Search

The persistence of high consequence public health pathogens in a wastewater treatment system can significantly impact worker safety, as well as the public and downstream water bodies, particularly if the system is forced to shut down the treatment processes. This study utilizes organism viability to compare the persistence of three pathogen surrogates in wastewater using a pilot-scale activated sludge treatment (AST) system, operated to mimic treatment processes of large-scale plants. Bacillus globigii spores, surrogate for Bacillus anthracis, persisted in the AST system for at least a 50-day observation period leading to a possible steady condition far beyond the solid retention time for sludge particles. MS2 bacteriophage, surrogate for Poliovirus and other non-enveloped enteric viruses, was observed for up to 35 days after introduction, which largely and expectedly correlated to the measured solid retention time. Phi-6 bacteriophage, a surrogate for Ebola virus and other enveloped viruses, was detected for no more than 4 days after introduction, even though the AST system was operated to provide three times slower solids removal than for the other surrogates. This suggests Phi-6 is subject to inactivation under AST conditions rather than physical removal. These results may suggest similar persistence for the surrogated pathogens, leading to appropriate consequence management actions. [ABSTRACT FROM AUTHOR]

A dechlorinated drinking water distribution system simulator containing 15-year old unlined iron pipe was contaminated with Bacillus globigii spores. Bulk phase spore density decreased by 1.5-2.0 loglo 5 min after injection and declined by 1.8-3.4 [log.sub.10] after 4 d. Spores were detected on the iron pipe interior at 2 and 22 CFU/[cm.sup.2] after it was decontaminated and disassembled. These results support previous bench-scale studies that show that spores can persist on corroded surfaces in a drinking water environment. Key words: Bacillus, spores, biofilm, adhesion, iron, corrosion, drinking water, free chlorine. Un simulateur de systeme de distribution d'eau potable dechloree comportant un tuyau en fer non double et age de 15 ans a ete contamine par des spores de Bacillus globigii. La densite des spores dans la phase liquide volumique a diminue de 1,5 a 2,0 [log.sub.10] cinq minutes apres l'injecti on et a baisse de 1,8 a 3,4 loglo apres 4 jours. Les spores ont ete detectees a l'interieur du tuyau de fer a 2 et 22 CFU/[cm.sup.2] une fois qu'il a ete decontamine et demonte. Les resultats soutiennent les etudes anterieures a l'echelle du laboratoire qui montrent que les spores peuvent persister sur des surfaces corrodees dans un environnement d'eau potable. Mots-cles : Bacillus, spores, biofilm, adhesion, fer, corrosion, eau potable, chlore libre. [Traduit par la Redaction], Introduction Research studies examining the persistence of biological agents on drinking water distribution infrastructure have frequently been performed with bench-scale devices (Camper et al. 1996; Morin et al. 1996; Armon [...]

Efforts aimed at reducing pollutant loads from combined sewer overflows (CSOs) on the Muddy Creek receiving waters in Cincinnati, Ohio have been underway in recent years. This includes an investigation of the treatment performance of a flow-through wet weather treatment facility (WWTF) using off-line sedimentation tanks, fine screening and chemical disinfection (disinfection was inactive during this study). Calculations using hydrographs and water quality samples collected at the WWTF during rain events established the mass of biochemical oxygen demand [(BOD).sub.5], chemical oxygen demand, and total suspended solids (TSS) removed. Ten storm events sampled from January to September 2002 helped characterize pollutant removal efficiencies for flow-through treatment. Pollutant removal was classified into four components: flow to the wastewater treatment plant (WWTP), sedimentation, storage, and screening. Most pollutant removal was achieved through settling and storage in the treatment tanks, with removal efficiencies of 20-50% for BOD5 and 25-70% for TSS commonly observed. Owing to the high pollutant load in the early portion of the CSO hydrograph, first-flush containment, or capturing and conveying the early portion of the runoff event to the WWTP, was the most efficient treatment method for every storm investigated. CE Database subject headings: Combined sewer overflow; Sedimentation tanks; Storage tanks; Water pollution; Wastewater management; Ohio; Case reports.

Persistence of Bacillus atrophaeus subsp. globigii spores on corroded iron coupons in drinking water is analyzed by using a biofilm annular reactor. The studies have shown that Bacillus atrophaeus subsp. globigii spores are capable of persisting for an extended time in the presence of high levels of free chlorine.

Disinfecting water generated from a bioterrorism contamination event will require large amounts of disinfectant since the volume of water flushed from a drinking water distribution system or wash water collected from a contaminated outdoor area can accumulate quickly. Commonly used disinfectants may be unavailable in the necessary amounts, so evaluation of alternative disinfectants is needed. This study focuses on disinfection of Bacillus spores in water using acidified nitrite. The effect of varying pH (2 or 3), temperature (5°C or 24°C), nitrite concentration (0.01 or 0.1M), buffer (Butterfields or Phosphate Buffered Saline, PBS) and Bacillus species (B. globigii and B. anthracis Sterne) was evaluated. B. globigii was more resistant to disinfection under all water quality conditions. Disinfection was more effective for B. globigii and B. anthracis Sterne at 0.1M nitrite, pH 2, and 24°C. Disinfection of B. anthracis Sterne was enhanced in low ionic strength Butterfields buffer compared to PBS. [ABSTRACT FROM AUTHOR]

Persistence of Bacillus globigii spores, a surrogate for Bacillus anthracis, was studied on biofouled concrete-lined slides in drinking water using biofilm annular reactors. Reactors were inoculated with B. globigii spores and persistence was monitored in the bulk and biofilm phases, first in dechlorinated water and later with free chlorine concentrations of 1 and 5 mg/L. In the dechlorinated study, a steady state population of spores developed on the slides. The addition of free chlorine at 5 mg/L decreased the adhered spore density by 2-logs within 4 hours and spores were not detected after 67 and 49 hours in the presence of 1 and 5 mg/L free chlorine, respectively. This suggests that adhered spores can persist in non-chlorinated conditions, but detach and/or are inactivated upon addition of free chlorine. When injected into a chlorinated reactor, adhered spore density continually decreased and spores were either undetectable or unquantifiable by 48 hours for both 1 and 5 mg/L chlorine concentrations. Results from these experiments suggest that the presence of a free chlorine residual limits adherence of viable spores to biofouled concrete-lined pipe walls by inactivating spores before they have attached. Both free chlorine concentrations (1 and 5 mg/L) were equally effective at inactivating spores in terms of log reduction, but the higher concentrations yielded faster rates of log reduction. [ABSTRACT FROM AUTHOR]

Persistence of Klebsiella pneumoniae on corroded iron surfaces in drinking water was studied using biofilm annular reactors operated under oligotrophic conditions. Reactors were inoculated with K. pneumoniae, and persistence was monitored in the bulk and biofilm phases. Initial cell concentration of 106 MPN/mL in the bulk water phase resulted in significantly longer adhesion than initial concentrations 1 and 2 orders of magnitude lower. K. pneumoniae cultured in low nutrient growth medium persisted longer in dechlorinated tap water than those cultured in full strength medium. Cell surface charge was more negative under low nutrient conditions, and this influenced electrostatic attraction between the cells and the oxidized iron surface. Cells grown in full strength media persisted longer in water with both low (<0.2 mg/L) and high (>0.5 mg/L) free chlorine residuals. Growth media injected with the cells dechlorinated the water allowing adhesion without inactivation. Microelectrode measurements showed a 40 70% drop in free chlorine from the bulk to the coupon surface, which decreased disinfectant potency against adhered cells. Growth and injection conditions clearly influenced cell adhesion and persistence, but permanent colonization of the corroded iron surface by K. pneumoniae was not observed. [ABSTRACT FROM AUTHOR]

Germination was evaluated as an enhancement to decontamination methods for removing Bacillus spores from drinking water infrastructure. Germinating spores before chlorinating cement mortar or flushing corroded iron was more effective than chlorinating or flushing alone. [ABSTRACT FROM AUTHOR]

Understanding Legionella survival mechanisms within building water systems (BWSs) is challenging due to varying engineering, operational, and water quality characteristics unique to each system. This study aimed to evaluate Legionella, mycobacteria, and free-living amoebae occurrence within a BWS over 18–28 months at six locations differing in plumbing material and potable water age, quality, and usage. A total of 114 bulk water and 57 biofilm samples were analyzed. Legionella culturability fluctuated seasonally with most culture-positive samples being collected during the winter compared to the spring, summer, and fall months. Positive and negative correlations between Legionella and L.pneumophila occurrence and other physiochemical and microbial water quality parameters varied between location and sample types. Whole genome sequencing of 19 presumptive Legionella isolates, from four locations across three time points, identified nine isolates as L. pneumophila serogroup (sg) 1 sequence-type (ST) 1; three as L. pneumophila sg5 ST1950 and ST2037; six as L. feeleii; and one as Ochrobactrum. Results showed the presence of a diverse Legionella population with consistent and sporadic occurrence at four and two locations, respectively. Viewed collectively with similar studies, this information will enable a better understanding of the engineering, operational, and water quality parameters supporting Legionella growth within BWSs. [ABSTRACT FROM AUTHOR]

Building water systems promote the regrowth and survival of opportunistic pathogens, such as Legionella pneumophila, especially within biofilms, where most drinking water microbes reside. However, compared to their planktonic form, disinfection efficacy for the biofilm-associated forms of water-based pathogens is unclear. The aim of this study was to determine the effectiveness of free chlorine and monochloramine in the inactivation of biofilm-associated L. pneumophila strain Philadelphia-1 serogroup 1 (Lp). Mature (1.5-2 y old) drinking water biofilms were developed on copper (Cu) and polyvinylchloride (PVC) slides within biofilm annular reactors, then colonized with Lp at approximately 4 log10 CFU cm-2 and exposed to 2 mg L-1 of free chlorine or monochloramine. Ct (disinfectant concentration x time, expressed as mg min L-1) inactivation values for 2-, 3-, and 4-log10 reduction of planktonic and biofilm Lp were determined. For planktonic Lp, free chlorine was more effective at inactivation compared to monochloramine treatment and for biofilm-associated Lp, monochloramine was more effective on Cu biofilms, while free chlorine was more effective on PVC biofilms. In contrast to monochloramine, free chlorine treatment of Cu and PVC biofilms, negatively impacted Lp 16S rRNA gene transcript levels, and may act synergistically with Cu surfaces to further reduce transcript levels. Moreover, Lp cells shed from biofilms into the bulk water, were more resistant to disinfection compared to prepared planktonic Lp cells. Results from this study indicate that biofilm association, disinfectant type, and substratum play an important role in the survival of Legionella pneumophila in building water systems. [ABSTRACT FROM AUTHOR]