Electrochemical Activation

1. Comparison of Bacteriocidal Efficacy of Electrochemically Activated Solutions with that of Commercially Available Hypochlorite Allison Helme, Mariam Ismail, Dr. Chen-Lu Yang, and Dr. Frank Scarano ATMC, Biomedical Engineering - Biotechnology, and Medical Laboratory Science Departments, University of Massachusetts Dartmouth Abstract Electrochemical Reactor Activation Minimum Bacteriocidal Concentration The reactor consists of an acrylic chamber containing two Ruthenium oxide coated titanium electrodes. A zirconium oxide diaphragm (approximate pore size 5-10 microns) separates the two electrodes. The diaphragm allows passage of ions but is largely impermeable to water. Voltage is applied to the reactor using a DC power supply. A 0.5% NaCl solution (5g/L) was activated at 20V for 30 minutes. The anolyte and catholyte solutions were analyzed for hypochlorite concentration and pH. A second activation was performed using the same parameters without the zirconium oxide diaphragm in place. In this case only one solution was produced. Clear tubes are plated on additional growth media to verify sterility. The lowest concentration of the solution that produces a sterile medium is referred to as the minimum bacteriocidal concentration, or MBC. This is used as a measure of the antimicrobial effectiveness of each solution. A lower MBC signifies a more effective solution. Electrochemical activation (ECA) has been recently developed as a quick and efficient method of hypochlorite production, and many claim increased efficacy when compared to conventional disinfectant solutions. Many potential applications, including hospital disinfection, wastewater treatment, routine drinking water disinfection, and biological decontamination have been suggested. Three solutions were produced by electrochemical activation of 0.5% NaCl and compared to commercially available NaOCl. The NaOCl concentration and pH of each solution was measured, and the MBC of each was determined using seven common microbial pathogens. All solutions were effective, but the ECA solution was 100% effective against all seven pathogens at approximately 1/3 the necessary concentration of NaOCl. The ECA anolyte solution produced was of neutral pH and still 100% effective at approximately 1/4 the necessary NaOCl concentration. This process may lead to production of a highly effective yet non-caustic disinfectant that would have countless scientific, medical, military, and public health applications. MBC Results Hypochlorite / pH All solutions tested were more effective than commercially available hypochlorite, especially the anolyte solution, which showed an overall MBC of 0.0033%. This is particularly remarkable due to its relatively neutral pH. Hypochlorite Titration Commercially available solutions of sodium hypochlorite (household bleach) are often used as disinfectants. They contain 6.00% NaOCl as per the label, but repeated iodometric titration confirms the concentration is only 2.33%. Electrochemical activation of water involves the exposure of water and added salts to an electrical potential difference. When NaCl is the added salt, the primary product will be hypochlorite. The complex reactions that occur within the electrochemical reactor produce a meta-stable solution containing several reactive ions and free radicals, including ozone, hydrogen peroxide, chlorine, hypochlorite, hydrochloric acid, and hydroxide ions. The primary method of hypochlorite production is as follows: 2 Cl- ↔ Cl2+ 2e- Cl2 (aq) + H2O ↔ HClO + Cl- + H+ HClO ↔ ClO- + H + Conclusion Antimicrobial Efficacy Electrochemical Activation Each solution is added to an equal volume of a general purpose bacterial growth medium for a 5-tube serial dilution. 100 μL of a 0.5 McFarland bacterial suspension is added to each tube. After 24 hours’ incubation at 35˚C, cloudiness in the media is indicative of positive growth. The successful production of a neutral yet highly effective antimicrobial agent has recently gained national attention due to its numerous potential applications. This study serves to confirm the claims of increased antimicrobial effectiveness seen with these solutions. Areas of further study include anti-viral and anti-parasitic studies, as well as shelf-life, composition, and biocompatibility analyses. Spectrophotometric Analysis • Organisms tested: • Escherichia coli (ATCC 35218) • Staphylococcus aureus (ATCC 25923) • Pseudomonas aeruginosa (ATCC 27853) • Bacillus cereus (ATCC 11778) • Candida albicans (ATCC 10231) • Enterococcus faecalis (ATCC 51299) • Klebsiella oxytoca (ATCC 49131) References Feng, C and K Suzuki et al. Water disinfection by electrochemical treatment. Biores. Tech. Vol 94, Iss 1, pp. 21-25, Aug 2004. Ismail, M and CL Yang. Disinfection of water and industrial effluents by electrochemical activation. Sigma Xi Scientific Research Society Exhibition, Apr 2006. Jeong, J and JY Kim et al. Inactivation of Escherichia coli in the electrochemical disinfection process using a Pt anode. Chmsphr Vol 67, Iss 4, pp. 652-659, Mar 2007. Li, XY and HF Diao et al. Electrochemical wastewater disinfection: Identification of its principal germicidal actions. J. Envir. Engrg., Vol 130, Iss 10, pp. 1217-1221, Oct 2004. Li, XY and F Ding et al. Electrochemical disinfection of saline wastewater effluent. J. Envir. Engrg., Vol 128, Iss 8, pp. 697-704, Aug 2002. Schneider, RF. Iodometric Titration – Lab Exercise. Chemistry Professor - Stony Brook University. www.sinc.sunysb.edu/class/che133/lectures/cal036.html A series of measurements, taken at various known concentrations, were used to establish a standard curve by linear regression. This regression was used to determine the hypochlorite concentrations of generated solutions. (Abs = -1.12 + 138.75 * concentration R-square = 0.99) Wavelength scans were performed at different concentrations to determine the ideal wavelength for hypochlorite measurement. The wavelength used for this study was 292.5 nm. This example shows apparent growth of E. coli in tubes 4 and 5 (cloudiness). Tubes 1, 2, and 3 remain clear.