Turbidity is a widely used parameter around the world for describing drinking water quality. Sometimes, turbidity at water treatment plant outlets may reach high values during short periods of time, and this is acceptable according to some current drinking water regulations. In this study, the quantity and nature (chemical and microbiological) of suspended matter, which may travel throughout a distribution system (DS) during turbid events — affecting both raw water and water treatment — were evaluated. Treated water included filtration with no coagulant addition. During turbid events, the concentration of suspended particles increased in treated water, and a similar increase (quantity and nature) was observed throughout the DS. Bacterial indicators of contamination (total and fecal coliforms, enteroccocci, spores of Clostridium perfringens) were not found in either treated water nor in the DS during turbid events. Nevertheless, a higher bacterial aerobic spore concentration was associated with turbid events for raw, treated, and distributed water, therefore suggesting the potential passage of pathogens, if present in raw waters. Cultivable bacteria concentrations remained low in treated and distributed water regardless of the turbidity. These results emphasize the need to carefully monitor raw and treated water quality for utilities using "high quality" water resources with limited treatment barriers, especially when such water resources are affected by even slight turbidity variations. Key words: aerobic spore-forming bacteria, distribution system, drinking water, filtration, turbidity, suspended particles, water quality.

ABSTRACT The viral infectivity factor (Vif) of human immunodeficiency virus type 1 (HIV-1) neutralizes an unidentified antiviral pathway that occurs only in nonpermissive (NP) cells. Using a yeast two-hybrid screen of a human lymphocyte cDNA library, we identified several potential Vif partners. One, the nuclear body protein Sp140, was found specifically in all NP cells (n = 12 cell lines tested; P ≤ 0.001), and HIV-1 infection induced its partial dispersal from nuclear bodies into cytosolic colocalization with Vif. Our results implicate Sp140 in a response to HIV-1 that may be related to or coordinated with the pathway that inactivates HIV-1 lacking vif.

nderstanding distribution system water quality is a complex task because it involves not only numerous parameters but also the interactions among these parameters. This article highlights the development of a visualization tool capable of showing all types of information—modeled and measured parameters— simultaneously or independently as a function of space or time. In this study, diversified databases that included such system parameters as structure, hydraulics, and water quality were compiled and explored spatially and temporally through the visualization software. This approach proved to be successful in identifying probable sources of water contamination at a specific sampling point. It also helped establish general relationships between distribution system parameters, i.e., pipe breaks, pipe age, and water pressure, that are often difficult to link. A clearer understanding of the reasons for water quality degradation during distribution is important to water suppliers because research has suggested that such degradation increases the rate of gastrointestinal illnesses. When water quality is questionable, often the only parameters taken into account are measurements of water characteristics. Visualization of multiple parameters at one time enables utilities to pinpoint the source of their water quality problems and distinguish which areas of the distribution system are most at risk.—MPM U

The very marked decay of chlorine measured in one section of the distribution system of a large North American city, and the fluctuations in this decay, were studied. The results obtained from operational data collection, from dedicated flow measurements and from Epanet hydraulic modelling demonstrate that low chlorine residuals in this particular distribution system section cannot be attributed to any exceptional consumption by corrosion particles, loose deposits or biofilms. On the contrary, the hydraulic configuration of this distribution system area (tank design and pumping cycles) results in such high residence times that the low chlorine residuals observed are self-explanatory. Detailed analysis of the EPANET results indicates that the principles of the hydraulic (dys)functioning in this zone are well described by the model, which can be relied upon to compute and compare several design or operational solutions to minimize residence times, thereby increasing the chlorine residual in the area.