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UNESCO-IHE Institute for Water Education, Delft (2015)

Assessment of solar photoreactor for disinfection of drinking water with focus on bacterial inactivation

Oradei D.

Titre : Assessment of solar photoreactor for disinfection of drinking water with focus on bacterial inactivation

Auteur : Oradei D.

Etablissement de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2015

Résumé
SODIS is the well known solar disinfection process that has been used for treating drinking water at household level in developing countries for the last decades. The method is effective, simple and affordable, however the traditional way of utilizing commercial plastic bottles filled with water (<30 NTU) exposed for at least s ix hours to direct sunlight comes with limitations ; one of these being the limited volume of water that can be treated per batch. In this research a new low-cost solar recirculated batch reactor with a volume of 100 L, NOVO75, was assessed according to the harmonized testing protocol to evaluate household water treatment technologies (WHO, 2014) ; the focus was on bacterial inactivation and, specifically, Escherichia coli K12 was the target of the study. The research examined the disinfection of water at different flow rates to evaluate the lethal dose of UVA required to achieve "protective" (2 log removal) or "highly protective" disinfection level (4 log removal) of E.coli K12 using two water matrices (saline and challenge water). It was found that when saline water (distilled water + 0.9%NaCl) was used the highest inactivation values were given at lower flow rates (5 or 10L/min) ; on average the UVA dose required to achieve "highly protective disinfection" was 200 kJ/m2. While 6 log was achieved with UVA doses ranging from 375-516 kJ/m2. The negative effect of the flow rate was perceived less when using challenge water (high in turbidity and organic content) ; the water’s complex characteristics allowed only for inactivation that averaged around 3.6 log. To achieve the "protective disinfection" level in challenge water a UVA dose ranging between 230 -320 kJ/m2was required. When treating challenge water, 4 log were rarely inactivated with a dose of 505kJ/m2circa. To conclude the assessment, the performance of the reactor was compared to that of recirculated reactor (70-100 L) and a batch reactor (20 L). Results have shown that the NOVO75 performs more efficiently than the other two systems, in terms of solar energy required to treat one litre of water. Upon completing the evaluation based on WHO’s guidelines, the NOVO75 has been proven to be a reliable household water treatment technology. Furtherm ore, its results, even when using challenge water (100 NTU), fall well within the WHO’s expected baseline performance of 3 log removal (WHO, 2011).

Sujets  : drinking water treatment ; disinfection ; Water quality ; bacteria ; batch reactors

Présentation

Page publiée le 30 décembre 2016, mise à jour le 18 octobre 2018