(156c) Disinfection of Water By Adsorption Combined With Electrochemical Treatment

The process of adsorption using graphite based adsorbents with electrochemical regeneration was developed at the University of Manchester for the removal of low concentrations of organic impurities from water. The technology employs a graphite intercalation compound (GIC) adsorbent that can be electrochemically regenerated. This process has significant potential application for water recycling since it does not involve the addition of chemicals and no solid or liquid wastes are generated. Safe storage of water for recycling often requires that the water is disinfected. To date there have been no studies of the effect of the adsorption / electrochemical regeneration process on any microorganisms present in the water. The aim of the present work was to investigate the removal and disinfection of microorganisms by adsorption on a GIC adsorbent followed by electrochemical treatment. The adsorption of an enteropathogenic bacterium, Escherichia coli, was performed using GIC particles followed by electrochemical treatment under a range of experimental conditions in an air agitated sequential batch reactor. The adsorption of E. coli cells on the GIC adsorbent was found to be a fast process and was capable of removing >99% E. coli cells from solution after 10 min with a ca. 6.5log₁₀ reduction in the CFU concentration. The electrochemical treatment gave 100% regeneration efficiency showing that the capacity of the GIC adsorbent did not diminish over five adsorption and regeneration cycles . An ~8-log₁₀ reduction of E. coli was achieved on each cycle. During electrochemical regeneration significant indirect electrochemical disinfection of E. coli present in the supernatant solution was observed. The process of adsorption using GIC adsorbents with electrochemical regeneration is capable of disinfecting a high concentration of E. coli at low current density and low energy consumption. The most likely mechanisms for electrochemical disinfection include electrochlorination, direct electrochemical attack and pH effects.  In the absence of chloride, both the adsorption of E. coli on the GIC and the electrochemical regeneration were found to be less effective for water disinfection. In spite of this, effective disinfection was achieved in the absence of chloride by the appropriate selection of operating conditions. This observation indiates that the process of disinfection by adsorption with electrochemical regeneration could be employed for disinfection without the formation of chlorinated disinfection by–products.