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Title: An evaluation of alternative technologies for drinking water disinfection
Author: Kerwick, Mark Ian
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2004
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A methodology has been developed and used to evaluate the alternatives to chlorination for primary and residual drinking water disinfection. From the evaluation process it was concluded that at present none of the altemalives could viably replace chlorination for both primary and residual disinfection. The study did however highlight the potential of electrochemical disinfection technologies to provide primary and residual disinfection in the future by the generation of a range of oxidants including chlorine species. Hence, three electrochemical technologies (a mixed oxidant generator, a direct electrolyser with carbon aerogel electrodes, and a direct electrolyser called Zappi ™ )were chosen to assess their potential as an alternative to conventional chlorination for primary and residual disinfection. The disinfection efficiencies of the three devices were assessed. Anolyte produced from the mixed oxidant generator was compared directly with hypochlorite at equal doses. Anolyte was shown be more effective against E. coli, reducing the E. coli count by >6 logs and to have the same potential for trihalomethane formation in slow sand filtered water, generating 30).μg/L when dosed at lmg/L for 24 hours. The carbon aerogel and Zappi™ direct electrolysers were shown to disinfect E. coli in a range of electrolytes and water matrices. Total measurable E. coli log reductions were achieved in both devices using a chloride electrolyte. Significantly, both devices were effective against E. coli in sulphate electrolytes without the generation of chlorine, with 3 and 4 log reductions respectively. The carbon aerogel device was also shown to be effective in a good quality sewage effluent matrix and tap water reducing E. coli by >4 logs. Whilst, the Zappi was shown to reduce E. coli by >2 logs in slow sand filtered water. Phosphate was shown to significantly reduce disinfection in both direct devices. The effectiveness of the direct electrolysers was shown to be variable against other micro-organisms. The Zappi™ device was effective against the virus, bacteriophage MS2 in a sulphate electrolyte, with a >5 log inactivation after 30 minutes. Whilst, the carbon aerogel device achieved a > 1 Jog reduction of Enterovirus after 40 minutes in tap water and a 2 log reduction of Cryptosporidium oocysts in tap water. It should be noted that the reduction in Cryplosporidium could be attributable to removal via filtering rather than inactivation by oxidant attack. Possible mechanisms for electrochemical disinfection were investigated of these oxidant generation was shown t~ be responsible for disinfection_ Determination of the oxidant species generated proved to be problematic. The presence of chlorine and the high voltages used in all three devices made it difficult to isolate specific oxidants. The bactericidal properties of two poly-viologens were assessed 10 determine their potential for mediating oxidant generation for drinking water disinfection. The poly-viologens were shown to reduce the E. coli count by 6 logs. However, the results were inconclusive due to the variability between poly-viologen batches. These studies do however infer that poly-viologens may still have a future use as oxidant mediators in disinfection devices.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available