The interaction of silver ions and hydrogen peroxide in the inactivation of E. coli: a preliminary evaluation of a new long acting residual drinking water disinfectant

Abstract

The inactivation efficiencies of silver ions, hydrogen peroxide and their combination was studied as part of a performance evaluation of the combined disinfectant for drinking water applications. The major advantages of such combined disinfectant include, low toxicity of its components, long lasting residual effect and low disinfection by product formation. Specific strains of E. coli (E. coli-B (SR-9) and E. coli K-12) were used in this study as target microorganisms and the separate and combined inactivation efficiencies of silver and hydrogen peroxide were evaluated at different concentrations and exposure durations. Both, silver and hydrogen peroxide exhibited a significant inactivation performance even at concentrations that do not pose any health risk according to the EEC, WHO and the USEPA (the USEPA Maximum Contaminant Level (MCL) of silver is 90 ppb, and currently, there is no MCL for hydrogen peroxide but it is approved as a food additive in the USA). Combinations of 1:1000 silver:hydrogen peroxide (w) exhibited higher inactivation performance as compared with each of the disinfectants alone and in some cases a synergistic effect was observed, i.e., the combined disinfectant exhibited higher inactivation performance than the sum of the inactivation levels of the separate disinfectants. Thus, for example, one hour exposure to 30 ppb silver, 30 ppm hydrogen peroxide and their combination yielded 2.87, 0.65 and 5 logs of inactivation respectively. While the rate of inactivation shown by this combined disinfectant, now available commercially in a stabilized formulation is relatively slow, it may well hold promise as a secondary disinfectant providing long lasting residuals and biofilm control required for distribution systems. Its disinfection action may be similar to chloramines, the use of which has been recently outlawed in France and in Germany and which are now under careful scrutiny in other countries due to the formation of undesirable by-products.

Efficient disinfection of Escherichia coli in water by silver loaded alumina

“…Furthermore, the high bactericidal activity in neutral condition suggested that this catalyst is a very potential material to apply in drinking water disinfection. Ag + ions do elute from the catalyst surface, but the amount is no more than 0.09 mg/L in 1 h, and the World Health Organization (WHO) declared that silver does not cause adverse health effects and set a secondary maximum concentration level (MCL) of 90 lg/L [19,27,36]. Therefore, silver loaded on alumina was thought not only to increase the effectiveness of this catalyst system but also to be safe and economical, since the catalyst could be used several times after regeneration.…”

A Concept in Bactericidal Materials: The Entrapment of Chlorhexidine within Silver

“…Thus, exposure to silver ions damages multiple components of bacterial cell metabolism, including the permeability of the cell membrane, which leads to gross cellular structural changes, blockage of transport processes, and interference in the activity of vital enzymatic systems such as the respiratory cytochromes, alteration of proteins, and binding to DNA and RNA, which in turn affects their functionality. [6,17] Whereas combinations of cationic silver with other biocides such as silver sulfadiazine with or without chlorhexidine digluconate, [23] copper, [24] and hydrogen peroxide [25] are well known and used, [9,11] the use of metallic silver in biocidal combinations has been limited to the coating or impregnating of biocidal polymers with silver [26] or to the mixing of antibiotics with silver. [27] All of these combinations displayed synergistic activity.…”

Влияние Коллоидного Раствора Наночастиц Серебра На Микробиоценоз Пищеварительного Тракта Цыплят-Бройлеров

“…4). Полученные нами результаты согласовываются с данными зарубежных и отечественных исследователей (Shahverdy, 2007, Pedahzur, 1995, которые отмечают, что серебро стимулирует иммунитет, стабилизирует обмен веществ в организме и обезвреживает бактерии, вирусы и грибки, оставаясь относительно толерантным к симбиотической микрофлоре (Hidaka, 2005). Благодаря новейшим технологиям эти свойства серебра могут быть многократно усиленны за счет особенностей влияния наночастиц на различные биологические объекты (Roberfroid et al 1995).…”