In 2010 the Pittsburgh (Pa.) Water and Sewer Authority (PWSA) observed a significant increase in the concentration of total trihalomethanes (TTHMs), especially brominated THM species, in its finished water. In an effort to explain these changes, PWSA and the University of Pittsburgh's Swanson School of Engineering investigated bromide concentrations in the Allegheny River (PWSA's source water) and THM formation in PWSA's drinking water. Results of the investigation indicated that elevated bromide concentrations in the source water were associated with increased concentrations of TTHMs, especially brominated THMs, in the drinking water. Additionally, a survey of the river system suggested that industrial wastewater treatment plants (brine plants) treating Marcellus Shale wastewater, as well as other wastewaters, were major contributors of bromide in the raw water. The study results also indicated that PWSA's conventional treatment process, which includes enhanced coagulation and secondary sedimentation, was ineffective at removing bromide from the source water. The increase in bromide concentrations in the Allegheny River system could affect the ability of conventional drinking water plants drawing water from this source to comply with the Stage 2 Disinfectants/Disinfection Byproducts Rule.

A study was conducted to compare the susceptibility of legionellae and coliforms to disinfection by chlorine. The chlorine residuals used were similar to concentrations that might be found in the distribution systems of large public potable water supplies. The effects of various chlorine concentrations, temperatures, and pH levels were considered. A number of different Legionella strains, both environmental and clinical, were tested. The results indicate that legionellae are much more resistant to chlorine than are coliform bacteria. At 21°C, pH 7.6, and 0.1 mg of free chlorine residual per liter, a 99% kill of L. pneumophila was achieved within 40 min, compared with less than 1 min for Escherichia coli. The observed resistance is enhanced as conditions for disinfection become less optimal. The required contact time for the removal of L. pneumophilia was twice as long at 4°C than it was at 21°C. These data suggest that legionellae can survive low levels of chlorine for relatively long periods of time.

HartmanneUla vermiformis, a common amoebal inhabitant of potable-water systems, supports intracellular multiplication of Legionela pneumophila and is probably important in the transportation and amplification of legionellae within these systems. To provide a practical guide for decontamination of potable-water systems, we assessed the chlorine and heat resistance ofH. verrniformis. H. vermiformnis cysts and trophozoites were treated independently with chlorine at concentrations of 2.0 to 10.0 ppm for 30 min and then cocultured with L. pneumophila. Both cysts and trophozoites were sensitive to concentrations between 2.0 and 4.0 ppm and above (trophozoites somewhat more so than cysts), and 10.0 ppm was lethal to both forms. Hartmannellae treated with chlorine up to a concentration of 4.0 ppm supported the growth of legionellae. To determine whether heat would be an effective addendum to chlorine treatment of amoebae, hartmannellae were subjected to temperatures of 55 and 60°C for 30 min and alternatively to 50°C followed by treatment with chlorine at a concentration of 2 ppm. Fewer than 0.05% of the amoebae survived treatment at 55°C, and there were no survivors at 60°C. Pretreatment at 50°C appeared to make hartmannella cysts more susceptible to chlorine but did not further reduce the concentration of trophozoites.

Previous studies have shown that bacteria maintained in a low-nutrient "natural" environment such as swimming pool water are much more resistant to disinfection by various chemical agents than strains maintained on rich media. In the present study a comparison was made of the chlorine (Cl2) susceptibility of hot-water tank isolates of Legionella pneumophila maintained in tap water and strains passaged on either nonselective buffered charcoal-yeast extract or selective differential glycine-vancomycin-polymyxin agar medium. Our earlier work has shown that environmental and clinical isolates of L. pneumophila maintained on agar medium are much more resistant to Cl2 than coliforms are. Under the present experimental conditions (21°C, pH 7.6 to 8.0, and 0.25 mg of free residual Cl2 per liter, we found the tap water-maintained L. pneumophila strains to be even more resistant than the agar-passaged isolates. Under these conditions, 99% kill of tap water-maintained strains of L. pneumophila was usually achieved within 60 to 90 min compared with 10 min for agar-passaged strains. Samples from plumbing fixtures in a hospital yielded legionellae which were "super"-chorine resistant when assayed under natural conditions. After one agar passage their resistance dropped to levels of comparable strains which had not been previously exposed to additional chlorination. These studies more closely approximate natural conditions than our previous work and show that tap water-maintained L. pneumophila is even more resistant to Cl2 than its already resistant agar medium-passaged counterpart.

Studies were conducted to investigate the survival and multiplication of Legionella spp. in public drinking water supplies. An attempt was made, over a period of several years, to isolate legionellae from a municipal system. Sampling sites included the river water supply, treatment plant, finished water reservoir system, mains, and distribution taps. Despite the use of several isolation techniques, Legionella spp. could not be detected in any of the samples other than those collected from the river. It was hypothesized that this was due to the maintenance of a chlorine residual throughout this system. To investigate the potential for Legionella growth, additional water samples, collected from throughout the system, were dechlorinated, pasteurized, and inoculated with Legionella pneumophila. Subsequent growth indicated that many of these samples, especially those collected from areas affected by an accumulation of algal materials, exhibited a much greater ability to support LegioneUa multiplication than did river water prior to treatment. Chemical analyses were also performed on these samples. Correlation of chemical data and experimental growth results indicated that the chemical environment significantly affects the ability of the water to support multiplication, with turbidity, organic carbon, and certain metals being of particular importance. These studies indicate that the potential exists for Legionella growth within municipal systems and support the hypothesis that public water supplies may contaminate the plumbing systems of hospitals and other large buildings. The results also suggest that useful methods to control this contamination include adequate treatment plant filtration, maintenance of a chlorine residual throughout the treatment and distribution network, and effective covering of open reservoirs.

A model was developed to study the multiplication of various Legionella spp. in tap water containing Hartmannella vermiformis. Tap water cultures prepared with the following components were suitable for the multiplication studies: Legionella spp., 103 CFU/ml; H. vermiformis, 104.4 cysts per ml; and killed Pseudomonas paucimobilis, 109 cells per ml. Cocultures were incubated at 37°C for at least 1 week. The following legionellae multiplied in tap water cocultures in each replicate experiment: L. bozemanii (WIGA strain), L. dumoffii (NY-23 and TX-KL strains), L. micdadei (two environmental strains), and L. pneumophila (six environmental strains and one clinical isolate). Growth yield values for these strains were 0.6 to 3.5 log CFU/ml. Legionellae which did not multiply in replicate cocultures included L. anisa (one strain), L. bozemanii (MI-15 strain), L. micdadei (a clinical isolate), L. Iongbeachae, (one strain), and L. pneumophila (Philadelphia 1 strain). L. gormanii and an environmental isolate of L. pneumophila multiplied in only one of three experiments. None of the legionellae multiplied in tap water containing only killed P. paucimobilis. The mean growth yield (± standard deviation) of H. vermiformis in the cocultures was 1.2 + 0.1 log units/ml. H. vermiformis supports multiplication of only particular strains of legionellae, some of which are from diverse origins.

Since the events of Sept. 11, 2001, the world has become a different place. More attention than ever is being paid to the nation's vulnerabilities, and this has prompted officials at all levels to examine the tools available for ensuring the security of public utilities. The recent emphasis on making sure that public water supplies are safe has created the need for continuous monitoring systems and analytical techniques that can be used at the utility level to test for a variety of toxic materials in a short amount of time. States and colleagues provide a survey of continuous monitoring and analytical methods currently available to utilities for security purposes. This survey grew out of an investigation the Pittsburgh (Pa.) Water & Sewer Authority (PWSA) and the University of Pittsburgh School of Engineering conducted in order to identify feasible analytical responses to security concerns. This investigation included a literature search; discussions with personnel from various water utilities, water industry organizations, and regulatory agencies; and evaluation of several commercially available monitoring and analytical systems. The article also takes a look at the analytical measures PWSA uses to screen for possible contamination in response to threats or suspected tampering with its water system as well as during times of heightened security. Although these methods are limited and their results should be interpreted with caution, there are some techniques, such as acute toxicity testing, that can be useful.

Nursing homes as well as hospitals are at risk for Legionella contamination. Hospital‐acquired Legionnaires' disease, associated with contaminated hot water plumbing systems, is a well‐documented problem in hospitals and may also be a problem in nursing homes. In this study, four nursing homes were surveyed to determine the extent to which potable hot water systems were colonized by Legionella pneumophila and to measure microbial and chemical factors related to legionellae contamination. The survey indicated that two of the homes were heavily contaminated with Legionella and suggested that contamination is associated with hot water temperatures, chlorine concentrations, the presence of free‐living amoebae, and possibly intermittent seeding of building plumbing systems with legionellae from the public water supply. The most heavily colonized nursing home plumbing system was then equipped with a copper‐silver ionization device, designed to control Legionella. A subsequent two‐year evaluation indicated that the device controlled Legionella but not amoebae or non‐Legionellaceae bacteria. Maintenance of the ionization system and monitoring of legionellae and metals concentrations in the water are important for effective use of the control device.