacterial indicator organisms are used globally to assess the microbiological safety of waters. However, waterborne viral outbreaks have occurred in drinking water systems despite negative bacterial results. Using viral markers may therefore provide more accurate health risk assessment data. In this study, fecal, wastewater, stormwater, surface water (fresh and salt), groundwater, and drinking water samples were analyzed for the presence or concentration of traditional indicators, innovative indicators and viral markers. Samples were obtained in the United States, Italy, and Australia and results compared to those reported for studies conducted in Asia and South America as well. Indicators included total coliforms, Escherichia coli, enterococci, male-specific coliphages, somatic coliphages and microviradae. Viral markers included adenovirus, polyomavirus, and a potential new surrogate, Torque teno virus (TTV). TTV was more frequently found in wastewaters (38-100%) and waters influenced by waste discharges (25%) than in surface waters used as drinking water sources (5%). TTV was also specific to human rather than animal feces. While TTV numbers were strongly correlated to other viral markers in wastewaters, suggesting its utility as a fecal contamination marker, data limitations and TTV presence in treated drinking waters demonstrates that additional research is needed on this potential viral indicator.

Using a weight-of-evidence approach for management of watersheds.

This research used a weight-of-evidence approach to evaluate sources of contaminants in a drinking water watershed that serves as part of the City of Boston's water supply. The approach incorporated land use analysis using GIS, sanitary surveys, traditional water quality monitoring and microbial source tracking (MST) tools. Case-study tributaries were selected based on elevated faecal coliform counts. Land use analysis and sanitary surveys were used to identify suspected microbial sources, including residential septic systems, agricultural animal operations, commercial/industrial operations and wildlife activity. Sampling sites were selected to hydrologically isolate potential contamination sources. Samples were collected seasonally over 1 year and analysed for traditional and MST parameters. Results demonstrated that both septic systems and a horse stable were contributing microbial loads in the first tributary. In the second tributary, septic systems from the townhouses were contributing microbial loads while a plant nursery was contributing organic matter. This evidence was used to evaluate best management practices to mitigate the contamination.

Effect of ozone on algae as precursors for trihalomethane and haloacetic acid production.

The effect of ozone on the trihalomethane (THM) and haloacetic acid (HAA) formation of two algae species was investigated. Scenedesmus quadricauda (green alga) and Cyclotella sp. (diatom) were cultured under controlled conditions and harvested in the log or late log growth phase. Experiments examined the formation of disinfection byproducts (DBPs) from the algal suspensions with and without preozonation. Preozonation with 1 mg/L increased chloroform formation from Scenedesmus by 17-44%. For Cyclotella, chloroform production increased by 5-26% with 1 mg/L ozone and by 39-109% with 3 mg/L ozone. Chlorinated HAA yields were not significantly increased after 1 mg/L ozone but increased by 38-76% for Cyclotella after 3 mg/L ozone. As compared to other sources of organic matter, algae under bloom conditions may contribute significantly to the DBP precursor pool. However, the majority of the DBP precursors (70%) were attributable to the cellular material, and thus removal of algae cells from a drinking water supply priorto oxidation will substantially reduce algal precursor concentrations.

State-of-the-art in two-dimensional ultrasonic transducer array technology.

Attention is given to means of sensing ultrasonic energy distributions over an area. Under the restraints appropiate to real-time imaging of deep body organs, piezoelectric arrays offer the most promising method. Adaptation of integrated circuit techniques to array assembly permits very large arrays of small elements to be batch fabricated. Further, special semiconductor switching devices specifically designed for addressing the array have been produced and applied. These permit both the passage of weak received signals and the application of voltage and current levels sufficient for transmission without significant disturbance of the basic piezoelectric element properties. Emphasis is placed on the complete data acquisition, processing, and display flexibility that arises from an array capability. Operation becomes possible in any of the presently used A or time motion (TM), in real time B or C scan, or in novel scan patterns adapted to specific organs. Further development with acoustic and electronic focusing, taking advantage of the unique possibilities obtained with the bidirectional array structure, is discussed.