Near Real-Time Detection of E. coli in Reclaimed Water.

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.

Evaluation of select sensors for real-time monitoring of Escherichia coli in water distribution systems.

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.

Survival of infectious prions in Class B biosolids.

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.

Survival of infectious prions in water.

The objective of this study was to evaluate the fate of infectious prions in water. Known concentrations of infectious prions were added to deionized water, tap water, and wastewater. Samples were incubated at 25°C, 37°C, and 50°C for 1 to 8 weeks. The standard scrapie cell assay (SSCA) which includes the ELISPOT (Enzyme Linked Immuno-Spot) reaction was performed to determine prion infectivity and quantity as a function of time. A reduction of infectious prions was observed at 25°C, 37°C, and 50°C ranging between 0.5-log10 and 1.4-log10 in one week. Results suggest that organic matter was instrumental in protecting infectious prions, allowing them to remain infectious for a longer period of time. Thus, our data effectively show a quantifiable reduction of infectious prions in water and identifies some of the components that may influence infectivity.

Point-of-Use drinking water devices for assessing microbial contamination in finished water and distribution systems.

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.