The objective of this study was to develop a method to monitor the microbial quality of treated drinking water at the tap utilizing point-of-use filter systems that are placed in water vending machines. Such vending machines have high-volume water throughput and allow for an evaluation of the occurrence of human enteric pathogens and fecal indicator bacteria in tap water over extended time periods. Seeded experiments, using Escherichia coli and bacteriophage MS-2, were performed on (i) new filters, (ii) artificially aged filters, and (iii) filters that had been used in the field (naturally aged filters) to evaluate the efficiency of recovery of these organisms from the three-component filter set (30 microm, 5 mirom, solid block carbon (SBC)) by evaluating each filter independently. SBC filters had the highest recovery of the organisms, averaging recovery of 27% and 5% for E. coli and MS-2, respectively. Subsequently, tapwatersupplieswere monitored in vending machinesthroughout Southern Arizona using SBC filters as a monitoring tool. A total of 48 filters from 41 unique site locations were surveyed for the presence of total coliforms, E. coli, enterococci, Cryptosporidium, enteroviruses, and noroviruses. Organisms were detected following the passage of large volumes of water ranging from 1000 to 17,000 L through the filters. Out of 48 SBC filters 54.2% were positive for at least one organism. The number of filters positive for total coliforms, E. coli, enterococci, and enterovirus was 13, 5, 19, and 3, respectively, corresponding to 27.1%, 10.4%, 39.6%, and 6.3% of the total filters. No filters were positive for noroviruses or Cryptosporidium. These results suggest that the SBC filter can be used to monitor large volumes of treated drinking water and detect the incidence of indicators and pathogens that may be present at low concentrations. These data show that post-treated water often contains water quality indicator and pathogenic organisms at the tap, and therefore, monitoring with this method would be beneficial to the community as it allows for an assessment of exposure to pathogens and associative risks. This monitoring tool will also aid in the tracking of outbreaks and the determination of the microbial pathogen load during all stages of an outbreak as a filter can be installed and retrieved at the point-of-use at anytime during an outbreak.

Advanced treatment of reclaimed water prior to potable reuse normally results in the inactivation of bacterial populations, however, incremental treatment failure can result in bacteria, including pathogens, remaining viable. Therefore, potential microorganisms need to be detected in real-time to preclude potential adverse human health effects. Real-time detection of microbes presents unique problems which are dependent on the water quality of the test water, including parameters such as particulate content and turbidity, and natural organic matter content. In addition, microbes are unusual in that: (i) viability and culturability are not always synonymous; (ii) viability in water can be reduced by osmotic stress; and (iii) bacteria can invoke repair mechanisms in response to UV disinfection resulting in regrowth of bacterial populations. All these issues related to bacteria affect the efficacy of real-time detection for bacteria. Here we evaluate three different sensors suitable for specific water qualities. The sensor A is an on-line, real-time sensor that allows for the continuous monitoring of particulates (including microbial contaminants) using multi-angle-light scattering (MALS) technology. The sensor B is a microbial detection system that uses optical technique, Mie light scattering, for particle sizing and fluorescence emission for viable bacteria detection. The last sensor C was based on adenosine triphosphate (ATP) production. E. coli was used a model organism and out of all tested sensors, we found the sensor C to be the most accurate. It has a great potential as a surrogate parameter for microbial loads in test waters and be useful for process control in treatment trains.

This study evaluated real-time sensing of Escherichia coli as a microbial contaminant in water distribution systems. Most sensors responded to increased E. coli concentrations, showing that select sensors can detect microbial water quality changes and be utilized as part of a contaminant warning system.Monitoring water distribution systems (DSs) for a microbial intrusion has been a challenge for water utilities. Many contaminants that can cause degradation in the water quality in DSs are not monitored, and contamination events are difficult to detect due to the low frequency of required samplings (6). As a consequence, DSs are relatively unprotected and vulnerable to intentional, natural, or accidental contamination from microbial agents (5). Therefore, there is a need for real-time monitoring to recognize water quality disturbances. To date there are a limited number of studies that have evaluated the use of commercial sensors for real-time monitoring of DSs, and even fewer that demonstrate how sensors respond to microbial contaminants. The objective of this study was to evaluate the potential of multiple water quality sensors for real-time monitoring of E. coli as a surrogate for microbial contamination.At the University of Arizona Real Time Monitoring Laboratory, water is delivered by the City of Tucson Water public utility. Deionized (DI) water as a control or prefiltered tap water (1-m pore size) was used during experiments, and a baseline output from the sensors was established. Sensors were arranged in parallel and challenged with two or more replicates of E. coli (ATCC 15597) at a final concentration of 10 3 , 10 4 , 10 5 , or 10 6 CFU/ml. The experiments used late-log-phase E. coli suspended in either tryptic soy broth (TSB) or phosphate-buffered saline (Sigma catalog no. P3813), termed "washed" (centrifuged three times at 4,000 rpm for 25 min). Water samples were obtained throughout the injection to confirm cultural analysis (by dilution, plating, and incubating at 37°C for 24 h on tryptic soy agar [BD catalog no. 236920]) or total cell analysis (by acridine orange direct count [AODC] [4]). A separate set of experiments neutralized the chlorine residual to allow for determination of the E. coli concentrations.Sensors evaluated included the Hach GuardianBlue event detection system, the BioSentry technology, the S::CAN Spectrolyser technology, and the GE 5310 online total organic carbon (TOC) unit. The BioSentry was the only sensor with the potential to detect microbial contaminants (categorizing particulates as rods, spores, protozoa, and unknown) and therefore was also evaluated to determine if it could differentiate turbidity-causing particulates from E. coli. E. coli at 10 4 and 10 5 CFU/ml with the addition of 0.3 nephelometric turbidity units (NTU) (Ricca Chemical catalog no. 8830-32) was evaluated for any increase in BioSentry response above the actual E. coli concentration due to the turbidity added to DI water. Most parameters analyzed in this study exhibited an increase in response to an inc...

This study developed a method for extracting infectious prions from Class B biosolids and subsequently evaluated the survival of infectious prions under the influence of mesophilic (37°C) and thermophilic (60°C) temperatures in Class B biosolids. Unlike other studies, this study utilized a scrapie cell assay to determine infectivity and quantity of infectious prions. The best method for extraction was exposing the biosolids to 4 M urea at 80°C for 10 minutes followed by a membrane centrifugation to reduce the concentration of urea. The recovery efficiency of the infectious prions from the biosolids for this method was 17.2%. In the survival study, a 2.43-log(10) reduction in prion infectivity was observed under mesophilic temperatures after 15 days and a 3.41-log(10) reduction after 10 days under thermophilic conditions. The reduction of infectious prions was greater in the biosolids than the control in phosphate buffered saline, suggesting factors other than temperature were also playing a role in the loss of infectivity of the prions in the biosolids.