Addition Of Monochloramine Research Articles

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.

Fungal diversity and presence of potentially pathogenic fungi in a hospital hot water system treated with on-site monochloramine

Currently, our knowledge of fungal ecology in engineered drinking water systems is limited, despite the potential for these systems to serve as a reservoir for opportunistic pathogens. In this study, hot water samples were collected both prior to and following the addition of monochloramine as an on-site disinfectant in a hospital hot water system. Fungal ecology was then analyzed by high throughput sequencing of the fungal ITS1 region. The results demonstrate that the genera Penicillium, Aspergillus, Peniophora, Cladosporium and Rhodosporidium comprised the core fungal biome of the hospital hot water system. Penicillium dominated the fungal community with an average relative abundance of 88.89% (±6.37%). ITS1 sequences of fungal genera containing potential pathogens such as Aspergillus, Candida, and Fusarium were also detected in this study. No significant change in fungal community structure was observed before and after the initiation of on-site monochloramine water treatment. This work represents the first report of the effects of on-site secondary water disinfection on fungal ecology in premise plumbing system, and demonstrates the necessity of considering opportunistic fungal pathogens during the evaluation of secondary premise plumbing disinfection systems.

Effect of UV and UV/H2O2 in the Presence of Chloramines on NDMA Formation Potential of Tramadol

This study evaluates the effect of UV-C and UV-C/H(2)O(2) in the presence of chloramines on the N-nitrosodimethylamine formation potential (NDMA FP) of tramadol as a model precursor. The experiments were performed at high initial concentrations of TMDL (i.e., 20 mg/L) in order to elucidate the structures of TMDL byproducts. Twenty-four byproducts were identified in UV-C, UV-C/monochloramine, and UV/H(2)O(2)/monochloramine oxidation of tramadol using MS(3) capabilities of a hybrid quadrupole-linear ion trap mass spectrometer, combined with online hydrogen/deuterium (H/D) exchange experiments. Oxidative cleavage of methoxy and methoxybenzene moiety, O-demethylation, hydroxylation, and cyclohexane ring-opening were identified as major reaction mechanisms of tramadol in UV oxidation. Addition of monochloramine decreased the degradation rates of tramadol and its byproducts and yielded several monochlorinated derivatives. The oxidation rates were significantly enhanced in the presence of H(2)O(2), and byproducts of oxidative benzene ring-opening were detected. The majority of the identified byproducts are likely to have a higher NDMA FP than the parent compound due to a reduced steric hindrance and/or insertion of electron-donating hydroxyl groups in the N,N-dimethylamine side chain. This was confirmed by the results of NDMA FP tests, which showed that the formation of NDMA was enhanced up to four times depending on the process conditions in UV alone and in UV and UV/H(2)O(2) in the presence of monochloramine. Prolonged oxidation by hydroxyl radicals in UV/H(2)O(2)/monochloramine process mineralized some of the byproducts and slightly reduced the NDMA FP at the end of the treatment. The obtained degradation pathway of tramadol allowed the correlation of changes in NDMA FP during oxidation with its major oxidative transformation reactions. This manuscript demonstrates the significance of oxidation byproducts as NDMA precursors and emphasizes the need for their consideration when evaluating the evolution of NDMA FP during oxidative treatment.

Formation of organic chloramines during water disinfection – chlorination versus chloramination

Many of the available studies on formation of organic chloramines during chlorination or chloramination have involved model organic nitrogen compounds (e.g., amino acids), but not naturally occurring organic nitrogen in water. This study assessed organic chloramine formation during chlorination and chloramination of 16 natural organic matter (NOM) solutions and 16 surface waters which contained dissolved organic nitrogen (DON). Chlorination rapidly formed organic chloramines within 10 min, whereas chloramination formed organic chloramination much more slowly, reaching the maximum concentration between 2 and 120 h after the addition of monochloramine into the solutions containing DON. The average organic chloramine formation upon addition of free chlorine and monochloramine into the NOM solutions were 0.78 mg-Cl 2/mg-DON at 10 min and 0.16 mg-Cl 2/mg-DON at 24 h, respectively. Organic chloramine formation upon chlorination and chloramination increased as the dissolved organic carbon/dissolved organic nitrogen (DOC/DON) ratio decreased (i.e., DON contents increased). Chlorination of molecular weight (10,000 Da) fractionated water showed that molecular weight of DON would not impact the amount of organic chloramines produced. Comparison of three different disinfection schemes at water treatment plants (free chlorine, preformed monochloramine, and chlorine/ammonia additions) indicated organic chloramine formation could lead to a possible overestimation of disinfection capacity in many chloraminated water systems that add chlorine followed by an ammonia addition to form monochloramine.

Comparing the effect of various pipe materials on biofilm formation in chlorinated and combined chlorine-chloraminated water systems

To compare the effect of various pipe materials on biofilm formation, surface water was used as the test water source; plastic-based pipe materials (polyvinyl chloride-PVC, unplasticised polyvinyl chloride-UPVC, medium density polyethylene-MDPE) and cement-based pipe materials (cement and asbestos cement) are commonly used in drinking water distribution systems in South Africa as test pipe materials. Disinfection was performed using ca 2.5 mgl-1 initial chlorine followed by ca 1.5mg l-1 monochloramine. The evaluation of the process relied on attached coliforms and heterotrophic plate count bacteria. General data indicated the colonisation of all test pipe materials by micro-organisms under the chlorination process within the first 20 min and over the remainder of the study period. The addition of monochloramine to the chlorinated water system (24 h after chlorination) resulted in the removal of coliforms and heterotrophic bacteria attached to pipe materials. Less than 1 cfu&#3618;&#3607;cm-2 viable bacterium (except for PVC) was observed on the surface of test pipes between 48 and 168 h. However, the factor of time cannot be ignored in determining the effect of pipe materials on biofilm formation in potable water systems. Bacterial regrowth occurred on the surface of all pipe materials between 168 and 672 h. The capability of bacterial regrowth occurring on the surface of test pipe materials during this period was linked to the depletion of the concentration of monochloramine residual. Statistical evidence showed that the generic type of pipe materials greatly influenced the density of bacteria in laboratory-scale systems. Cement-based materials significantly supported less fixed bacteria than plastic-based materials (at p

Effect of a combined chlorine-monochloramine process on the inhibition of biofilm regrowth in potable water systems

To investigate the effect of a combined chlorine-monochloramine disinfection process on the inhibition of biofilm regrowth, surface water and groundwater were used as the test water sources while stainless steel and galvanized mild steel were used for the study of biofilm regrowth in a laboratory-scale unit. Disinfection was carried out using 2.5 mg.L-1 chlorine followed by 1.5 mg.mg.L-1 monochloramine. The bactericidal effectiveness of the process relied on heterotrophic plate count (HPC) and total bacteria. The concentrations of organic and inorganic compounds such as dissolved organic carbon, calcium, magnesium, chemical oxygen demand, total nitrogen, phosphate and sulfate were also taken into account. The formation of biofilm occurred 24 h after the exposure of test pipe materials to both chlorinated surface water and groundwater (with the average counts of 2 log.cfu.cm-2 for viable bacteria in both systems, 5 log.cells.cm-2 and 6 log.cells.cm-2 in surface water and groundwater systems respectively). A concentration of 0.45 ± 0.5 mg.L-1 free chlorine could not inhibit the formation of biofilm on the surface of pipe materials. Whereas the yield for attached bacteria was initially similar under chlorination treatment (24 h after chlorination), a significant difference in bacterial biofilm counts occurred in chlorinated water systems with the addition of monochloramine. Less than one attached viable and total bacteria colonized slides exposed to both combined chlorine-monochloramine surface water and groundwater systems. This same pattern was detected up to 7 d and 21 d on the surface of test pipe materials exposed to surface water and groundwater respectively. The present study demonstrates the inability of bacteria to colonize surfaces of stainless steel and galvanized mild steel in the combined chlorine-monochloramine system. In such a treatment the susceptibility of attached viable bacteria was observed only when the concentration of monochloramine persisted up to 0.35 mg.L-1 and 0.2 mg.L-1 in surface water and groundwater respectively. A lower monochloramine residual of 0.15 mg.L-1 led to the phenomenon of biofilm regrowth. Because the residual monochloramine depleted earlier in the groundwater system than in the surface water system, biofilm inhibition lasted longer in the latter system than in the former. A LSD test showed no significant difference in attached bacterial counts (at p &amp;lt; 0.05) when chlorine was used as primary disinfectant and monochloramine as second disinfectant for the disinfection of surface water and groundwater. Although the high concentrations (average) of organic (Surface water: DOC = 5.55 mg.L-1, groundwater: DOC = 12.6 mg.L-1 and inorganic compounds (surface water: Ca2+ = 12.17 mg.L-1, Mg2+ = 9.20 mg.L-1, COD = 11.35 mg.L-1, N = 2.70, SO43- = 21.40 mg.L-1, PO43- = 0.4 mg.L-1 = 0.54 groundwater: Ca2+ = 57.13 mg.L-1, Mg2+ = 77 mg.L-1, COD = 7.14 mg.L-1, N = 9.02, SO43- = 69.25 mg.L-1, PO43- = 0.4 mg.L-1) could influence bacterial biofilm regrowth in treated water systems, statistical data supported the findings that a combined chlorine-monochloramine process and the persistence of monochloramine in the combined systems constitutes one of the most important factors linked to the inhibition of bacterial biofilm in a drinking water system.

The photochemical addition of monochloramine to cyclohexene

The photochemical addition of monochloramine to cyclohexene in ether at 0° and −40° resulted in the 1:1 adduct, trans-2-chlorocyclohexylamine, together with trans-1,2-dichlorocyclohexane, rans-2-chlorocyclohexanol, 3-chlorocyclohexene, hexanenitrile, 3,3′-bicyclohexenyl and ammonium chloride. The effects of the reaction conditions on the best yield of trans-2-chlorocyclohexylamine (8·2%) was studied. The lower initial concentration of the reactants and the lower reaction temp are effective in raising the yield. A probable reaction scheme leading to the observed products is discussed.