Tag Archives: chlorination

Sulfaquinoxaline Transformation by Chorine and UV

Nassar R, Mokh S, Rifai A, Chamas F, Hoteit M, Al Iskandarani M. Transformation of sulfaquinoxaline by chlorine and UV light in water: kinetics and by-product identification. Environ Sci Pollut Res Int. 2017 Dec 1. doi: 10.1007/s11356-017-0814-4.

Sulfaquinoxaline (SQX) is an antimicrobial of the sulfonamide class, frequently detected at low levels in drinking and surface water as organic micropollutant. The main goal of the present study is the evaluation of SQX reactivity during chlorination and UV irradiations which are two processes mainly used in water treatment plants. The SQX transformation by chlorination and UV lights (254 nm) was investigated in purified water at common conditions used for water disinfection (pH = 7.2, temperature = 25 °C, [chlorine] = 3 mg L-1). The result shows a slow degradation of SQX during photolysis compared with chlorination process. Kinetic studies that fitted a fluence-based first-order kinetic model were used to determine the kinetic constants of SQX degradation; they were equal to 0.7 × 10-4 and 0.7 × 10-2 s-1 corresponding to the half time lives of 162 and 1.64 min during photolysis and chlorination, respectively. In the second step, seven by-products were generated during a chlorination and photo-transformation of SQX and identified using liquid chromatography with electrospray ionization and tandem mass spectrometry (MS-MS). SO2 extrusion and direct decomposition were the common degradation pathway during photolysis and chlorination. Hydroxylation and isomerization were observed during photodegradation only while electrophilic substitution was observed during chlorination process.

Taste Detection and Acceptability for Chlorine Residual, Bangladesh

Crider Y, Sultana S, Unicomb L, Davis J, Luby SP, Pickering AJ. Can you taste it? Taste detection and acceptability thresholds for chlorine residual in drinking water in Dhaka, Bangladesh. The Science of the total environment. 2017 Sep 20;613-614:840-846. doi: 10.1016/j.scitotenv.2017.09.135.

Chlorination is a low-cost, effective method for drinking water treatment, but aversion to the taste or smell of chlorinated water can limit use of chlorine treatment products. Forced choice triangle tests were used to evaluate chlorine detection and acceptability thresholds for two common types of chlorine among adults in Dhaka, Bangladesh, where previous studies have found low sustained uptake of chlorine water treatment products. The median detection threshold was 0.70 mg/L (n=25, SD=0.57) for water dosed with liquid sodium hypochlorite (NaOCl) and 0.73mg/L (n=25, SD=0.83) for water dosed with solid sodium dichloroisocyanurate (NaDCC). Median acceptability thresholds (based on user report) were 1.16 mg/L (SD=0.70) for NaOCl and 1.26mg/L (SD=0.67) for NaDCC. There was no significant difference in detection or acceptability thresholds for dosing with NaOCl versus NaDCC. Although users are willing to accept treated water in which they can detect the taste of chlorine, their acceptability limit is well below the 2.0mg/L that chlorine water treatment products are often designed to dose. For some settings, reducing dose may increase adoption of chlorinated water while still providing effective disinfection.

Chloroanisole Formation During Drinking Water Chlorination

Zhang K, Zhou X, Zhang, Mao M, Li L, Liao W. Kinetics and mechanisms of formation of earthy and musty odor compounds: Chloroanisoles during water chlorination. Chemosphere. 2016 Aug 22;163:366-372. doi: 10.1016/j.chemosphere.2016.08.051.

Chloroanisoles are often reported as off-flavor compounds which produce an earthy and musty flavors and odors in drinking water. To improve understanding and ultimately minimize the formation of 2,4-dichloroanisole (2,4-DCA), 2,6-dichloroanisole (2,6-DCA) and 2,4,6-trichloroanisole (2,4,6-TCA), which have low odor threshold concentrations (OTC: 0.03-4 ng L-1), a kinetic database for the chlorination of anisole was established by kinetic measurements. The results showed that HOCl reacted with anisole in acidic solution, with the hydrogen ion as an important catalyst. Quantification of product distribution of the produced chloroanisoles demonstrated that a chlorine attack in the para-position was favored over the ortho-position. A kinetic model was formulated, which permitted investigation of the relative importance of the chlorine dose and other water quality parameters including the concentrations of anisole and several metal ions, as well as temperature, on the product distribution of chloroanisoles. In general, high chlorine doses led to low concentrations of intermediates. The presence of ions such as Fe3+ and Al3+ facilitated the formation of chloroanisoles, but Zn2+ and Mn2+ did not. The kinetic model can be applied to optimize water chlorination and minimize earthy and musty odors.

Bacterial Repopulation of Drinking Water Pipe Walls After Chlorination

Mathieu L, Francius G, El Zein R, Angel E, Block JC. Bacterial repopulation of drinking water pipe walls after chlorination. Biofouling. Biofouling. 2016 Sep;32(8):925-34. doi: 10.1080/08927014.2016.1212989/

The short-term kinetics of bacterial repopulation were evaluated after chlorination of high-density polyethylene (HDPE) colonized with drinking water biofilms and compared with bare HDPE surfaces. The effect of chlorination was partial as a residual biofilm persisted and was time-limited as repopulation occurred immediately after water resupply. The total number of bacteria reached the same levels on both the bare and chlorinated biofilm-fouled HDPE after a seven-day exposure to drinking water. Due to the presence of a residual biofilm, the hydrophobicity of chlorinated biofilm-fouled surface exhibited much lower adhesion forces (2.1 nN) compared to bare surfaces (8.9 nN). This could explain the rapid repopulation after chlorination, with a twofold faster bacterial accumulation rate on the bare HDPE surface. γ-Proteobacteria dominated the early stages of repopulation of both surfaces and a shift in the dominance occurred over the colonization time. Such observations define a timescale for cleaning frequency in industrial environments and guidelines for a rinsing procedure using drinking water.

Colonial Microcystis Cells Resistant to Chlorine Oxidation

Fan J, Rao, Chiu YT, Lin TF. Impact of chlorine on the cell integrity and toxin release and degradation of colonial Microcystis. Water Research. 2016 Jun 29;102:394-404. doi: 10.1016/j.watres.2016.06.053.

The occurrence of toxic cyanobacteria in drinking water sources is problematic for water authorities as they can impair drinking water quality. Chlorine as a commonly used oxidant in water treatment plants has shown the potential to lyse cyanobacterial cells, resulting in the release of secondary metabolites which are hard to be removed during conventional water treatment processes. The majority of cyanobacterial species such as Microcystis, often occur in colonial forms under natural conditions. However, previous studies have mainly focused on the influence of chlorination on individual cyanobacterial cells due to technique limitations. A syringe dispersion method combined with a fluorescence technique (SYTOX Green stain with flow cytometry), was successfully developed for the evaluation of cell integrity of colonial Microcystis. Chlorination of Microcystis-laden water was conducted at different chlorine dosages for different colonial sizes (<37, 37-270 and 270-550 μm). The results indicated that colonial Microcystis cells were more resistant to chlorine oxidation than individual cells, which may be attributed to protection from the cell-bound mucilage. There was a lag phase before cell rupture occurred and a Delayed Chick Watson Model describes the experimental data very well for the kinetics of cyanobacterial cell rupture. The growing colonial size caused increases in the lag phases but decreases in the cell lysis rates. Chlorination also induced the release of microcystins (MCs) from colonial Microcystis cells. In particular, increased levels of dissolved MCs were observed in Cheng Kung Lake (CKL) water. In summary, the reaction of chlorine with colonial cyanobacteria is more complicated than with individual cells. The efficiency of chlorine oxidation could be reduced by the cell-bound mucilage and natural water matrix. These observations may provide insights for water authorities to assess the risk to drinking water quality posed by chlorination under natural conditions.

Did Point-of-Use Chlorination Increase During a Cholera Epidemic?

McLennan, J.D. Original Research: Did point-of-use drinking water strategies for children change in the Dominican Republic during a cholera epidemic?  Public Health Nov 2015

Objective: Point-of-use (POU) strategies to improve drinking water, particularly chlorination, are promoted within cholera epidemics when centrally delivered safe drinking water is lacking. Most studies examining POU practices during cholera epidemics have relied on single cross-sectional studies which are limited for assessing behavioural changes. This study examined POU practices in a community over time during a cholera outbreak. 

Study design: Secondary data analysis of existing dataset. 

Methods: During attendance at well-baby clinics serving a low-income peri-urban community in the Dominican Republic, mothers had been routinely asked, using a structured questionnaire, about POU strategies used for drinking water for their children. Frequency distribution of reported practices was determined over a 21 month period during the cholera outbreak on the island of Hispaniola.

Results: An estimated 27.8% of children were reported to have had some exposure to untreated tap water. Unsustained reductions in exposure to untreated tap water were noted early in the epidemic. POU chlorination was infrequent and showed no significant or sustained increases over the study time period.

Conclusion: High reliance on bottled water, consistent with national household patterns prior to the cholera outbreak, may have reduced the perceived need for POU chlorination. Examination of the safety of relying on bottled water during cholera outbreaks is needed. Additionally, further inquiries are needed to understand variation in POU practices both during and beyond cholera outbreaks.

Chlorine addition to household drinking water was infrequent in the study community. No sustained water improvement practices were detected during a cholera outbreak. Extensive pre-existing bottled water use may have contributed to the lack of change.

Free Chlorine Decay in Water Distribution

Zheng M, He C, He Q. Fate of free chlorine in drinking water during distribution in premise plumbing. Ecotoxicology. 2015 Sep 25.

Free chlorine is a potent oxidizing agent and has been used extensively as a disinfectant in processes including water treatment. The presence of free chlorine residual is essential for the prevention of microbial regrowth in water distribution systems. However, excessive levels of free chlorine can cause adverse health effects. It is a major challenge to maintain appropriate levels of free chlorine residual in premise plumbing. As the first effort to assessing the fate of chlorine in premise plumbing using actual premise plumbing pipe sections, three piping materials frequently used in premise plumbing, i.e. copper, galvanized iron, and polyvinyl chloride (PVC), were investigated for their performance in maintaining free chlorine residual. Free chlorine decay was shown to follow first-order kinetics for all three pipe materials tested. The most rapid chlorine decay was observed in copper pipes, suggesting the need for higher chlorine dosage to maintain appropriate levels of free chlorine residual if copper piping is used. PVC pipes exhibited the least reactivity with free chlorine, indicative of the advantage of PVC as a premise plumbing material for maintaining free chlorine residual. The reactivity of copper piping with free chlorine was significantly hindered by the accumulation of pipe deposits. In contrast, the impact on chlorine decay by pipe deposits was not significant in galvanized iron and PVC pipes. Findings in this study are of great importance for the development of effective strategies for the control of free chlorine residual and prevention of microbiological contamination in premise plumbing.