Abstract
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.
Highlights
A major source of human disease is via the consumption of biologically contaminated water[1]
The antimicrobial activity of both OCl− and ECAS was significantly reduced compared to respective values under clean conditions (p < 0.0001) at all free chlorine (FC) concentrations tested
HOCl exhibited significantly greater antimicrobial activity compared to both OCl- and ECAS at 50, 100 and 150 mg L−1 FC (p < 0.01), with
Summary
A major source of human disease is via the consumption of biologically contaminated water[1]. Least developed countries (46 low-income countries confronting severe structural impediments to sustainable development) where an estimated 30% of populations, on average, have access to basic sanitation services[2] This is in contrast to upper-middle (GNI per capita $4036–$12,475) and high-income countries (GNI per capita > $12,476) which predominantly utilise centralised drinking water treatment systems to ensure the production and supply of biologically safe water[3]. The presence of residual chlorine (0.5–5 mg L−1) within redistribution networks limits microbial re-growth, helping to maintain biologically safe water at the point of delivery[3] Indicator organisms such as Escherichia coli, total coliforms, Enterococci and Clostridium perfingens[3,5], that infer the presence of faecal matter, are monitored to ensure the effectiveness of disinfection treatment processes. The use of chlorine disinfectants gives rise to the formation of disinfection byproducts [DBPs]6,7 such as trihalomethanes[8] and haloacetic acids[9]
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