Residual Chlorine Research Articles

The mixed-order chlorine decay model with an analytical solution and corresponding trihalomethane generation model in drinking water

Ensuring effective drinking water disinfection, remaining a certain amount of residual chlorine, and controlling disinfection by-product formation were very important for guarantying water quality safety and protecting public health; thus, the chlorine decay model and corresponding disinfection by-product formation model were necessary. This paper proposed a mixed-order chlorine bulk decay model (two parameters) based on Taylor's formula and derived its analytical solution. The accuracy of the mixed-order model was evaluated by comparing it with the nth-order model. To optimize the model and reduce the number of parameters required to be calibrated, the relationship of parameters with temperature, initial chlorine concentration, TOC and inorganic substance (ammonia nitrogen and iodide ion) was explored. The result proved that one of the parameters could be regarded as temperature dependent only. Meanwhile, the temperature equation of the model parameters was established by the Arrhenius formula. Subsequently, this paper selected trihalomethane as the target and study the linear relationship between chlorine consumption and trihalomethane formation. The results indicated that the liner slope had little correlation with initial chlorine concentration and temperature. On this basis, the corresponding trihalomethane model was built and its performance was proven to be good. The modeling developed in this work could be applied to drinking water distribution systems for residual chlorine and trihalomethane prediction, and provided a reference for the decision involving water quality.

Modifications to sorption and sinking capability of microplastics after chlorination

Abstract Chlorination disinfection in water treatments may be highly destructive to microplastics (MPs). Herein, low- and high-dose (concentration–time values at 75 and 9,600 mg min L−1, respectively) chlorination processes were used to simulate short-term chlorination in drinking water treatment plants and long-term residual chlorine reaction in drinking water supply systems, respectively. Both chlorination processes induced modifications to polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC) MPs, varying in polymer types and sizes. Oxidized and chlorinated bonds were detected, and destructed surfaces with increased specific surface area and reduced hydrophobicity were observed. As a result, the sorption capacity of all MPs was weakened, e.g., low-dose chlorination (pH 7) depressed the sorption of ciprofloxacin by 6.5 μm PE (Kf from 0.140 to 0.128 L g−1). The sinking behavior of PET, PS, and PVC MPs was enhanced, e.g., the sinking ratio of 200 μm PET increased by ∼30% after low-dose chlorination (pH 7). By contrast, PE tended to float after high-dose chlorination. Furthermore, chlorination of MPs generated various products, which were the degraded fragments from the MP skeleton. In general, chlorination disinfection reduces the potential of MPs as transport vectors of organic contaminants.

UV Disinfection Systems for Wastewater Treatment: Emphasis on Reactivation of Microorganisms

UV disinfection is cost-effective and easy to maintain for decentralized areas. However, to ensure its effectiveness, some parameters need to be considered. In this study, a general search of Web of Science articles was performed to determine the possible influence of these parameters on the reactivation of microorganisms in UV systems; in addition, different search strings were used focusing exclusively on wastewater treatment, UV systems and Advanced Oxidation Processes (AOPs). It was found that in order to maintain low transmittance, it is essential to remove suspended solids and reduce water hardness. It is recommended to control the zeta potential in the range of 0–5 mV to avoid the aggregation of particles and bacteria. Determining the appropriate UV dose is essential to mitigate the reactivation of microorganisms. A minimum dose of 40 mJ/cm2 can contribute to effective disinfection and reduce the likelihood of reactivation. In addition, maintaining a residual chlorine level of at least 0.5 mg/L provides an additional barrier to reactivation. It is also important to optimize the design flow rate of the UV system as recommended for each individual unit. These measures, together with the combination of UV disinfection and chemical or AOPS, can effectively reduce the reactivation.

Evaluation of Drinking Water Quality and Treatment from Coolers in Public Places in Madinah City, Saudi Arabia

The aim of this work is to prevent the public drinking from water coolers, by using an auto-detection process, if the quality of water is low. Therefore, the proposed water treatment management system for allows the activation of dispensers to provide the best-quality water coolers. The objective is to investigate the quality of the drinking water from coolers in public places in Madinah and to provide clean, safe, and healthy drinking water for the general public. The methodology consisted of performing different analyses, tests, and water treatments, such as physicochemical analyses of the water samples, measurements of the different concentrations of anions, measurements of the concentrations of heavy metals, and bacteriological tests of the water samples. Therefore, 66 water samples were tested, and the experimental values were compared with the reference values given by the World Health Organization (WHO) and Saudi Standards, Metrology, and Quality Organization (SASO) for drinking water. The tests revealed that the physicochemical parameters (pH, EC, TDS, and TH) of different water sources (95.5%) were in accordance with the SASO and WHO values. In addition, all the analyzed water samples (100%) contained permissible levels of nitrates, sulfates, nitrites, and free residual chlorine, as indicated by the results. However, 68.2% of the samples studied had fluoride concentrations below the standard limits. Furthermore, heavy metals such as lead, iron, and others were tested for all water coolers. The measured findings indicated that just one cooler exceeded the permissible limit of 0.3 mg/L for Fe, and the biological contamination testing revealed that 4.5% of the coolers were infected with coliforms. Finally, this research suggests that water coolers should be regularly maintained. Additionally, using the best design for the water desalination process is very important to give the best drinking water quality.

Assessment of Residual Chlorine Interaction with Different Microelements in Stormwater Sediments.

One consequence of intensive outdoor disinfection using chlorinated compounds is environmental pollution. It has been found that disinfectants are the most effective tool to avoid the spread of infections and viruses. Studies have shown that the use of chlorine-based disinfectants (sodium hypochlorite) leaves residual chlorine and other disinfection byproducts in the environment. They also have harmful effects on, inter alia, water quality, ecosystems, as well as exacerbating the corrosion of surfaces. To meet regulatory standards, monitoring of the presence of residual chlorine in the environment is vitally important. The aim of this study is to analyse the occurrence of residual chlorine in stormwater after outdoor disinfection using sodium hypochlorite and to investigate its interaction with different microelements as well their possible impacts. Stormwater samples collected at permanently disinfected locations were analysed via X-ray absorption spectroscopy. The concentrations of Cl and the following elements Na, Si, K, Ca, Cr, Fe, Ni, Cu, Zn were detected and their relationship with chlorine was determined using the Python programming language. The research presents Cl concentration values (%) that vary from 0.02 to 0.04. The results of the modelling revealed strong correlations between Cl and Fe (value 0.65) and Ca (value -0.61) and the occurrence of CaCl2 and FeCl3. The strong relationship between Cl and Fe explains the significant increase in surface corrosion after disinfection with chlorine-based substances.

Stability of Drinking Water Distribution Systems and Control of Disinfection By-Products.

The stability of drinking water distribution systems and the management of disinfection by-products are critical to ensuring public health safety. In this paper, the interrelationships between corrosion products in the network, microbes, and drinking water quality are elucidated. This review also discusses the mechanisms through which corrosive by-products from the piping network influence the decay of disinfectants and the formation of harmful disinfection by-products. Factors such as copper corrosion by-products, CuO, Cu2O, and Cu2+ play a significant role in accelerating disinfectant decay and catalyzing the production of by-products. Biofilms on pipe walls react with residual chlorine, leading to the formation of disinfection by-products (DBPs) that also amplify health risks. Finally, this paper finally highlights the potential of peroxymonosulfate (PMS), an industrial oxidant, as a disinfectant that can reduce DBP formation, while acknowledging the risks associated with its corrosive nature. Overall, the impact of the corrosive by-products of pipe scale and microbial communities on water quality in pipe networks is discussed, and recommendations for removing DBPs are presented.

Novel ultra-sensitive and highly selective cyanine sensors based on solvent-free microwave synthesis for the detection of trace hypochlorite ions in drinking water

The adoption of chlorine in drinking water disinfection with the determination of residual chlorine in the form of hypochlorite ion (ClO-) is in widespread demand. Several sensors including colorimetric, fluorometric, and electrochemical methods are currently in use, but detection limits and ease of application remain a challenge. In this work, two new cyanine derivatives-based ClO- sensors, that were prepared by solvent-free microwave synthesis, are reported. The two sensors are highly sensitive and selective to ClO-, exhibiting a noticeable color change visible to the naked eye. Additionally, the sensors can detect ClO- without interference from other potential water pollutants, with low detection limits of 7.43 ppb and 0.917 ppb based on absorption performance. When using fluorometric methods, the sensors' detection limits are pushed down to 0.025 ppb and 0.598 ppb for sensors I and II, respectively. The sensors can be loaded with paper strips for field and domestic detection of ClO- in tap water treatment installations. Using the quartz crystal microbalance (QCM) technique, these sensors showed strong detection sensitivity to ClO-, with detection limits of 0.256 ppm and 0.09 ppm for sensors I and II, respectively. Quantum chemical studies using density functional theory (DFT) calculations, natural bond orbital (NBO) analysis, molecular electrostatic potential (MESP), and time-dependent density functional theory (TD-DFT) supported the findings. The sensing mechanism is rationalized in terms of radical cation formation upon ClO- oxidation of cyanine sensors I and II.

Water Quality Index and Human Health Risk Assessment of Drinking Water in Selected Urban Areas of a Mega City.

The present study was conducted to evaluate the quality of drinking water and assess the potential health hazards due to water contaminants in selected urban areas of Lahore, Pakistan. Water samples were collected from ten sites and analyzed for different physico-chemical parameters including turbidity, color, pH, total dissolved solids (TDS), nitrates, fluoride, residual chlorine, and total hardness. Additionally, heavy metal (arsenic) and microbial parameters (E. coli) were also determined in the water samples. Drinking water quality evaluation indices, including the water quality index (WQI) for physico-chemical and biological parameters and human health risk assessment (HHRA) for heavy metal were estimated using the analytical results of the target parameters. It was found in most of the areas that the levels of arsenic, fluoride, TDS, and residual chlorine were higher than those recommended by the National Environmental Quality Standard (NEQS) and World Health Organization (WHO) guidelines. In addition to the physico-chemical parameters, microbial content (E. coli) was also found in the drinking water samples of the selected areas. Statistical analysis of the results indicated that levels of target parameters in drinking water samples are significantly different between sampling sites. The WQI for all physico-chemical and microbial parameters indicated that drinking water in most of the areas was unfit and unsuitable (WQI > 100) for drinking purposes except for the water of Bhatti Gate and Chota Gaon Shahdara with a WQI of 87 and 91, respectively. Drinking water in these areas had a very poor WQI rating. According to HHRA, drinking water from the selected sites was found to be of high risk to children and adults. The carcinogenic risk of arsenic indicated that all samples were of high risk to both adults and children (4.60 and 4.37 × 10-3, respectively). Regular monitoring of drinking water quality is essential, and proactive measures must be implemented to ensure the treatment and availability of safe drinking water in urban areas.

Evaluation of the Performance of the Makhmuor Villages Water Filtration Plant in Nineveh Governorate / Iraq

The current study was conducted to evaluate the performance of the Makhmuor villages water filtration plant and to ensure the validity of the water produced and delivered to the consumer. The physical, chemical and biological properties of the Tigris River water at the intake of the plant and at different stages of the plant and the water reaching the residential areas benefiting from the plant were studied. The studied samples were collected for a period of five months, monthly from July to November 2022. Temperature, electrical conductivity, total dissolved solids, turbidity, dissolved oxygen, biological oxygen demand, total alkalinity, total hardness, calcium, magnesium, chloride, sulfates, phosphates, nitrates, pH, residual chlorine, and the total number of bacteria. And the total number of coli bacteria and the number of plankton. The results of the study showed that many samples conformed to the Iraqi and international specifications for drinking water, except for turbidity, as it exceeded the permissible limit in most samples, which is less than 5 (Nephelometric Turbidity Unit) NTU, and dissolved oxygen reached 4.4 and 4.8 mg / liter in the Tigris River for the month of August and water Liquefaction in the villages for the months of July and September, respectively, as well as 4.4 mg/L in the automated sedimentation and filtration ponds and the village 2 for the month of November. The biological requirement for oxygen in seven samples in different locations for the months of October, August and November was 0.1 mg/L and the highest value was 6.4 mg/L in basin 2 in October. And nitrates were in low concentrations. As for residual chlorine, all tests were free of any percentage of it, except for the month of November, when it was in the plant tank 2 mg / liter and in the two villages 0.3 mg / liter. Thus, the number of bacteria increased and appeared in all samples throughout the study period.

Environmental, social, and WASH factors affecting the recurrence of cholera outbreaks in displacement camps in Northeast Nigeria: a rapid appraisal

Abstract In 2021, Nigeria witnessed a severe cholera outbreak that affected Borno state, in which more than 1,600,000 internally displaced persons (IDPs) resided at the time. This rapid appraisal explored factors that facilitate the recurrence of cholera outbreaks in sites hosting IDPs in Northeast Nigeria. Semi-structured interviews were conducted with water, sanitation, and hygiene (WASH), management, and healthcare personnel working in ten displacement camps in Borno state. The interviews were complemented by transect walks and field observations, measurements of free residual chlorine levels, and publicly available data published by the International Organization for Migration Displacement Tracking Matrix. The recurrence of cholera outbreaks appears to be facilitated by substantial interactions between IDPs and host communities, and suboptimal WASH services in camps. Of particular concern, IDP camps are exposed to extreme weather-related events that damage facilities and subsequently affect WASH practices. WASH services in camps may likewise be severely hindered by an influx of new arrivals. In conclusion, we emphasize the importance of expanding WASH activities to host communities and developing site-specific WASH interventions and chlorination targets. Practical recommendations are needed for the prevention and control of outbreaks following extreme weather-related events and population influxes.

English

Drinking water quality is a critical factor affecting human health particularly in natural resource-dependent countries including Nigeria. Hydrocarbon related pollution, mining waste, microbial load, industrial discharge and other anthropogenic stressors degrade drinking water quality in coastal communities and pose serious public health and ecological risks. This study evaluated the physicochemical properties of drinking water in selected communities (Okerenkoko, Kurutie, and Oporoza) located in Gbaramatu Kingdom, in the Niger Delta region of Nigeria, in order to assess the water quality using the Water Quality Index (WQI) and pollution models. Nitrate, Chromium, Cadmium, Copper, Lead, Aluminium, pH, Total Hardness, Total Dissolved Solids, Cyanide, and Residual Chlorine were measured in twelve selected locations across the three communities.  The WQI results of the analyzed water samples in the area indicated that they exceeded the critical WQI value of 100, with a mean pH of 8.11 ± 0.32, indicating unsuitability for consumption. Nickel ranging from 0.014 to 0.176 mg/L and residual chlorine 11.6 to 7407 mg/L were the major contributors to the degradation of water quality and exceeded the WHO recommended limit of 0.02 and 0.25 respectively. While groundwater had better organoleptic properties compared to surface and rain water, the geo-accumulation index showed that water sources in the area vary from moderately to heavily contaminated with Ni and Cd. These WQI and pollution model results necessitate an urgent response from local stakeholders to address the water quality deterioration, such as providing alternative water supplies, to minimize the potential health risks to the local population.   Key words: Water quality index, contamination index, oil pollution, chemical parameters, geo-accumulation index.

Process of Quality Control of Bottled Water at PT. Tirta Purbalingga Adijaya, Bogor

Quality control is important in the drinking water production process. Drinking water sourced from nature, of course, contains a variety of minerals, ions, and even microorganisms, so it needs to be processed first so that it meets the needs of the human body and is safe for consumption. PT. Tirta Purbalingga Adijaya, Bogor in producing bottled drinking water refers to SNI 3553: 2015 concerning requirements for drinking water quality, as well as in processing it refers to the Regulation of the Minister of Health No.32 of 2017 concerning Standards for Quality Standards for Environmental Health and Water Health Requirements for Sanitation Hygiene Purposes , Swimming Pools, Solus Per Aqua, And Public Baths. PT. Tirta Purbalingga Adijaya, Bogor implements the Hazard Analysis Critical Control Point (HACCP) system where both raw water, processing and finished products are quality controlled every hour by water treatment operators and the results are verified by Quality Control analysts. Important things that become critical control points are filtering with carbon filters and ozone injection. If these two things are not controlled, it will affect the quality content of the drinking water produced and cause hazards such as residual chlorine and microbial contamination so that the product does not meet standards and cannot be marketed. The tests carried out were physical tests such as organoleptic tests, chemical tests such as chlorine content, ozone, metals and others as well as microbiological tests such as total microbes, fungi, coliform and pseudomonas aeruginosa. Based on the analysis that was carried out for 1 week on January 9-14 2023, it was concluded that the Prim-A brand bottled drinking water produced by PT. Tirta Purbalingga Adijaya, Bogor has met the standards set in Indonesia and is safe for human consumption.

Analisis Kualitas Air Permukaan Sungai Brantas Berdasarkan Parameter Fisik dan Kimia

The Brantas River is a river that plays an important role in supplying the largest raw material for drinking water in the East Java region. Raw water sourced from the Brantas River must have gone through a proper water treatment process and must comply with the requirements for drinking water quality standards stipulated in Permenkes No. 492 of 2010 concerning Drinking Water Quality Requirements. This study aims to determine the surface water quality of the Brantas River based on measurements of physical parameters (turbidity, temperature, DHL, and TDS) and chemical parameters (pH, and residual chlorine) before and after the water treatment process. This study uses a quantitative method on the basis of observation. The research subjects taken were data measuring surface water parameters of the Brantas River from April 2022 to March 2023 before and after the water treatment process. The results showed that there was a difference in the average value before and after the water treatment process for turbidity of 374.8, temperature of 0.06, DHL of 13.5, TDS of 18.58, pH of 0.01, and residual chlorine of 0.27. It is known that all parameters of the surface water of the Brantas River which have gone through a water treatment process meet the drinking water quality standards according to the requirements of Permenkes No. 492 of 2010. And it can be concluded that the quality of drinking water sourced from the surface water of the Brantas River is good and can be distributed to the community.

Assessing the impact of the COVID‑19 pandemic health protocols on the hygiene status of swimming pools of hotel units.

With the onset of the coronavirus disease 2019 (COVID-19) pandemic, numerous countries imposed strict lockdown measures and travel bans, resulting in the closure of hotels. Over time, the opening of hotel units was gradually allowed, and new strict regulations and protocols were issued to ensure the hygiene and safety of swimming pools in the era of COVID-19. The present study aimed to evaluate the implementation of strict health COVID-19-related protocols in hotel units during the 2020 summer tourist season concerning microbiological hygiene and physicochemical parameters of water, and to compare the data with those from the 2019 tourist season. For this reason, 591 water samples from 62 swimming pools were analyzed, of which 381 samples were for the 2019 tourist season and 210 samples were for the 2020 tourist season. To examine the presence of Legionella spp, 132 additional samples were taken from 14 pools, of which 49 in 2019 and 83 in 2020. In 2019, 2.89% (11/381) of the samples were out of legislative limits (0/250 mg/l) regarding the presence of Escherichia coli (E. coli), 9.45% (36/381) were out of acceptable limits (0/250 mg/l) regarding the presence of Pseudomonas aeruginosa (P. aeruginosa) and 8.92% (34/381) had residual chlorine levels <0.4 mg/l. In 2020, 1.43% (3/210) of the samples were out of the legislative limits as regards the presence of E. coli, 7.14% (15/210) were out of acceptable limits regarding the presence of P. aeruginosa and 3.33% (7/210) of the samples measured residual chlorine levels <0.4 mg/l. The risk ratio (RR) in relation to the presence of E. coli due to incorrect compliance with the requirements for residual chlorine was calculated for 2019 at 8.50, while in 2020 it was calculated at 14.50 (P=0.008). The RR of the presence of P. aeruginosa due to inappropriate residual chlorine requirements was calculated in 2019 at 2.04 (P=0.0814), while in 2020 it was calculated at 2.07 (P=0.44). According to the microbiological hygiene and physicochemical parameters of the water samples studied, there was a significant improvement due to the strict protocols for the swimming pools in the summer season of 2020 compared to the tourist season of 2019, namely 72.72% (E. coli), 58.33% (P. aeruginosa), 79.41% (of residual chlorine <0.4 mg/l) in the three main parameters studied. Finally, an increased colonization by Legionella spp. detected in the internal networks of the hotels due to the non-operation of the hotels during the lockdown, the improper disinfection and stagnant water in the internal water supply networks. Specifically, in 2019, 95.92% (47/49) of the samples tested negative and 4.08% (2/49) tested positive (≥50 CFU/l) for Legionella spp., compared to 2020 where 91.57% (76/83) of the samples tested negative and 8.43% (7/83) tested positive.

Localized Corrosion of High-Grade Stainless Steels: Grade Selection in Chlorinated Seawater

Chlorination is widely used in seawater systems to avoid fouling and associated microbial-induced corrosion. Free chlorine is a strong oxidizing agent that prevents biofilm formation on immersed surfaces when used above a certain content. However, the presence of residual chlorine associated with the relatively high chloride content in seawater significantly increases the risk of localized corrosion for most stainless steels. In the present study, a module initially developed to quantify the formation of electroactive biofilms on stainless steels has been used to assess the corrosiveness of chlorinated seawater. Both the electrochemical potential and the cathodic current were measured on super-duplex stainless steel as a function of residual chlorine levels and seawater temperatures. In parallel, long-term localized corrosion tests have been performed in simulated environments to assess the environmental limits for the safe use of high-grade stainless steels in chlorinated seawater. It includes crevice corrosion exposure tests using adapted ISO 18070:2015 crevice formers and internal tube pitting corrosion exposure tests in model tube heat exchangers simulating heat flux from 35°C to 170°C. The synergetic effect of residual chlorine content and temperature on the risk of localized corrosion has been quantified. Corrosion resistance properties are correlated to the electrochemical monitoring data, and the environmental limits of selected base materials stainless steels have been established for duplex stainless steel UNS S32205, super-duplex stainless steel UNS S32750, hyper-duplex stainless steels UNS S32707 and UNS S33207, and the high-grade austenitic stainless steel UNS S31266.

Analysis of Groundwater Quality in Bauchi Metropolis (Nigeria) and interpretation using GIS

Fresh water resources include groundwater as a crucial component. It is essential to meeting the water needs of the country's diverse users and sectors. If the water quality is not evaluated, the usage and sustainability of the natural resources cannot be ensured. This study deals with the analysis of ground water quality in Bauchi metropolis and interpretation using ArcGIS according to the inverse distance weighting (IDW) technique. Water samples were taken from 18 hand dug wells randomly selected from six districts to assess for both bacteriological and physiochemical parameters. The bacteriological parameter tested for was Total Coliform Count, while the physiochemical parameters were: pH, Electrical Conductivity, Total Dissolves Solids, Free residual chlorine Cl-, Lead Pb, Total Hardness, Calcium Ca2+ and Magnesium Mg2+ using standard procedures prescribed by American Public Health Association, APHA. The results showed that all samples tested positive to Total Bacteria Count in the laboratory when compared to WHO Standard. whereas samples S3, S4, S5, S6, S7, S8, S12, S13, S14, S16, S17 tested negative to Total Bacteria Count under NSDWQ Standard while the remaining samples tested positive. Sample S10 was the highest at 134 cfu/100ml while S17 was the least at 1 cfu/100ml. Samples S1and S2 were not within the standard recommended pH range. Only sample S7 at 0.60 mg/L tested positive to free chlorine when compared with the NSDWQ guideline value. Sample S6 had the least TDS value of 90 mg/L while the highest value of 710 mg/L was recorded for S7. For lead content, Maximum value was recorded as 0.26 mg/L in samples S14 and S15. Sample S2 had the highest calcium value of 1.45 mg/L while S14 had the least value of 0.00 mg/L. Maximum value of magnesium was recorded in sample S14 having 3.58 mg/L while the lowest value was recorded in S11 having 0.52 mg/L. All Water samples were within the allowable limits for total hardness and are considered to be soft. It was concluded that samples S6 and S16 conformed to most of the standards while sample S7 did not conform to most of the standards when compared to WHO and NSDWQ.

Persistence kinetics of a novel disinfectant peracetic acid for swimming pool disinfection

Disinfection is essential to swimming pool water (SPW) quality. Peracetic acid (PAA) has attracted attention for water disinfection for advantages such as less formation of regulated DBPs. Persistence kinetics of disinfectants is difficult to elucidate in pools because of the complex water matrix stemming from body fluid loadings from swimmers and long residence times. In this research, the persistence kinetics of PAA was investigated in SPW benchmarked against free chlorine, use bench-scale experiments and model simulation. Kinetics models were developed to simulate the persistence of PAA and chlorine. The stability of PAA was less sensitive to swimmer loadings than chlorine. An average swimmer loading event reduced the apparent decay rate constant of PAA by 66 %, a phenomenon that diminished with increasing temperatures. L-histidine and citric acid from swimmers were identified as main retardation contributors. By contrast, a swimmer loading event instantaneously consumed 70–75 % of the residual free chlorine. The required total dose of PAA was 97 % less than chlorine under the 3-days cumulative disinfection mode. Temperature was positively correlated with disinfectant decay rate, with PAA being more sensitive than chlorine. These results shed light on the persistence kinetics of PAA and its influential factors in swimming pool settings.

Influence of residual chlorine on Ru/TiO2 active sites during CO2 methanation

Titania-supported ruthenium (Ru/TiO2) is an established catalyst for the hydrogenation of carbon dioxide to methane (Sabatier reaction). Chlorine contamination, owed to the RuCl3 precursor, is demonstrated to have a detrimental impact on methanation activity. After calcination and reduction the catalyst contains residual chlorine, shown by XPS. An aqueous ammonia wash removes Cl without leaching Ru. The washed catalysts exhibit improvements in CH4 site-time yields. Low Ru loading catalysts encounter the greatest activity enhancements after washing (∼4.5–fold). DFT calculations indicate that chlorine and CO2 directly compete for adsorption on Ru step sites, with Cl impeding the adsorption of CO2 at under-coordinated sites and at higher Cl coverages. H2-chemisorption/TPR show that Cl removal lowers the onset of low temperature H2 dissociation on Ru. DRIFTS provide evidence that the removal of Cl facilitates low temperature dissociative binding of CO2, indicated by the formation of surface bound linear CO species.

A Feasibility Study on Applying the Concept of Removing Odd Nodes to Design of Water Supply Pipe Network

Objectives : In this study, the concept of the Eulerian path, which has already been proposed as a solution to the problem of head loss and residual chlorine reduction caused by complexity of nodes and pipelines, and the non-Euerian path proposed in this study were compared and their feasibility were examined.Methods : The concepts of ‘removal of odd nodes’, ‘removal of 3-intersection nodes’, and ‘removal of zero demand nodes’ were applied to the virtual water supply networks, and the number of cases were analyzed and evaluated from the viewpoint of configuration complexity and hydraulic efficiency. For Euler graph and non-Euler graph water supply networks, each total pipe length, number of removal pipes, pressure head and flow rate were simulated with EPANET2 program.Results and Discussion : As a result of simplifying and designing new output networks for virtual Euler and non-Euler graph, it was revealed that the concept of ‘removing a 3-intersection nodes’ could be the most efficient by removing more pipes. However, in terms of configuring the output network as an Euler graph, the concept of ‘removing odd nodes’ can be considered more reasonable.Conclusion : It is difficult to configuring watersupply network as a perfect Euler graph. Therefore, the application of the concept of removing odd nodes suggested in this study can promote efficient simplification of the network. In addition, it can be thought that the application of this concept can expect efficiency in terms of hydraulics and water quality.

Combined application of EPANET and empirical model for possible formation of trihalomethanes in water distribution network of Chattogram city to identify potential carcinogenic health risk zone

The study identifies potential carcinogenic health risk-zone of Chattogram city for the occurrence of trihalomethanes (THMs) at its water distribution network. The EPANET-THMs simulation model along with an empirical model have been adopted in the study to predict THMs content of supply water of the distribution network of the city’s Karnaphuli service area. The empirical model has estimated THMs level of supply water based on influential water quality parameters, and few of these have been used as pre-set values for subsequent EPANET simulation. The simulation (R2= 0.7) shows that THMs’ concentrations throughout the network vary from 33 to 486 μg/L. Around 60% of total junctions showed THMs concentrations above 150 μg/L, while that is above 50 μg/L for most (99%) of the junctions. Residual Free chlorine, one of the precursors for the THMs formation in distribution line, has also been simulated by EPANET considering varying applied chlorine dose at the water purification unit and wall (Kw) and bulk (Kb) decay constants. The simulated free residual chlorine peaks are found to be closer to the actual values with chlorine dose of 2 mg/L, and decay constants, Kw = 1 d−1 and Kb = 1 d−1. A mean lifetime total risk of cancer due to the presence of THMs has been found to be very high. Spatial distribution of carcinogenic risk shows that the central zone of the service area is the most vulnerable zone, followed by the western and northern zone. The first ever zone wise risk identification could be used as baseline data for operational and regulatory purposes and may raise awareness among the city’s inhabitants. Furthermore, the application of EPANET in combination with an empirical model could be an effective tool for predicting THMs’ concentration in water distribution networks in developing countries like Bangladesh to minimize the expenses of measuring THMs.