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Application of a Novel Silver‐Stabilized Hydrogen Peroxide in Secondary Disinfection of Potable
Water and Proposed Mechanism for and Enhanced Antibacterial Activity
Nancy Martin1, Paul Bass2 and Steven N. Liss2,3*1Department of Biomedical and Molecular Sciences, 2School of
Environmental Studies, and 3Department of Chemical Engineering, Queen’s University, Kingston, Ontario Canada K7L 3N6
Acknowledgements
Queen’s University, Kingston, CanadaDr. Nancy Martin, Paul Bass, Jerry Liu, and Dr. Mahendran BasuvarajRyerson, Toronto, CanadaDr. Martini KroukampUniversity of Stellenbosch, Stellenbosch, South AfricaDr. Gideon Wolfaardt
Engage Grant
FedDev Applied Research & Commercialization Program
Financial Support and Supply of Materials
“Cost of Doing Nothing”
• Kathy Caldwell, President of the American Society of Civil Engineers (ASCE), Science 334, 21 October 2011 p 289
• 2009 Report Card for America’s Infrastructure –Grade of “D”
• 26.5 billion litres of clean drinking water lost per day
Fundamentals• Three types of change processes in a socio‐technical system
(Geels and Kemp (2007) Technology in Society 29, 441‐455)
– Reproduction (e.g. new pipe materials)– Transformation (e.g. climate change adaptation; microbiological issues, emerging health issues and contaminants)
– Transition (major shift; drawing water from a well to distribution systems)
• Rygaard , M., et al. Designing water supplies: Optimizing drinking water composition for maximum economic benefit, Water Research (2011), 45, 3712‐3722
Disinfection Properties of Hydrogen Peroxide & Silver
• Tote, K. , et al. 2009. Evaluation of hydrogen peroxide‐based disinfectants in a new resazurin microplatemethod for rapid efficacy testing of biocides. Journal of Applied Microbiology 107: 606–615
• Batterman, S. A., et al. 2001. Evaluation of the Efficacy of a New Secondary Disinfectant Formulation Using Hydrogen Peroxide and Silver and the Formulation of Disinfection By‐Products Resulting From Interactions with Conventional Disinfectants, Final Report, EPA Project 825362 (University of Michigan & Hebrew University)
• Armon R, et al. 2000. Controlling biofilm formation by hydrogen peroxide and silver combined disinfectant. Water Science & Technology 42(1‐2):187‐192.
• Pedahzur R, et al. 2000.The efficacy of long‐lasting residual drinking water disinfectants based on hydrogen peroxide and silver. Water Science & Technology 42(1‐2):293‐298.
Key Findings• Ability to reduce chlorination
disinfection by‐products• Met water quality requirements • Suppressed microbial activity
within water distribution lines• Stability under heating
conditions similar to those found within domestic hot water heaters.
A pilot‐scale study conducted in the town of Killaloe, Ontario to evaluate the performance of the AVIVE™ Water Treatment Solution, using Huwa‐San Peroxide (HSP) as an alternative to chlorine‐based disinfection methods.
Objectives
• Compare the efficacy of HuwaSan, lab grade hydrogen peroxide (HP) and sodium hypochlorite (NaOCl) for suspended cultures of indicator bacteria.
• Establish contact times (CT) that achieved effective control to determine HSP’s potential utility in disinfection.
• Distinguish the effect of silver and peroxide in HSP on metabolic activity of a P.aeruginosa PAO1 biofilm.
TSB – Tryptic soy broth; LB‐ Luria Bertani; SYN – synthetic wastewater media; HP– hydrogen peroxide; NaOCl – sodium hypochlorite
Antibacterial Activity
Contact Time and Proposed Mechanism of Action
1 HP – hydrogen peroxide; 2 NaOCl – sodium hypochlorite; ND – not determined; presence (+) or absence (‐) of catalase.
Contact Time and the Effect of Cations
As the biofilm grows within CO2permeable tubing, CO2 is released as a metabolic byproduct. A secondary, non‐CO2 permeable tubing traps the CO2 in the “annular space” until the sweeper gas (CO2 free air) delivers the CO2 to the CO2 analyzers for measurement.
CO2 Evolution Measurement System
0
5
10
15
0.00 10.00 20.00 30.00 40.00 50.00 60.00
CO2 ( u
M / Hou
r)
Time (Hours)
70 ppm
CO2 increase with no subsequent decrease CO2 increase followed by decrease
02468
101214
0.00 20.00 40.00 60.00 80.00 100.00
Time (Hours)
140 ppm
CO2 decrease only
02468101214
0 20 40 60 80 100 120 140
Time (Hours)
500 ppm
Typical Metabolic Response Curves to HuwaSan
Inhibition by Silver and Peroxide
The average % reduction in a Pseudomonas PAO1 biofilm’s CO2production rates when exposed to 0 ‐500 ppm HSP and solutions of HSP‐silver and silver nitrate at corresponding silver concentrations of 0 ‐ 375 ppb. After a steady respiration rate was achieved (20 hours) the films were exposed to the HSP or silver solutions for 2 hours.
Effluent Counts and Live:Dead Ratio
Key Findings •At pH 7, HSP and hypochlorite were equally effective; HSP was superior at pH 8.5.
•Overall HSP was found to be more effective than HP owing to stabilization and the residual effect associated with silver peroxide.
•Once HSP is associated with the bacterial cell surface it is less susceptible to inactivation by catalase.
•Electrostatic interactions between HSP and the bacterial cell increases the efficiency of killing over that seen with HP. Interactions between HSP and the cell surface are inhibited in the presence of cations. Silver serves as a mechanism of action for HSP, but is not the primary disinfectant.
•Silver alone, at concentrations equivalent to that found in HSP (0 – 375 ppb) has a negligible affect on the metabolic activity of a biofilm; the activity of peroxide in HSP is the primary mechanism leading to cell inactivation and death.
Future Work
• Microbial ecology of water distribution systems
• Continued work on mechanism(s) of action
• Application specific validation studies