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Decentralized water systems (DWS) distribute water in remote African areas. Throughout an intervention in Maniema, Congo, the influence of a DWS performing chlorination in the community's water quality was measured. Additionally, a socio-economic and WASH practices survey was conducted in the communities. Free residual chlorine (FRC) and microbiological contamination were measured; at the borehole, treatment site, distribution points, and households's water containers. In Big Five, water was collected from unimproved sources before DWS construction. Despite that, only 16,6% of households used efficient water treatment methods, resulting in 73% of water stored unsafe for consumption. After construction, household water quality drastically improved, regardless of FRC fluctuations; 93% of samples were classified as low health risk (safe). The renovation guaranteed continuous supply through electro-chlorinators in RVA, where chlorination was intermittent. Water from DWS with adequate chlorine levels prevented microbiological contamination in households for 12 hours. Although economically attractive, the system's sustainability will require future evaluation. [ABSTRACT FROM AUTHOR]

Ballast water (BW) poses the risk of introducing species. Therefore, ships install the ballast water management system (BWMS) to reduce the risks caused by BW. To gain a deeper understanding of the treatment effectiveness of the BWMS, in this study we compared the effectiveness of four different treatment processes of BWMSs on seawater phytoplankton, which were electrochlorination treatment, hydroxyl radical oxidation treatment, membrane separation and deoxygenation treatments, and UV irradiation treatment. The results showed that all four BWMSs had a reduction in phytoplankton density of over 99%. In terms of phytoplankton taxa, the effectiveness of the four BWMSs was different. The taxa removal rates of the four BWMSs were 81.25%, 39.58%, 59.31%, and 74.49%, respectively. Electrochlorination treatment and UV irradiation treatment were significantly more effective than hydroxyl radical oxidation treatment and membrane separation and deoxygenation treatments. The residual phytoplankton taxa were mainly dinoflagellate and diatoms, such as Cucumeridinium, Prorocentrum, Navicula, and Skeletonema. Taxa that can tolerate treatment may be more likely to survive and reproduce. There is still a need to continue to strengthen the development and research on the BWMS in the future to promote the development of BW management. [ABSTRACT FROM AUTHOR]

Access to clean drinking water remains a challenge in many developing countries, emphasizing the critical need for affordable, scalable and sustainable water treatment technologies. This study employs an electrochemical flow cell incorporating a 3D-printed biomimetic flow field for efficient in situ electrochlorination, avoiding water recirculation or external chloride dosing. The impact of varied ionic compositions of groundwater on electrochlorination efficiency is examined using synthetic groundwater samples, reflecting diverse hydrogeological conditions within a region in a developing country. Employing a Multilevel Factorial Design (MFD), the study highlights the significant influence of water ionic composition, flow rate, and applied current on free chlorine production. The results affirm the capability of the reactor to generate free chlorine species in a range of 0.32–6.13 mg·L−1. The specific energy consumptions oscillate between 0.49 and 19.67 Wh·mg−1 for chloride concentration in the samples ranging from 24 to 146 mg·L−1. This confirms the potential of the suggested electrochemical cell design for broad use in the studied region, and possibly in similar settings worldwide.

Ballast water (BW) poses the risk of introducing species. Therefore, ships install the ballast water management system (BWMS) to reduce the risks caused by BW. To gain a deeper understanding of the treatment effectiveness of the BWMS, in this study we compared the effectiveness of four different treatment processes of BWMSs on seawater phytoplankton, which were electrochlorination treatment, hydroxyl radical oxidation treatment, membrane separation and deoxygenation treatments, and UV irradiation treatment. The results showed that all four BWMSs had a reduction in phytoplankton density of over 99%. In terms of phytoplankton taxa, the effectiveness of the four BWMSs was different. The taxa removal rates of the four BWMSs were 81.25%, 39.58%, 59.31%, and 74.49%, respectively. Electrochlorination treatment and UV irradiation treatment were significantly more effective than hydroxyl radical oxidation treatment and membrane separation and deoxygenation treatments. The residual phytoplankton taxa were mainly dinoflagellate and diatoms, such as Cucumeridinium, Prorocentrum, Navicula, and Skeletonema. Taxa that can tolerate treatment may be more likely to survive and reproduce. There is still a need to continue to strengthen the development and research on the BWMS in the future to promote the development of BW management.

For years, gas chlorination has been the adopted disinfection technology in the treatment of Maltese potable water. Despite its strong bacterial inactivation potential, traditional chlorination generates high free chlorine residual and disinfection by-products that compromise the sensory attributes of drinking water and deter the population from consuming it. We have identified plausible alternative-to-gas-chlorination technologies for its treatment, with the aim of (a) reducing the disinfectant and/or chlorination dose used for microbial inactivation, and (b) attenuating the negative impact of putative disinfection by-products on the water's organolepsis, while safeguarding its safe-for-consumption characteristics. We have subjected ultraviolet C (UVC) irradiation, hydrodynamic cavitation (HC), ClO2 generation, and electrochlorination (NaClO) to bacteriological and physicochemical bench-scale studies to assess their bacterial inactivation efficacy and by-product generation propensity, respectively. All the tested technologies except HC achieved a minimum of 3 Log10 microbial inactivation, with NaClO and ClO2 appearing more effective over neutral and alkaline pH conditions, respectively. In addition, we have identified synergistic effects of cavitation on UVC for Enterococcus faecalis inactivation, stemming from enhancement in oxidative stress. Moderate reductions in the total dissolved solid content and Ca2+ hardness of the tested water also emerged following prolonged cavitation. For feasibility studies, the performance of the technologies was further evaluated on the following areas: (a) implementation, (b) practicality, (c) adaptability, (d) integration, (e) environment and sustainability, and (f) cost and effect. Electrochemical generation of NaClO emerged as the most promising technology for further on-site work, followed by ClO2 and UVC. [ABSTRACT FROM AUTHOR]

When obtaining sulfuric acid from pyrite concentrates, a significant amount of waste is generated in the form of pyrite cinders that require disposal. The methods used in processing this raw material are, as a rule, the pyrometallurgical processes of chlorination and chloride sublimation, the disadvantages of which include increased energy consumption and a lack of complexity in the extraction of valuable components. Hydrometallurgical processes are in less demand due to their multi-stage nature and complexity of execution. The method of chemical activation developed at the JSC "Institute of Metallurgy and Ore Beneficiation" makes it possible to isolate iron and non-ferrous metals into separate, middling products and to concentrate noble metals in the cake at the first stage. Physical and chemical studies of the cake found that its basis comprises iron compounds. The silver in the cake is associated with pyrite, while the gold is associated with hematite; it is also possible to find gold in the form of AuCl3. The content of gold in the cake is 1.5 g/t, and the silver content is 17.7 g/t. Based on physical and chemical studies and data from the literature, various versions of the hydrochlorination method are proposed to open the cake. [ABSTRACT FROM AUTHOR]

The number of desalination plants worldwide increased exponentially in the last decade. This is basically a consequence of fast population growth combined with the expansion of water scarcity zones, even though desalination processes are, comparatively, much more energy intensive than other freshwater membrane treatment processes. SeaWater Reverse Osmosis (SWRO) has gained preference among the most used desalination processes due to its compacity, flexibility and energetic efficiency. However, desalination processes produce a concentrated brine that needs to be disposed of and represents an environmental challenge to be tackled. Currently in the literature, the most explored solutions for brine treatment are based on the extraction of valuable resources from the concentrate, also called brine valorization. Late discussions have pointed out that other approaches such as reuse for energy production and disinfection products might also be a solution for the same challenge. This review presented the current state of the art of SWRO brine valorization including the following methods: disinfectant (chlorine) production and salinity gradient energy generation; expanding the possibilities for brine treatment and reuse. [Display omitted] • Disinfectant and energy production can be a solution for SWRO brine valorization. • SWRO brine valorization technologies are still at low technology readiness levels. • Nanofiltration is a promising pretreatment for brine mining and chlorine production. • A SWOT analysis of SWRO brine valorization solutions is presented. • To stimulate brine valorization, specific legislation is needed. [ABSTRACT FROM AUTHOR]

• Electrochemical treatment effectively addresses complex dye mixtures in water. • Photoelectro-Fenton meets effluent color disposal standards. • Significant Chemical Oxygen Demand reduction achieved with photoelectron-Fenton. • Enhanced performance observed in industrial effluent, aided by active chlorine for additional removal. Many industries use complex synthetic organic dye mixtures in their dyeing processes, producing wastewater effluents with complex dye mixtures. In this study, electrochemical advanced oxidation processes like electrochemical oxidation (ECO), ECO with electrogenerated H 2 O 2 (ECO-H 2 O 2), electro-Fenton (EF), and photo electro-Fenton (PEF) with UVC irradiation were compared to discolor and mineralize a mixture of Methyl Orange, Methyl Red, and Toluidine Blue O with a boron-doped diamond anode and a gas-diffusion cathode. While ECO and ECO-H 2 O 2 required long times to achieve a complete discoloration, the dyes were quickly degraded by EF and PEF due to the oxidation with ∙OH formed from Fenton's reaction. Almost complete mineralization was rapidly achieved by PEF for a solution with 424 mg O 2 L−1 of chemical oxygen demand (COD) at a current density of 66.6 mA cm−2 due to the synergistic action of the UVC irradiation. Additionally, the treated effluent was evaluated using the DFZ (Deutsche Farb Zah) parameter for water condition, offering a new perspective and distinguishing this work from previous studies focused on electrified technologies for dye removal. The same behavior has been found for the mixture of such dyes in an industrial effluent upon PEF treatment, even showing faster discoloration and COD reduction as result of the additional removal with active chlorine formed from Cl− oxidation. Ion-exclusion HPLC analysis of the treated synthetic effluent revealed the formation of final carboxylic acids like malic, acetic, oxalic, and formic. Released nitrate, ammonia, and nitrite were detected as nitrogenated by-products from the initial N of the dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnéli Ti 4 O 7 electrodes with morphologies of TF, NP, NR, NW were fabricated. • Electroporation was induced by the locally enhanced electric field over NW tips. • Electrochlorination was promoted by the locally enriched Cl- ions over NW tips. • Electroporation and electrochlorination had synergistic effects on cell inactivation. • Ti 4 O 7 -NW anodes enabled rapid and efficient inactivation of various G+/G- bacteria. Waterborne pathogens in drinking water remains a prominent cause of morbidity and mortality in developing rural areas. Electrochlorination offers a promising alternative for decentralized water disinfection, but its efficiency was strongly restrained by the low Cl- concentrations in natural waters. Herein, we proposed a Magnéli Ti 4 O 7 nanowire-assisted electrochemical approach via forming locally enhanced electric field over nanowire tips for reinforcing electroporation, and via forming locally enhanced charge density for promoting Cl- enrichment and subsequent electrochlorination on anodic nanowire tips. Ti 4 O 7 nanowires induced the enhancement of electric field by 4 orders of magnitude and Cl- concentration by ∼3 orders of magnitude at nanowire tips, and promoted ∼3 times more active chlorine generation at a voltage of 3.0 V compared with non-nanostructured one. Synergistic electroporation and electrochlorination on nanowires enabled rapid and efficient disinfection with hydraulic retention time of ∼36 s and energy consumption below ∼5 J/L/log for inactivation of various gram-positive/negative bacteria and phage MS2. Analyses of cell morphology and membrane integrity revealed that electroporation-induced cell pores provided diffusion channels of reactive chlorine species for oxidative damage of cell structures, resulting in ∼1.5–4.5 times lower energy consumption than the thin-film, nanoparticle, and nanorod ones. The excellent operation stability for tap water with significant bacterial inactivation and active chlorine generation demonstrated its great application potential for decentralized water disinfection. [ABSTRACT FROM AUTHOR]

Recently, the electrochemical treatment of wastewater polluted by recalcitrant organics and containing chlorides was shown to be significantly improved adopting proper operative conditions such as suitable anodes and cathodes and low current density. In particular, the use of suitable cathodes such as carbon felt or silver could increase the removal of TOC and reduce the formation of chlorinated by‐products. In this study, attention was focused on the utilization of carbon felt cathodes with the main aim to evaluate the effect of air pressure on the process using phenol as model organic pollutant. It was shown that, in the presence of carbon felt cathode, the use of pressurized air allows both to increase the removal of TOC and to reduce the formation of chlorate. Moreover, the effect of the nature of the anode and of the presence of FeSO4, in order to study the involvement of electro‐Fenton process, was evaluated. [ABSTRACT FROM AUTHOR]

As chlorate concentrations have been found to be harmful to human and animal health, governments are increasingly demanding strict control of the chlorate concentration in drinking water. Since there are no chlorate sensors available, the current solution is sampling and laboratory analysis. This is costly and time consuming. The aim of this work was to investigate Sensor Data Fusion (SDF) as an alternative approach, with a focus on chlorate formation in the electrochlorination process, and design an observer for the real-time estimation of chlorate. The pH, temperature and UV-a absorption were measured in real time. A reduced-order nonlinear model was derived, and it was found to be detectable. An Extended Kalman Filter (EKF), based on this model, was then used to estimate the chlorate formation. The EKF algorithm was verified experimentally and was found to be capable of accurately estimating chlorate concentrations in real time. Electrochlorination is an emerging and efficient method of disinfecting drinking water. Soft sensing of chlorate concentrations, as proposed in this paper, may help to better control and manage the process of electrochlorination. [ABSTRACT FROM AUTHOR]

For years, gas chlorination has been the adopted disinfection technology in the treatment of Maltese potable water. Despite its strong bacterial inactivation potential, traditional chlorination generates high free chlorine residual and disinfection by-products that compromise the sensory attributes of drinking water and deter the population from consuming it. We have identified plausible alternative-to-gas-chlorination technologies for its treatment, with the aim of (a) reducing the disinfectant and/or chlorination dose used for microbial inactivation, and (b) attenuating the negative impact of putative disinfection by-products on the water’s organolepsis, while safeguarding its safe-for-consumption characteristics. We have subjected ultraviolet C (UVC) irradiation, hydrodynamic cavitation (HC), ClO2 generation, and electrochlorination (NaClO) to bacteriological and physicochemical bench-scale studies to assess their bacterial inactivation efficacy and by-product generation propensity, respectively. All the tested technologies except HC achieved a minimum of 3 Log10 microbial inactivation, with NaClO and ClO2 appearing more effective over neutral and alkaline pH conditions, respectively. In addition, we have identified synergistic effects of cavitation on UVC for Enterococcus faecalis inactivation, stemming from enhancement in oxidative stress. Moderate reductions in the total dissolved solid content and Ca2+ hardness of the tested water also emerged following prolonged cavitation. For feasibility studies, the performance of the technologies was further evaluated on the following areas: (a) implementation, (b) practicality, (c) adaptability, (d) integration, (e) environment and sustainability, and (f) cost and effect. Electrochemical generation of NaClO emerged as the most promising technology for further on-site work, followed by ClO2 and UVC.

When obtaining sulfuric acid from pyrite concentrates, a significant amount of waste is generated in the form of pyrite cinders that require disposal. The methods used in processing this raw material are, as a rule, the pyrometallurgical processes of chlorination and chloride sublimation, the disadvantages of which include increased energy consumption and a lack of complexity in the extraction of valuable components. Hydrometallurgical processes are in less demand due to their multi-stage nature and complexity of execution. The method of chemical activation developed at the JSC “Institute of Metallurgy and Ore Beneficiation” makes it possible to isolate iron and non-ferrous metals into separate, middling products and to concentrate noble metals in the cake at the first stage. Physical and chemical studies of the cake found that its basis comprises iron compounds. The silver in the cake is associated with pyrite, while the gold is associated with hematite; it is also possible to find gold in the form of AuCl3. The content of gold in the cake is 1.5 g/t, and the silver content is 17.7 g/t. Based on physical and chemical studies and data from the literature, various versions of the hydrochlorination method are proposed to open the cake.

Bacteriological contamination in drinking water is known to be responsible for the spread of various waterborne diseases. Although chlorine is frequently used as disinfectant in water treatment, low-cost disinfecting technologies in the villages of developing and under-developed countries are not yet successfully implemented. This study contributed in designing a simple and inexpensive water disinfection unit to produce chlorine from the naturally available dissolved chloride of groundwater by electrochlorination, using inert and cheap graphite electrodes. Laboratory-based experiments were performed in both batch and continuous flow reactors to study the effect of time, current, electro charge loading (ECL), and surface area of electrodes in chlorine generation and bacterial inactivation. Controlled experiments in continuous mode in the absence of chlorine further indicated the possibility of partial inactivation of bacteria under the influence of the electric field. Finally, a treatment unit with drilled anodes, and undrilled cathode electrodes, in continuous flow set-up was installed in four schools of four different villages in West Bengal, India. An average residual chlorine concentration and removal efficiency of total coliform in the designed systems were determined as 0.3 ± 0.07 mg/L, and 98.4% ± 1.6%, respectively. [ABSTRACT FROM AUTHOR]

• Electrochlorination outperformed chlorination under realistic conditions. • Acidic pH at anode surface might enhance inactivation of E. coli and MS2 during electrochlorination. • Chloride-based radicals might enhance disinfection. • Reactive oxygen species did not impact on disinfection in a single pass. Electrochlorination has gained research interest for its potential application as decentralized water treatment. A number of studies have displayed promising efficiency for water disinfection. However, a comprehensive comparison of in situ electrodisinfection to existing disinfection techniques, particularly under realistic water composition and flow rates, still needs additional research efforts. The aim of this study is to evaluate in situ electrochlorination while comparing the treatment with conventional chemical chlorination for point-of-entry decentralized disinfection at the household level. An electrochemical flow cell reactor was operated in a single pass mode considering water flow and water consumption for a household of four family members. Disinfection efficiency assessment of both electrochemical and chemical chlorination was conducted using bacterial and viral surrogates, E. coli and MS2 bacteriophage. Furthermore, a techno-economic analysis was conducted, using the levelized cost of water, to compare two electrochemical chlorination scenarios (i.e., electrical grid energy use, and solar panel powered system) and benchmarked against the baseline treatment of chemical chlorination. The findings revealed increased inactivation efficiency of in situ electrochlorination over conventional chlorination (p -value < 0.05). The synergetic impact of radicals and chlorine, and/or contribution of high chlorine concentration at acidic pH near anode surface were identified as key factors that could enhance disinfection performance of in situ electrochlorination. The techno-economic analysis demonstrated that electrochemical treatment, when operated using renewable energy sources, is not only a more environmentally sustainable approach, but also emerges as a more economically feasible solution for decentralized water treatment application. The results highlight that in situ electrochlorination is a more advanced alternative to decentralized water chlorination. However, further fundamental research on products and by-products formation under various water matrices is required. [Display omitted] [ABSTRACT FROM AUTHOR]

• Electrochlorination achieved efficient conversion of phosphonate to ortho-p and elimination. • Free HEDP was released from Fe-HEDP complex throught LMCT for subsequent degradation. • Conversion of Cl− to HClO and FeIVO2+ via Electro-Fenton-like treatment achieved beneficial utilization of matrix waste. • Pivotal reactive species of phosphonate degradation by electrochlorination were HClO, FeIVO2+, and 1O 2. Phosphonate used as scale inhibitor is a non-negligible eutrophic contaminant in corresponding polluted waters. Besides, its conversion to orthophosphate (ortho-P) is a precondition for realizing bioavailable phosphorus recovery. Due to the feeble degradation efficiency with less than 30 % from classical Fenton commonly used in industrial wastewater treatment and itself vulnerable to strong inhibition interference of matrix chloride ions, we proposed an electrochemical approach to transform the native salt in the solution into oxidizing substances, sort of achieving beneficial utilization of matrix waste, and enhanced the ortho-P conversion rate of 1-Hydroxyethane-1,1-diphosphonic acid (HEDP) to 89.2 % (± 3.6 %). In electrochlorination system, it was found that HEDP rapidly complexed with Fe(II) and then coordinated in-situ Fe(III) to release free HEDP via intramolecular metal-ligand electron transfer reaction. The subsequent degradation mainly rooted in the oxidation of pivotal reactive species HClO, FeIVO2+ and 1O 2 , causing C-P and C C bonds to fracture in sequence. Eventually the organically bound phosphorus of HEDP was recovered as ortho-P. This study acquainted the audiences with the rare mechanism of chloridion-triggered HEDP degradation under electrochemical way, as well as offered a feasible technology for synchronous transformation of organically bound phosphorus to ortho-P and elimination from phosphonates. [Display omitted] [ABSTRACT FROM AUTHOR]

This study deals with the implementations of electrochemical technology for the on-site production of sodium hypochlorite (NaOCl) and hydrogen from seawater for utilization in the steam power plant. The effects of electrical current and seawater temperature on the performance of electrochlorination system are investigated. The obtained results show that current efficiency increases with increasing electrical current. The current efficiency of the system is calculated as 94% at a maximum electric current with a value of 4000 A and maximum temperature with a value of 30 °C. Electricity consumption increases for the unit generation of available chlorine in the case of both enhancements of electrical current and seawater. Hydrogen generation is directly proportional to the variation of the electrical current. Also, improvement in seawater temperature provides more efficient hydrogen generation. Moreover, energy and exergy efficiencies of the whole system are positively affected by an increase of current. However, energy and exergy efficiencies are determined to be 50.4% and 3.04%, respectively, under the best operational conditions. Besides, the cheapest product cost of the hydrogen gas is calculated as $4.04/kg under the greatest electrical current and seawater temperatures. Image 1 • This study concerns with on-site generation of sodium hypochlorite and hydrogen. • System is highly essential to control biofouling for effective plant operation. • The effects of electrical current and seawater temperature are investigated. • Hydrogen cost and amount of generation are defined by means of analysis. [ABSTRACT FROM AUTHOR]

• A new electrolysis-based hybrid system for recycling nutrient medium was analyzed. • Electrolytically-disinfected nutrient medium increased biomass productivity. • We used the membrane filtration (MF)-electrolysis-ultraviolet (UV) system. • MF-electrolysis-UV system achieved 99.5 % disinfection and 80.3 % carbon removal. • The system achieved nutrient medium recycling, with >50 % cost reduction. Recycling and reusing of nutrient media in microalgal cultivation are important strategies to reduce water consumption and nutrient costs. However, these approaches have limitations, e.g., a decrease in biomass production, (because as reused media can inhibit biomass growth). To address these limitations, we applied a novel membrane filtration‒electrolysis‒ultraviolet hybrid water treatment method capable of laboratory-to-large-scale operation to increase biomass productivity and enable nutrient medium disinfection and recycling. In laboratory-scale experiments, electrolysis effectively remove the biological contaminants from the spent nutrient medium, resulting in a high on-site removal efficiency of dissolved organic carbon (DOC; 80.3 ± 5 %) and disinfection (99.5 ± 0.2 %). Compared to the results for the recycling of nutrient medium without water treatment, electrolysis resulted in a 1.5-fold increase in biomass production, which was attributable to the removal of biological inhibitors from electrochemically produced oxidants (mainly OCl−). In scaled-up applications, the hybrid system improved the quality of the recycled nutrient medium, with 85 ± 2 % turbidity removal, 75 ± 3 % DOC removal, and 99.5 ± 2 % disinfection efficiency, which was beneficial for biomass growth by removing biological inhibitors. After applying the hybrid water treatment method, we achieved a Spirulina biomass production of 0.47 ± 0.03 g L−1, similar to that obtained using a fresh medium (0.53 ± 0.02 g L−1). The on-site disinfection process described herein is practical and offers a cost-saving and environmental friendly alternative for nutrient medium recycling and reusing water in mass and sustainable cultivation of microalgae. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation has been demonstrated to be a useful method for removing biorefractory organic pollutants in mature landfill leachate but suffers from low efficiency in eliminating ammonium because of its resistance to being oxidized by HO • or free chlorine (FC) at decreased pH. Here, we propose a new bipolar membrane-electrochlorination (BPM-EC) process to address this issue. We found that the BPM-EC system was significantly superior to both the undivided and divided reactors with monopolar membranes in terms of elevated rate of ammonium removal, attenuated generation of byproducts (e.g., nitrate and chloramines), increased Faradaic efficiency, and decreased energy consumption. Mechanistic studies revealed that the integration of BPM was helpful in creating alkaline environments in the vicinity of the anode, which facilitated production of surface-bound HO • and FC and eventually promoted in situ generation of ClO • , a crucial reactive species mainly responsible for accelerating ammonium oxidation and selective transformation to nitrogen. The efficacy of BPM-EC in treating landfill leachates with different ammonium concentrations was verified under batch and continuous-flow conditions. A kinetic model that incorporates the key parameters was developed, which can successfully predict the optimal number of BPM-EC reactors (e.g., 2 and 5 for leachates containing 589.4 ± 5.5 and 1258.1 ± 9.6 mg L -1 NH 4 + -N, respectively) necessary for complete removal of ammonium. These findings reveal that the BPM-EC process shows promise in treating ammonium-containing wastewater, with advantages that include effectiveness, adaptability, and flexibility.

Ubiquitous presence of chloride in water effluents may result in the unavoidable electrogeneration of active chlorine species when considering the application of electrochemical advanced oxidation processes as water treatment technologies. However, less attention has been drawn to the subsequent generation of other combined chlorine species such as chloramines. In this work, the electrogeneration of chloramines has been assessed in different water matrices containing NHCl 4 , urea or synthetic urine. The yield of chloramines has been followed in-situ by differential electrochemistry mass spectroscopy (DEMS) during electrochemical advanced oxidation process with boron-doped diamond (BDD) anodes. Furthermore, the influence of several variables such as chloride concentration, pH or organics concentration on the different distribution of inorganic monochloramine, dichloramine and trichloramine released as products has been considered. Image 1 • Chloramines followed on-line by differential electrochemical mass spectroscopy. • Inorganic chloramines formed from electrochemical oxidation of urea and urine. • Higher chloride content enhances chlorine evolution and chloramines yield. • Higher O 2 evolution at alkaline pH competitively decreases chloramines formation. • Scavenging effects of competing ionic species in the matrices diminishes chloramines. [ABSTRACT FROM AUTHOR]

A large variety of Advanced Oxidation Processes (AOPs) to degrade trace organic compounds during water treatment have been studied on a lab scale in the past. This paper presents the combination of inline electrolytic chlorine generation (ECl2) with low pressure UV reactors (UV/ECl2) in order to allow the operation of a chlorine-based AOP without the need for any chlorine dosing. Lab studies showed that from a Free Available Chlorine (FAC) concentration range between 1 and 18 mg/L produced by ECl2 up to 84% can be photolyzed to form, among others, hydroxyl radicals (OH) with an UV energy input of 0.48 kWh/m3. This ratio could be increased to 97% by doubling the UV energy input to 0.96 kWh/m3 and was constant throughout the tested FAC range. Also the achieved radical yield of 64% did not change along the given FAC concentration range and no dependence between pH 6 and pH 8 could be found, largely simplifying the operation of a pilot scale system in drinking water treatment. Whereas with ECl2 alone only 5% of benzotriazoles could be degraded, the combination with UV improved the degradation to 89%. Similar results were achieved for 4-methylbenzotriazole, 5-methylbenzotriazole and iomeprol. Oxipurinol and gabapentin were readily degraded by ECl2 alone. The trihalomethanes values were maintained below the Germany drinking water standard of 50 µg/L, provided residual chlorine concentrations are kept within the permissible limits. The here presented treatment approach is promising for decentralized treatment application but requires further optimization in order to reduce its energy requirements.

The most common disinfectants for water treatment are based on chlorine and its compounds. Practically, water treatments with chlorine compounds have no alternative, since they provide, in comparison to other effective processes such as ozonization or ultraviolet irradiation, high residual disinfection capacity. Unfortunately, all of chlorine-based compounds for disinfection tend to degrade during storage, thus reducing the concentration of active chlorine. Apart from degradation, additional problems are transportation, storage and handling of such hazardous compounds. Nowadays, a lot of attention is paid to the development of electrochemical devices for in situ production of chlorine dioxide or sodium hypochlorite as efficient disinfectants for water treatment. The most important part of such a device is the electrochemical reactor. Electrochemical reactor uses external source of direct current in order to produce disinfectants in electrochemical reactions occurring at the electrodes. Construction of an electrochemical device for water treatment is based on evaluation of optimal conditions for electrochemical reactions during continues production of disinfectants. The aim of this study was to develop a low-cost electrochemical device for the production of disinfectant, active chlorine, at the place of its usage, based on newly developed technical solutions and newest commercial components. The projected electrochemical device was constructed and mounted, and its operation was investigated. Investigations involved both functionality of individual components and device in general. The major goal of these investigations was to achieve maximal efficiency in extreme condition of elevated room temperature and humidity with a novel device construction involving coaxial heat exchanger at the solution inlet. Room operation of the proposed device was investigated when relative humidity was set to 90% and the ambient temperature of 38°C. The obtained results in such extreme operation conditions reveled that it was possible to obtain required concentration of 0.85% of active chlorine with maximal temperature of outlet electrolyte of 35.3°C, which is within the limits of optimal temperatures. [Projekat Ministarstva nauke Republike Srbije, br. 172046]

Chloride oxidation is a key industrial electrochemical process in chlorine-based chemical production and water treatment. Over the past few decades, dimensionally stable anodes (DSAs) consisting of RuO 2 - and IrO 2 -based mixed-metal oxides have been successfully commercialized in the electrochemical chloride oxidation industry. For a sustainable supply of anode materials, considerable efforts both from the scientific and industrial aspects for developing earth-abundant-metal-based electrocatalysts have been made. This review first describes the history of commercial DSA fabrication and strategies to improve their efficiency and stability. Important features related to the electrocatalytic performance for chloride oxidation and reaction mechanism are then summarized. From the perspective of sustainability, recent progress in the design and fabrication of noble-metal-free anode materials, as well as methods for evaluating the industrialization of novel electrocatalysts, are highlighted. Finally, future directions for developing highly efficient and stable electrocatalysts for industrial chloride oxidation are proposed., (© 2023 Wiley-VCH GmbH.)

Chlorination is one of the most widely used disinfection and water treatment technologies. Electrochlorination has proved to be one of the most reliable applications of electrochemistry in water treatment with improved performance in comparison to conventional chlorination. Several research efforts have been devoted to the development of these technologies; however these studies barely considered the release of chlorine volatile species (Cl 2 , ClO 2 and Cl 2 O). Here, a semi-quantitative analysis of various volatile species produced during the electrolysis of highly saline water (0.6 M NaCl) at BDD electrode has been conducted by differential electrochemical mass spectrometry (DEMS) using the dual thin layer flow through cell. The effect of solution pH and electrolyte flow rates on the release of volatile species has been considered. Electrolysis of 0.6 M NaClO 4 evidenced the competition between O 2 and Cl 2 evolution towards the electrogenerated OH radicals during electrolysis in presence of chloride. Evolution of Cl 2 was favored at acidic pH, whereas its evolution is inhibited at alkaline pH. The quantification of released species highlighted that the evolution of chlorine corresponds to a ca. 80% of the current efficiency, which is a significant contribution to the overall electrochlorination process. [ABSTRACT FROM AUTHOR]

The management of ship ballast water is essential to stemming the introduction of non-indigenous species. Approval for onboard installation of a system to treat ballast water requires rigorous land-based testing as dictated in the G8 guideline by the International Maritime Organization. However, this testing lacks standardization—most notably augmentation of organic carbon for influent water by adding chemical additives. Electrochlorination is a popular treatment method for ballast water, in which chlorinated oxidants react with organisms and organic matter in water. The additives could thus affect the treatment efficacy of the ballast water. Here, we examined the effects of several candidates of organic carbon additives on the consumption of total residual oxidant (TRO), the production of disinfection byproducts (DBPs), plankton survival, and ecotoxicity. The TRO consumption over five days of storage was higher in electrochlorinated seawater amended with lignin and Metamucil when compared with seawaters with other organic carbon compounds. DBP production varied by almost two orders of magnitude as a function of the various additives. This was largely attributed to the production of tribromomethane and dibromoacetic acid. The survival of Artemia franciscana was significantly different across waters of different organic carbon additives. Algal toxicity testing with the marine haptophyte Isochrysis galbana significantly reduced growth in lignin- and Metamucil-treated seawaters, but not with other organic carbon compounds. Bioluminescence in Vibrio fischeri sharply declined in electrochlorinated seawaters with all types of organic carbon compounds, but no toxicity was manifested once the electrochlorinated seawaters were neutralized with sodium thiosulfate. The varying degrees of outcome suggest that it might be better to eliminate the requirements of adding organic carbon to test water as long as natural water was used for land-based testing of BWMS. If needed, the additives could be used in proportion to the composition of the organic matter in water being tested. [ABSTRACT FROM AUTHOR]

Cyanide is widely present in electroplating wastewater or metallurgical effluents. In the present study, the electrochemical destruction of cyanide with various anode and cathode compositions under alkaline conditions was investigated. The results indicated that the electrochemical system using RuO 2 /Ti as anode and activated carbon fiber (ACF) as cathode in the presence of sodium chloride was efficient for the cyanide removal. In this system, in situ generation of HClO by anodic oxidation of Cl − at RuO 2 /Ti anode occurred with the H 2 O 2 generation by O 2 reduction at ACF cathode. As confirmed by the electron spin resonance technique, the reaction between HClO and H 2 O 2 led to the generation of singlet oxygen, which was responsible for the cyanide removal. Further experiment indicated that the cyanide removal efficiency increased with the increase of the current density or the sodium chloride concentration. Cyanate was identified as main product in the system. Besides, the system exhibited good stability for the cyanide removal, which was beneficial to its practical application. [ABSTRACT FROM AUTHOR]

The performance of Cu-EDTA decomplexation and copper recovery by photo-assisted electrolysis (UPE) process using TiO 2 /Ti as anode and stainless-steel as cathode was explored by adding H 2 O 2 /Cl − . The Cu-EDTA decomplexation and Cu recovery were well fitted with a pseudo-first-order reaction model. The results indicated that with the addition of H 2 O 2 into the UPE process (H 2 O 2 -UPE process), the kinetic constant of Cu-EDTA decomplexation was increased from 0.0677 min −1 to 0.0880 min −1 , and the kinetic constant of Cu recovery was increased from 0.0607 min −1 to 0.0749 min −1 . Similar enhancement was observed by adding Cl − into the UPE process (EC-UPE process), where the kinetic constant of Cu-EDTA decomplexation was increased from 0.0272 min −1 to 0.0632 min −1 . Correspondingly, the kinetic constant of Cu recovery was increased from 0.0249 min −1 to 0.0565 min −1 . In the H 2 O 2 -UPE process, the efficiency of Cu-EDTA decomplexation and Cu recovery was optimal at the initial solution pH of 2.5–3.5; in the EC-UPE process, an optimum current density of 1.00 mA/cm 2 was obtained. Intermediates were detected in H 2 O 2 -UPE process and a decomplexation pathway was proposed. A different degradation pathway was concluded in the EC-UPE process. [ABSTRACT FROM AUTHOR]

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The spread of aquatic invasive species through ballast water is a major ecological and economical threat. Because of this, the International Maritime Organization (IMO) set limits to the concentrations of organisms allowed in ballast water. To meet these limits, ballast water treatment systems (BWTSs) were developed. The main techniques used for ballast water treatment are ultraviolet (UV) radiation and electrochlorination (EC). In this study, phytoplankton regrowth after treatment was followed for six BWTSs. Natural plankton communities were treated and incubated for 20 days. Growth, photosystem II efficiency and species composition were followed. The three UV systems all showed similar patterns of decrease in phytoplankton concentrations followed by regrowth. The two EC and the chlorine dioxide systems showed comparable results. However, UV- and chlorine-based treatment systems showed significantly different responses. Overall, all BWTSs reduced phytoplankton concentrations to below the IMO limits, which represents a reduced risk of aquatic invasions through ballast water. [ABSTRACT FROM PUBLISHER]

We examined the synergistic effects of CO 2 injection on electro-chlorination in disinfection of plankton and bacteria in simulated ballast water. Chlorination was performed at dosages of 4 and 6 ppm with and without CO 2 injection on electro-chlorination. Testing was performed in both seawater and brackish water quality as defined by IMO G8 guidelines. CO 2 injection notably decreased from the control the number of Artemia franciscana , a brine shrimp, surviving during a 5-day post-treatment incubation (1.8 and 2.3 log 10 reduction in seawater and brackish water, respectively at 6 ppm TRO + CO 2 ) compared with water electro-chlorinated only (1.2 and 1.3 log 10 reduction in seawater and brackish water, respectively at 6 ppm TRO). The phytoplankton Tetraselmis suecica , was completely disinfected with no live cell found at >4 ppm TRO with and without CO 2 addition. The effects of CO 2 addition on heterotrophic bacterial growth was not different from electro-chlorination only. Total residual oxidant concentration (TRO) more rapidly declined in electro-chlorination of both marine and brackish waters compared to chlorine + CO 2 treated waters, with significantly higher amount of TRO being left in waters treated with the CO 2 addition. Total concentration of trihalomethanes (THMs) and haloacetic acids (HAAs) measured at day 0 in brackish water test were found to be 2- to 3-fold higher in 6 ppm TRO + CO 2 -treated water than in 6 ppm TRO treated water. The addition of CO 2 to electro-chlorination may improve the efficiency of this sterilizing treatment of ballast water, yet the increased production of some disinfection byproducts needs further study. [ABSTRACT FROM AUTHOR]