Assessing residential activity in a home plumbing system simulator: monitoring the occurrence and relationship of major opportunistic pathogens and phagocytic amoebas.

Opportunistic premise plumbing pathogens (OPPPs) have been detected in buildings' plumbing systems causing waterborne disease outbreaks in the United States. In this study, we monitored the occurrence of OPPPs along with free-living amoeba (FLA) and investigated the effects of residential activities in a simulated home plumbing system (HPS). Water samples were collected from various locations in the HPS and analyzed for three major OPPPs: Legionella pneumophila, nontuberculous mycobacterial species (e.g., Mycobacterium avium, M. intracellulare, and M. abscessus), and Pseudomonas aeruginosa along with two groups of amoebas (Acanthamoeba and Vermamoeba vermiformis). A metagenomic approach was also used to further characterize the microbial communities. Results show that the microbial community is highly diverse with evidence of spatial and temporal structuring influenced by environmental conditions. L. pneumophila was the most prevalent pathogen (86% of samples), followed by M. intracellulare (66%) and P. aeruginosa (21%). Interestingly, M. avium and M. abscessus were not detected in any samples. The data revealed a relatively low prevalence of Acanthamoeba spp. (4%), while V. vermiformis was widely detected (81%) across all the sampling locations within the HPS. Locations with a high concentration of L. pneumophila and M. intracellulare coincided with the highest detection of V. vermiformis, suggesting the potential growth of both populations within FLA and additional protection in drinking water. After a period of stagnation lasting at least 2-weeks, the concentrations of OPPPs and amoeba immediately increased and then decreased gradually back to the baseline. Furthermore, monitoring the microbial population after drainage of the hot water tank and partial drainage of the entire HPS demonstrated no significant mitigation of the selected OPPPs. This study demonstrates that these organisms can adjust to their environment during such events and may survive in biofilms and/or grow within FLA, protecting them from stressors in the supplied water.

Fate of ammonia and implications for distribution system water quality at four ion exchange softening plants with elevated source water ammonia.

Hard water and elevated ammonia are problems for many United States groundwater drinking water utilities, and some utilities, particularly those in the Midwest, face both challenges. Ion (cation) exchange (IX) is a common treatment technique for hardness reduction (i.e., softening) and may be used to remove ammonia as well, but these constituents may compete in IX and impact overall treatment performance. Few data have been reported on the impact on ammonia concentrations when using IX for softening in full-scale systems. This study investigated four full-scale groundwater treatment plants in Illinois that practice IX for softening (raw water hardness > 220 mg/L as CaCO3) and have elevated groundwater ammonia concentrations (> 2 mg N/L). Sampling throughout the year revealed consistent finished water hardness levels but variable ammonia concentrations. Ammonia removal varied and depended on how much water had been treated since the last regeneration. High ammonia removal (sometimes > 90%) occurred in the first half of the IX service cycle, while effluent ammonia concentrations increased compared to the influent (sometimes > 200%) towards the end of the IX cycle (total length 50,000-92,000 gallons [190-350 m3]). Ammonia removal efficiency varied among the plants, but the overall trends were similar. Because variable ammonia concentrations may make it difficult to produce a consistent total chlorine residual, they can negatively impact disinfection and water quality in the distribution system. Ammonia concentrations should be considered when designing softening systems to determine regeneration frequency, develop blending strategies, or include an alternative ammonia treatment process before IX softening to produce a more stable and consistent finished water.

Effectiveness of point-of-use and pitcher filters at removing lead phosphate nanoparticles from drinking water.

Orthophosphate (PO4) addition is a common corrosion control treatment used to lower lead (Pb) concentrations at the consumer's tap by forming relatively insoluble Pb-phosphate (Pb-PO4) minerals. However, some Pb-PO4 particles that can form in drinking water are mobile nanoparticles (i.e., 0.001-0.1 µm) that have the potential to reach the tap. Point-of-use (POU) or pitcher filters are often used to manage risks during distribution system upsets, when corrosion control treatment is not optimized, or following Pb service line replacements. To abide by industry convention, POU and pitcher filters must be NSF/ANSI-certified for Pb reduction (NSF/ANSI-53) using a test water containing dissolved Pb and large Pb particles. Certification for particulates reduction (NSF/ANSI-42) is done using a test water that contains particles, but not leaded particles. To address the lack of testing for Pb nanoparticles, this study challenged six certified commercially available faucet-mounted POU (3) and pitcher (3) filters with aqueous suspensions of Pb-PO4 nanoparticle. For the water quality investigated, the Pb particles formed ranged between 0.016 and 0.098 µm, based on scanning electron microscopy, transmission electron microscopy, and dynamic light scattering analysis. These particles represented 98.5% of total Pb in suspension. The total Pb removals were between 44.6 and 65.1% for the POU filters, and between 10.9 and 92.9% for the pitcher filters. The electron microscopy results confirm that Pb-PO4 nanoparticles passed through the filters. The findings can inform future efforts to re-examine the test waters used in the certification challenge tests.

The impact of sampling approach and daily water usage on lead levels measured at the tap.

There are many sampling approaches available for lead (Pb) in drinking water. Selecting the best approach for its intended use is critical. The objective of this work was to compare water Pb levels collected by multiple sampling approaches from a model home plumbing system (HPS) that included an old Pb service line (LSL), as a function of daily water usage. Specifically, flushed, direct LSL, sequential profile, random daytime (RDT), first draw, and manual composite samples were compared, and daily water usage rates ranged from 1.4 to 120 gallons/day (5.3-454.2 L/day). Pb levels in water collected directly from the LSL reached equilibrium after 7-15.5 h of stagnation, and approximately 55% of the equilibrium Pb concentration was reached after 2 h. Sequential sampling accurately identified the LSL; however, the peak profile Pb concentrations were a fraction of the Pb measured directly from the LSL. Daily water usage patterns greatly impacted total Pb levels in all water sampling approaches, although manual composite and RDT samples were more sensitive to changes. Manual composite and RDT samples were equal to or greater than first draw samples throughout the study, and differences grew larger as water usage decreased.

A comprehensive evaluation of monochloramine disinfection on water quality, Legionella and other important microorganisms in a hospital.

Opportunistic pathogens such as Legionella are of significant public health concern in hospitals. Microbiological and water chemistry parameters in hot water throughout an Ohio hospital were monitored monthly before and after the installation of a monochloramine disinfection system over 16 months. Water samples from fifteen hot water sampling sites as well as the municipal water supply entering the hospital were analyzed using both culture and qPCR assays for specific microbial pathogens including Legionella, Pseudomonas spp., nontuberculous Mycobacteria [NTM], as well as for heterotrophic bacteria. Legionella culture assays decreased from 68% of all sites being positive prior to monochloramine addition to 6% positive after monochloramine addition, and these trends were parallel to qPCR results. Considering all samples, NTMs by culture were significantly reduced from 61% to 14% positivity (p<0.001) after monochloramine treatment. Mycobacterium genus-specific qPCR positivity was reduced from 92% to 65%, but the change was not significant. Heterotrophic bacteria (heterotrophic bacteria plate counts [HPCs]) exhibited large variability which skewed statistical results on a per room basis. However, when all samples were considered, a significant decrease in HPCs was observed after monochloramine addition. Lastly, Pseudomonas aeruginosa and Vermamoeba vermiformis demonstrated large and significant decrease of qPCR signals post-chloramination. General water chemistry parameters including monochloramine residual, nitrate, nitrite, pH, temperature, metals and total trihalomethanes (TTHMs) were also measured. Significant monochloramine residuals were consistently observed at all sampling sites with very little free ammonia present and no water quality indications of nitrification (e.g., pH decrease, elevated nitrite or nitrate). The addition of monochloramine had no obvious impact on metals (lead, copper and iron) and disinfection by-products.

Synthesis and characterization of stable lead (II) orthophosphate nanoparticle suspensions.

There is great interest in producing nanoparticles for various applications. The objective of this work was to develop a procedure for reproducibly creating stable lead (Pb) phosphate nanoparticle aqueous suspensions. A stable 5 mg/L Pb-phosphate nanoparticle "stock" suspension was synthesized via chemical precipitation of Pb and orthophosphate in water at pH 7.5 with 4.4 mg soluble PO4/L and 7 mg C/L dissolved inorganic carbon. The stock suspension was subsequently diluted to produce stable 0.10 mg/L Pb "challenge" water suspensions without compromising the nanoparticle size, structure, mineralogy and solubility. Specifically, the hexagonal hydroxypyromorphite nanoparticles had an average diameter of 38 nm based on transmission electron microscopy analysis and an associated Pb solubility of 0.001 mg/L. The properties of the stock suspensions were not impacted by further dilutions, and the challenge water suspensions remained stable for 24 hours. In the context of drinking water, a protocol to produce such a stable Pb nanoparticle challenge water suspension would be very useful in evaluating Pb bioavailability, identifying Pb remediation strategies, and testing filter effectiveness to remove Pb from water.

The removal of ammonia, arsenic, iron and manganese by biological treatment from a small Iowa drinking water system.

Although not regulated in United States drinking water, ammonia has the potential to increase chlorine consumption and cause nitrification problems in the distribution system. Many groundwaters with elevated ammonia are also contaminated with other inorganic analytes such as arsenic, iron, and manganese, all of which have primary or secondary maximum contaminant levels (MCLs). The objective of this work was to demonstrate the effectiveness of an innovative biological treatment process to simultaneously remove ammonia (2.9 mg N per L), arsenic (23 µg L-1), iron (2.9 mg L-1) and manganese (80 µg L-1) from a groundwater source in Iowa. The biological treatment system consisted of an "aeration contactor" followed by a conventional granular media filter. Orthophosphate was also added, as a biological nutrient, at 0.3 mg PO4 per L. Ammonia, manganese, and iron were consistently reduced through the pilot system by 98 to 99%. Complete oxidation of ammonia to nitrate was observed (i.e., no nitrite was released) and arsenic was consistently removed to below the 10 µg L-1 MCL. Ammonia was oxidized by ammonia and nitrite oxidizing bacteria and arsenic by bacteria which converted As(III) in the source water to more readily removable As(V). Iron was presumably oxidized by oxygen during aeration although some biologically assisted oxidation could not be ruled out. As(V) bound iron particles were removed in the filter resulting in effective arsenic (and iron) reduction. A surprising treatment benefit was the effective manganese reduction, the mechanism of which was not so clear, but was attributed to biologically assisted oxidation of Mn(II). While some system acclimation time was necessary to achieve desired ammonia and manganese reductions, acceptable arsenic and iron reductions were observed shortly after start-up.

Patterns of Arsenic Release in Drinking Water Distribution Systems.

Retrospective analysis of 20 water systems from the USEPA's Arsenic Demonstration Program revealed three patterns of arsenic levels at the tap, after arsenic treatment of the source well water. Following an initial destabilization period, Pattern A systems (6/20 with low iron/manganese in source water and plastic piping) had arsenic concentrations that did not change as water traveled to consumer taps (conservative contaminant behavior). Pattern B systems (8/20 with high iron/manganese in source water and iron piping) had consistently higher arsenic concentrations at consumer taps, above the arsenic content of incoming treated water, for months to more than a year after arsenic treatment (non-conservative behavior). Pattern C systems (6/20 with additional occasional arsenic treatment complications) experienced multiple arsenic spikes at consumer taps (non-conservative and unpredictable behavior). These field observations suggest that in some water distribution systems arsenic may linger long after it has been removed at its source.

Electrophoretic mobility of Legionella pneumophila serogroups 1 to 14.

Legionella pneumophila (Lp) is ubiquitous in the aquatic environment and can persist within drinking water distribution systems (DWDS) enabling these systems to serve as a potential source of human infections. Bacterial surface charge, deduced from electrophoretic mobility (EPM), is a well-recognized contributor to microorganism mobility, adherence and interactions with their surrounding environment. In this study, the EPM of 32 Lp strains representing serogroup (sg) 1 to 14 were measured, in 9.15 mM KH2PO4 at pH 8, to understand cell surface properties that may influence their occurrence within DWDS. EPM measurements indicated the charge of Lp varied widely between serogroups with five distinct clusters, from least to most negatively charged: (i) sg1 to 3, 5, and 12; (ii) sg6, 8, and 10; (iii) sg9 and 13; (iv) sg7, 11, and 14; and (v) sg4. The EPM of sg1 and 4 strains were pH dependent; however, values were constant between pH 6 and 9, a range typical of drinking water, suggesting that EPM differences between Lp serogroups could impact their survival within DWDS. Understanding the ecological importance of Lp surface properties (e.g. in mobility, colonization, resistance to disinfectants, etc.) within DWDS would aid in mitigation of health risks associated with this water-based pathogen.

Design and Testing of USEPA'S Flint Pipe Rig for Corrosion Control Evaluation.

The US Environmental Protection Agency's Office of Research and Development designed, fabricated, and installed four pipe rigs in Flint, Mich., to help the city optimize corrosion control. The lead service line (LSL) pipe loops were constructed of polyvinyl chloride pipe and fittings and welded steel channel frames. Each pipe rig consisted of four approximately 4 ft-long sections of 0.75 in. inside diameter lead pipe that were excavated from homes fed by the Flint distribution system. The rigs were operated on a set daily on/off schedule such that a specified amount of water passed through each pipe using a solenoid valve-operated timer system. Solenoid problems resulted in sporadic and enhanced daily flow volume (but no flow rate changes) that prevented restabilization of pipe scales. Lead levels were relatively sporadic and statistically different during this period. After the solenoids were replaced, the lead pipe rigs were successfully conditioned, and lead release with consistent influent water chemistry became relatively stable. Average lead levels across all 16 loops ranged between approximately 2 and 5 µg/L after the solenoid replacement. The lead results were consistent with levels measured from LSLs from homes in the city during sequential sampling efforts.

Copper-silver ionization at a US hospital: Interaction of treated drinking water with plumbing materials, aesthetics and other considerations.

Tap water sampling and surface analysis of copper pipe/bathroom porcelain were performed to explore the fate of copper and silver during the first nine months of copper-silver ionization (CSI) applied to cold and hot water at a hospital in Cincinnati, Ohio. Ions dosed by CSI into the water at its point of entry to the hospital were inadvertently removed from hot water by a cation-exchange softener in one building (average removal of 72% copper and 51% silver). Copper at the tap was replenished from corrosion of the building's copper pipes but was typically unable to reach 200 µg/L in first-draw and flushed hot and cold water samples. Cold water lines had >20 µg/L silver at most of the taps that were sampled, which further increased after flushing. However, silver plating onto copper pipe surfaces (in the cold water line but particularly in the hot water line) prevented reaching 20 µg/L silver in cold and/or hot water of some taps. Aesthetically displeasing purple/grey stains in bathroom porcelain were attributed to chlorargyrite [AgCl(s)], an insoluble precipitate that formed when CSI-dosed Ag(+) ions combined with Cl(-) ions that were present in the incoming water. Overall, CSI aims to control Legionella bacteria in drinking water, but plumbing material interactions, aesthetics and other implications also deserve consideration to holistically evaluate in-building drinking water disinfection.