Thesis Archive
Storage Stability and Disinfection Performance on Escherichia Coli of Electrolyzed Seawater (2016-2017)
Regina G. Damalerio
Abstract:
-Electrolysis of seawater has been employed as a disinfectant due to its capability to produce residual oxidants that are vital for water disinfection. While several studies focused on its disinfection performance, its storage performance as a disinfectant in terms of its physicochemical properties and bactericidal efficiency through time has yet to be investigated. Two batches of electrolysis of 2750-mL seawater were conducted at the selected current of 1.5 A and electrolysis time of 20 minutes. One hundred (100)-mL of electrolyzed seawater samples were transferred to each amber glass and opaque plastic bottles, and the bottles were stored in a dark place at ambient temperature. Disinfection performance on E. coli and physicochemical properties such as pH, oxidation-reduction potential (ORP), and free chlorine concentration were evaluated on the 0th, 2nd, 5th, 9th, 14th, 20th, 23rd, 28th, and 30th storage days. Results showed that pH increased while ORP and free chlorine decreased through time. The changes may be attributed to the change in the distribution of hypochlorous acid and hypochlorite through time since the formation of these species is a function of pH. Furthermore, the dissociation of hypochlorous acid to hypochlorite was further supported by the single stage decomposition of electrolyzed seawater in both amber and opaque plastic bottles. Free chlorine in amber glass and opaque plastic bottles was observed to follow first-order decay with KD constants -0.046 day-1 and -0.066 day-1, respectively. Hypochlorous acid as the predominant component throughout the experimentation may also be the reason for the no observable growth of Escherichia coli. Further investigation was done on the 2nd and 3rd week after day-28 bottles were momentarily opened. Results showed that ESW is still capable as a disinfectant due to no observable growth of E. coli despite showing an increase in pH, and decrease in ORP and free chlorine concentration.
Adviser:
Dr. Arnel B. Beltran
Dr. Aileen H. Orbecido