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Articles by S. Watkins
Total Records ( 2 ) for S. Watkins
  P. Maharjan , T. Clark , M. Frank , B.B. Martins , M.K. Foy and S. Watkins
  Four commercially available hydrogen peroxide products were tested for residuals and efficacy over time. Each product was added at the rate of 59.14, 118.28 and 177.42 ml per 3780 ml of water creating stock solutions. Test solutions that actually mimic the bird drinking rate were made from each stock solution mixing at the rate of 29.57 ml of stock solution added to 3780 ml of water. Residual activities of test solutions prepared were measured from day 0 to day 5. Forty-eight hours post treatment, a 5 ml aliquot of water with a heavy microbial load was introduced into the test solutions as challenge and microbial plating for aerobic bacteria and mold was done for zero and one hour contact times. Results of this experiment suggest that an Effective Residual Concentration (ERC) of 25-50 ppm of hydrogen peroxide in test solution starts at 59. 14 ml of stock solution prepared for all products evaluated. Stabilized products stay at the higher residual level and can maintain ERC for a longer time than non-stabilized products. Significant bacterial reductions (p<0.05) within an hour of contact time was achieved at the lowest concentration tested, 59.14 ml of stock solution made, for all products provided that the ERC was maintained. Higher residuals or longer contact time were required for mold control.
  P. Maharjan , S. Cox , T. Clark and S. Watkins
  A bench top experiment was conducted to test three commercially available water sanitizing products for residuals and efficacy over time. Product A uses modified ambient oxygen to create hydroxyl ions in water and works based on an Advanced Oxidation Process (AOP). Product B is 50% stabilized hydrogen peroxide and Product C is 5.25% sodium hypochlorite. Two trials were conducted. Test solutions for Product A were made by infusing gas at 0.33 Liters Per Minute (LPM) diffusing into 1 liter of suboptimal water (microbial load >4.47 log10 cfu/ml; Chlorine (Cl) residual = 0 ppm). Stock solutions were first prepared for Product B and C. Stock solution for Product B was prepared at two different doses, 2 and 4 ml of the product, mixed with 128 ml of deionized water (Cl = 0 ppm) separately whereas for Product C, the stock was created mixing 4 ml of the product with 128 ml of deionized water. Test solutions for Product B and C that actually mimic the bird drinking rate were then made from each stock solution mixing at the rate of 1 ml of stock solution added to 128 ml of suboptimal water for a volume of 1L of suboptimal water. Water samples were taken for test solutions over a period of 24 h post treatment and plated for aerobic bacteria (APC) and mold counts. Residual levels for all the products were taken into account at each water sampling occasion. Results indicated that the AOP method can be used as an alternative water sanitation measure over the chemical methods.
 
 
 
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