Chlorine solutions are used extensively for the production of biologically safe drinking water. The capability of point-of-use [POU] drinking water treatment systems has gained interest in locations where centralised treatment systems and distribution networks are not practical. This study investigated the antimicrobial and anti-biofilm activity of three chlorine-based disinfectants (hypochlorite ions [OCl-], hypochlorous acid [HOCl] and electrochemically activated solutions [ECAS]) for use in POU drinking water applications. The relative antimicrobial activity was compared within bactericidal suspension assays (BS EN 1040 and BS EN 1276) using Escherichia coli. The anti-biofilm activity was compared utilising established sessile Pseudomonas aeruginosa within a Centre for Disease Control [CDC] biofilm reactor. HOCl exhibited the greatest antimicrobial activity against planktonic E. coli at >50 mg L−1 free chlorine, in the presence of organic loading (bovine serum albumen). However, ECAS exhibited significantly greater anti-biofilm activity compared to OCl- and HOCl against P. aeruginosa biofilms at ≥50 mg L−1 free chlorine. Based on this evidence disinfectants where HOCl is the dominant chlorine species (HOCl and ECAS) would be appropriate alternative chlorine-based disinfectants for POU drinking water applications.

Point-of-use (POU) drinking water treatment systems provide solutions for communities where centralized facilities are unavailable. Effective POU systems treat and reduce the number of pathogens in POU water supplies often employing disinfection. Chlorine disinfection results in the formation of disinfection by-products (DBPs), such as trihalomethanes (THMs), through the reaction of chlorine with natural organic matter (NOM) over time. Although THMs are known to be harmful to human health, little is known about their production within POU systems. This study compares the disinfectants; Electrochemically Activated Solutions (ECAS), hypochlorous acid (HOCl), and sodium hypochlorite (NaOCl), with respect to their potential to produce THMs within POU drinking water systems. Headspace solid-phase microextraction (HS-SPME) gas chromatography mass spectrometry (GC-MS) was utilized to quantify THMs in treated water samples containing NOM (Suwannee River humic acid, 4 mg L −1). All disinfection treatments were matched to free chlorine concentrations of 1, 3, and 5 mg L −1 , using reaction times of 1, 5, and 10 min. THMs were produced at free chlorine concentrations of 5 mg L −1 and at reaction times of 5 and 10 min for all disinfectants. ECAS or HOCl, resulted in the formation of significantly lower total THM concentrations across all reaction times and free chlorine concentrations, compared to NaOCl. ECAS can be generated at the POU requiring only water, salt and energy for production, and this study demonstrates that its use results in reduced formation of THMs, compared with NaOCl. Further work is required to replicate these findings within scaled-up POU water treatment systems.

10Approximately 800 million people live without clean drinking water. Diarrhoea is responsible 11 for between 1.7 and 2 million deaths each year (primarily children) which are the result of 12 poor drinking water quality and sanitation. The main aim of this study was to demonstrate 13 the production of drinking water from a raw water source using an off-grid drinking water 14 production system. The off-grid drinking water production system (DWPS) developed at 15 UWE Bristol, combines an ultra-filtration (UF) system with in situ generation of 16 electrochemically activated solutions (ECAS). ECAS has two functional roles within the 17 system; to manage biofilms within the UF system and as a disinfectant. Integrated in-situ 18 probes (pH, oxidation reduction potential, chlorine, conductivity and dissolved oxygen) 19 coupled with a water quality sensing network (pH, water temperature, conductivity and 20 dissolved oxygen) enabled real time monitoring of; the operational efficiency of the DWPS, 21 and the physicochemical parameters of both the raw water source and the produced drinking 22water. Spot samples of both raw and treated water were sent for independent chemical and 23 microbial analysis at an accredited laboratory which demonstrated that the DWPS produced 24 biologically safe potable drinking water according to the Drinking Water Inspectorate (DWI) 25 standards. Samples from the raw water source were shown to be consistently unsuitable for 26 human consumption, failing several of the DWI standards for potable water supply, including 27 coliform bacteria. This study demonstrated that the novel off-grid DWPS was capable of 28 producing DWI standard drinking water from a heavily biologically contaminated water 29 source. 30 Keywords 31Off-grid; drinking water production; electrochemically activated solutions; ultrafiltration. 32

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