Legionella is an opportunistic waterborne pathogen that causes Legionnaires\' disease. It poses a significant public health risk, especially to vulnerable populations in health care facilities. It is ubiquitous in manufactured water systems and is transmitted via inhalation or aspiration of aerosols/water droplets generated from water fixtures (e.g., showers and hand basins). As such, the effective management of premise plumbing systems (building water systems) in health care facilities is essential for reducing the risk of Legionnaires\' disease. Chemical disinfection is a commonly used control method and chlorine-based disinfectants, including chlorine, chloramine, and chlorine dioxide, have been used for over a century. However, the effectiveness of these disinfectants in premise plumbing systems is affected by various interconnected factors that can make it challenging to maintain effective disinfection. This systematic literature review identifies all studies that have examined the factors impacting the efficacy and decay of chlorine-based disinfectant within premise plumbing systems. A total of 117 field and laboratory-based studies were identified and included in this review. A total of 20 studies directly compared the effectiveness of the different chlorine-based disinfectants. The findings from these studies ranked the typical effectiveness as follows: chloramine > chlorine dioxide > chlorine. A total of 26 factors were identified across 117 studies as influencing the efficacy and decay of disinfectants in premise plumbing systems. These factors were sorted into categories of operational factors that are changed by the operation of water devices and fixtures (such as stagnation, temperature, water velocity), evolving factors which are changed in-directly (such as disinfectant concentration, Legionella disinfectant resistance, Legionella growth, season, biofilm and microbe, protozoa, nitrification, total organic carbon(TOC), pH, dissolved oxygen(DO), hardness, ammonia, and sediment and pipe deposit) and stable factors that are not often changed(such as disinfectant type, pipe material, pipe size, pipe age, water recirculating, softener, corrosion inhibitor, automatic sensor tap, building floor, and construction activity). A factor-effect map of each of these factors and whether they have a positive or negative association with disinfection efficacy against Legionella in premise plumbing systems is presented. It was also found that evaluating the effectiveness of chlorine disinfection as a water risk management strategy is further complicated by varying disinfection resistance of Legionella species and the form of Legionella (culturable/viable but non culturable, free living/biofilm associated, intracellular replication within amoeba hosts). Future research is needed that utilises sensors and other approaches to measure these key factors (such as pH, temperature, stagnation, water age and disinfection residual) in real time throughout premise plumbing systems. This information will support the development of improved models to predict disinfection within premise plumbing systems. The findings from this study will inform the use of chlorine-based disinfection within premise plumbing systems to reduce the risk of Legionnaires disease.

This work comprehensively demonstrates the ability of heterotrophic bacteria, isolated from a chloraminated system, to decay chloramine. This study non-selectively isolated 62 cultures of heterotrophic bacteria from a water sample (0.002 mg-N/L nitrite and 1.42 mg/L total chlorine) collected from a laboratory-scale reactor system; most of the isolates (93.3%) were Mycobacterium sp. Three species of Mycobacterium and one species of Micrococcus were inoculated to a basal inorganic medium with initial concentrations of acetate (from 0 to 24 mg-C/L) and 1.5 mg/L chloramine. Bacterial growth coincided with declines in the concentrations of chloramine, acetate, and ammonium. Detailed experiments with one of the Mycobacterium sp. isolates suggest that the common mechanism of chloramine loss is auto-decomposition likely mediated by chloramine-decaying proteins. The ability of the isolates to grow and decay chloramine underscores the important role of heterotrophic bacteria in the stability of chloramine in water-distribution systems. Existing strategies based on controlling nitrification should be augmented to include minimizing heterotrophic bacteria.

Utilizing solar light and water matrix components in situ to reduce the chemical and energy demands would make treatment technologies more sustainable for micropollutant abatement in wastewater effluents. We herein propose a new strategy for micropollutant abatement through dissolved organic matter (DOM)-mediated photosensitized activation of monochloramine (NH2Cl). Exposing the chlorinated wastewater effluent with residual NH2Cl to solar irradiation (solar/DOM/NH2Cl process) degrades six structurally diverse micropollutants at rate constants 1.26-34.2 times of those by the solar photolysis of the dechlorinated effluent (solar/DOM process). Notably, among the six micropollutants, the degradation rate constants of estradiol, acetaminophen, bisphenol A, and atenolol by the solar/DOM/NH2Cl process are 1.13-4.32 times the summation of those by the solar/DOM and solar/NH2Cl processes. The synergism in micropollutant degradation is attributed to the generation of reactive nitrogen species (RNS) and hydroxyl radicals (HO·) from the photosensitized activation of NH2Cl. Triplet state-excited DOM (3DOM*) dominates the activation of NH2Cl, leading to the generation of RNS, while HO· is produced from the interactions between RNS and other photochemically produced reactive intermediates (e.g., O2·- and DOM·+/·-). The findings advance the knowledge of DOM-mediated photosensitization and offer a sustainable method for micropollutant abatement in wastewater effluents containing residual NH2Cl.

The indirect chloride-mediated ammonia oxidation encounters challenges in maintaining the effectiveness of metal oxide anodes when treating wastewaters with complex compositions. This study aims to develop a highly stable anode with RuO2-SnO2 coatings for treating an etching effluent from semiconductor manufacturing, which majorly contains NH3 and organic compounds. The RuSnOx/Ti electrode was synthesized using wet impregnation and calcination processes. The metal oxide configuration on Ti plate substrate was tuned by varying the step-dipping process in RuCl3 and SnCl4 baths. A 10-day continuous-flow electrolysis was conducted for studying the ammonia removal and chlorine yield under variable conditions, including detention, pH, current density, and initial ammonia and chloride concentrations. In the RuSnOx coatings, the configuration comprising RuO2 nanorods as the surface layer and an intermediate layer of SnO2 crystallites (by plating Ru3+ for three times to cover one Sn4+ layer, denoted as the Ru3Sn/Ti electrode) exhibited the best durability for acid washing, along with relatively high Faradaic efficiency and low energy consumption. To further improve the treatability of real wastewater (NH3-N = 634 mg L-1, chemical oxygen demand (COD) = 6700 mg L-1, Cl- = 2000 mg L-1, pH 11), the duel-cell electrolyzers were constructed in series under a current density of 30 mA cm-2 and 45 min detention. Ultimately, removals of NH3 and COD reached 95.8% and 76.3%, respectively, with successful limitation of chloramine formation.

This paper highlights the potential to effectively inhibit nitrification and restore chloramine levels using a low copper concentration in a biofilm-affected (surface-to-volume ratio 16 m-1) continuous-flow laboratory-scale chloraminated system. High nitrite and low chloramine containing tanks are always recovered with chlorine \"burn\" by water utilities. The \"burn\" is not only costly and operationally complex, but also compromises the water quality, public health, and customer relations. A laboratory system comprising five reactors connected in series was operated. Each reactor simulated conditions typically encountered in full-scale systems. Low amount of copper (0.1-0.2 mg-Cu L-1) was dosed once per day into nitrified reactors. At any given time, only one reactor was dosed with copper. Not only inhibition of nitrification, chloramine decay associated with bulk water, biofilm and sediments also improved. However, the improvement was quicker and more significant when the influent to the reactor contained a high chloramine and a low nitrite concentration. Ammonia oxidising microbes exhibited resilience when exposed to low copper and chloramine concentrations for an extended period. Chloramine decay due to planktonic microbes and chemical reactions in bulk water decreased more rapidly than decay attributed to biofilm and sediments. The concept \"biostable residual chlorine\" explained how copper and chloramine can inhibit nitrification. Once nitrification was inhibited, the chloramine supplied from upstream effectively continued to suppress downstream nitrification, and this effect lasted more than 50 days even at 22 °C. The findings could be used to develop short-term copper dosing strategies and prevent negative impacts of nitrification and breakpoint chlorination.

Manual flushing of building plumbing is commonly used to address water quality issues that arise from water stagnation. Autonomous flushing informed by sensors has the potential to aid in the management of building plumbing, but a number of knowledge gaps hinder its application. This study evaluates autonomous flushing of building plumbing with online sensor and actuator nodes deployed under kitchen sinks in five residential houses. Online oxidation-reduction potential (ORP) and temperature data were collected for nine weeks during the winter and summer in houses with both free chlorine and chloramine. ORP levels in houses with free chlorine residuals decreased after overnight stagnation. The overnight decrease in ORP was not observed when tap water was automatically flushed for five minutes at 6:00 h every morning. ORP levels in houses with chloramine residuals did not decrease consistently after overnight stagnation, and daily automated flushes did not have an observable effect on the ORP signals. Additional laboratory experiments were carried out to evaluate ORP signals during chlorine decay and after incremental changes in chlorine, as would be expected in building plumbing conditions. Results from the lab and field deployments suggest on-line ORP sensors may be used to detect free chlorine decay due to stagnating water, but are not as effective in detecting chloramine decay. However, field results also suggest ORP may not respond as expected on a timely manner after free chlorine or chloramine have been restored, hindering their applicability in developing control algorithms. In this paper we tested twice-daily five-minute automatic flushing and found that it counteracts water quality degradation associated with overnight stagnation in free chlorine systems. An automatic sensor-based flushing is proposed using online temperature sensor data to determine when flushing has reached water from the main. The results suggest that flushing informed by temperature sensors can reduce the flushing time by 46 % compared to the preset five-minute static flush.

Periodontitis is a bacterial-induced disease and for this reason controlling the microbiota is a necessity. Therapy includes self-performed daily oral hygiene in combination with supra- and sub-gingival instrumentation. An adjunctive antimicrobial agent may improve the outcome.
OBJECTIVE: To assess whether a chloramine (Perisolv®) has an adjunctive effect to non-surgical periodontal therapy and whether non-surgical periodontal therapy affects quality of life.
METHODS: Thirty-eight patients were randomized to a test or a control group. Clinical indices were performed at baseline and at three and twelve months. In the test group, Perisolv® was applied initially and after the sub-gingival instrumentation in pathological pockets. Oral health-related quality of life was measured with the Oral Health Impact Profile (OHIP) instrument at baseline and twelve months.
RESULTS: In both groups, an initial probing pocket depth (PPD) of > 4 mm and bleeding on probing (BOP) were statistically reduced (p < 0.002 and p < 0.002 respectively) at twelve months and after adjustment for Bonferroni. There were no significant differences between the test and the control group in terms of the number of PPD, BOP or plaque index, or in the mean OHIP score.
CONCLUSIONS: Chloramine did not have an adjunctive effect, but the overall therapy was significantly efficacious both clinically and in terms of quality of life.
BACKGROUND: Registered at www.
RESULTS: gov:NCT05757921.

Fecal shedding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by infected persons into wastewater was documented early during the COVID-19 pandemic, thereby stimulating inquiries into the effectiveness of municipal wastewater treatment processes for the reduction of infectious viruses. In wastewater treatment plants, free chlorine has traditionally been the disinfectant utilized due to its low cost and high efficacy. However, regulations limiting disinfection by-products have prompted a shift to chloramination in many areas of the United States. While studies regarding the effectiveness of free chlorine against many viral agents are abundant, the efficacy of monochloramine (NH2Cl) has been less well researched. This study aimed to determine the effectiveness of pre-formed monochloramine for disinfection of human coronavirus 229E (HCoV-229E) in both phosphate-buffered saline (PBS) and reclaimed water from a water reclamation plant in Tucson, Arizona. Reclaimed water was sampled over the course of six months (August 2020 to November 2020), and dosed with monochloramine at 3 mg/L. An additional 1 mg/L free ammonia was added to simulate the operational conditions of the treatment plant. Viability was determined using MRC-5 host cell monolayers, using the TCID50 assay method. An average Ct99.9 (concentration of disinfectant multiplied by the contact time to achieve a 99.9 % reduction of the target organism) of 176 mg*min/L monochloramine was determined. No significant difference in inactivation rate was observed between the dosed reclaimed water and phosphate buffered saline (PBS). These data indicate that monochloramine is an effective disinfectant for coronaviruses. They also indicate that the water matrix type did not significantly impact the disinfection efficacy of monochloramine against HCoV-229E in reclaimed wastewater compared to PBS.

Advanced oxidation processes (AOPs) are a key step in eliminating persistent micropollutants in potable reuse trains. Under such conditions, chloramines are an inevitable component in the AOP feed water given their application as an antifouling agent for the upstream membrane processes. In cases when other oxidants, such as free chlorine, are to be used in the AOP treatment, the effect of background chloramines and any potential interplays between the oxidants should be considered. In this study, vacuum-UV (VUV) and VUV/Cl2 have been proposed as promising AOP alternatives for potable reuse and the effect of chloramine photolysis has been considered on the removal of 1,4-dioxane. Results indicated that while presence of chloramine reduces the treatment efficiency in the VUV AOP, coexistence of free chlorine and chloramine oxidants significantly improves 1,4-dioxane degradation rates. Experimental data and kinetic modeling both confirmed the roles of OH• and Cl2•- in 1,4-dioxane removal with 62.5% and 32.5% contribution in the VUV/Cl2/chloramines, respectively. Among the other water matrix conditions, Cl- was shown to improve the degradation rates while HCO3- suppressed the reactions by scavenging radical species. Overall, the findings of this research are informative for the design and development of VUV AOPs at small scale potable reuse facilities.

A rising outbreak of waterborne diseases caused by global warming requires higher microbial stability in the drinking water distribution system (DWDS). Chloramine disinfection is gaining popularity in this context due to its good persistent stability and fewer disinfection byproducts. However, the microbiological risks may be significantly magnified by ammonia-oxidizing bacteria (AOB) in distribution systems during global warming, which is rarely noticed. Hence, this work mainly focuses on AOB to explore its impact on water quality biosafety in the context of global warming. Research indicates that global warming-induced high temperatures can directly or indirectly promote the growth of AOB, thus leading to nitrification. Further, its metabolites or cellular residues can be used as substrates for the growth of heterotrophic bacteria (e.g., waterborne pathogens). Thus, biofilm may be more persistent in the pipelines due to the presence of AOB. Breakpoint chlorination is usually applied to control such situations. However, switching between this strategy and chloramine disinfection would result in even more severe nitrification and other adverse effects. Based on the elevated microbiological risks in DWDS, the following aspects should be paid attention to in future research: (1) to understand the response of nitrifying bacteria to high temperatures and the possible association between AOB and pathogenic growth, (2) to reveal the mechanisms of AOB-mediated biofilm formation under high-temperature stress, and (3) to develop new technologies to prevent and control the occurrence of nitrification in drinking water distribution system.