The antagonistic and synergistic effects of temperature during solar disinfection of synthetic secondary effluent

Gamo

Chemical Engineering Journal

et al. 2014

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In this study, simulated solar disinfection of secondary effluent was followed by dark storage at different temperatures or different receiving water matrices. E. coli illumination was followed by 3-day monitoring of the bacterial population and its adaptation in different temperature conditions in the dark. The subsequent survival was linked to the dose received during exposure to light, and results were obtained on the environmentally induced prolongation of survival, maintenance of population or excessive growth, at 4, 20 and 37˚C, respectively. An additional set of experiments at 20˚C was subjected to dilution in E. coli-free synthetic wastewater, water from Lake Leman, (synthetic) seawater and Mili-Q water. Post-irradiation NOTICE: this is the author's version of a work that was accepted for publication in Chemical Engineering Journal. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Chemical Engineering Journal [Vol. 253, p. 366-376, October 2014]. DOI: 10.1016DOI: 10. /j.cej.2014 2 monitoring was also conducted, studying 50%, 10% and 1% dilution rates, and the results were attributed to the two parameters of dilution medium and dilution ratio. However, different responses were found based on the acquired dose during pre-treatment. This indicates the importance of the illumination prior to storage, and the preference of bacteria in some matrices over the others. Survival was linked to initial population, dose, dilution and medium; shorter illumination times are to be considered according to the receiving water matrix.

Section: Resultsmentioning

confidence: 82%

“…The chemicals were used as received. A 10% dilution of the said wastewater was inoculated with E. coli, to form a suspension containing 10 6 CFU/mL and bear organic carbon values closer to the desired ones [61].…”

Section: Methodsmentioning

confidence: 99%

Monitoring the post-irradiation E. coli survival patterns in environmental water matrices: Implications in handling solar disinfected wastewater

Gamo

Chemical Engineering Journal

et al. 2014

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“…An extensive analysis of the disinfection kinetics and the regrowth potential of the photo-treated secondary effluent was published before by the authors (Giannakis et al, 2014a;2014b). In summary, reverse results were observed for the process efficiency, when the DOE was analyzed;…”

Section: Challenging Reciprocity Law In Temperature-controlled Disinfmentioning

confidence: 95%

“…An hourly-drawn sample was kept in sterile plastic flasks in the dark, at room temperature (~25˚C), for post-irradiation measurements of survival/regrowth after 24 and 48 h. Experiments were performed twice, while sampling (and afterwards, plating) was done in duplicates, from 2-3 consequent dilutions. (Giannakis et al 2014a). Finally, the runs with null intensity were not used in dose calculations, as they reflect no dose impact and act as blank thermal treatment experiments.…”

Section: Experimental Details: Light Source Bacterial Enumeration Anmentioning

confidence: 99%

Temperature-dependent change of light dose effects on E. coli inactivation during simulated solar treatment of secondary effluent

Chemical Engineering Science

Escalas-Cañellas

et al. 2015

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In this study, simulation of solar disinfection of secondary effluents was performed, to assess the dose effects, as instructed by the reciprocity law. A full factorial experimental design on the operational parameters of the process was performed (time, temperature, bacterial load, light intensity) and three response variables were estimated (disinfection efficiency, regrowth after 24, and 48 hours). In the 240 disinfection experiments, an erratic behavior was observed in all responses to light exposure, attributed to the combination of both irradiation intensity and temperature during treatment. As a result, the validity of the reciprocity law between light dose and irradiation intensity is challenged. The majority of the cases failed to comply with it, indicating the dependence on temperature conditions, as well as the applied intensity. Dose affected the bacterial regrowth potential after 24 and 48 h in a more conventional way. It appears that in order to attain a valid projection of the outcome of solar disinfection in secondary effluent, intensity and dose are not the only parameters to be considered, with temperature also having to be taken under consideration.

“…On the one hand, this behavior (Fig. 5a) is attributed to the reduced kinetics of the photo-Fenton reaction: it is known that temperature increases chemical reactions' kinetics, plus OrtegaGomez et al [61] revealed the reduced inactivation rate in another bacterial species but also mesophilic with similar optimal growth temperature with E. coli, according to the Arrhenius equation and on the other hand, treating wastewater at temperatures close to the optimal growth conditions, can delay bacterial inactivation [62].…”

Section: Environmental Influencementioning

confidence: 95%

Ultrasound enhancement of near-neutral photo-Fenton for effective E. coli inactivation in wastewater

Papoutsakis

Ultrasonics Sonochemistry

et al. 2015

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a b s t r a c tIn this study, we attempt for the first time to couple sonication and photo-Fenton for bacterial inactivation of secondary treated effluent. Synthetic wastewater was subjected to sequential high-frequency/low power sonication, followed by mild photo-Fenton treatment, under a solar simulator. It was followed by the assessment of the contribution of each component of the process (Fenton, US, hv) towards the removal rate and the long-term survival; sunlight greatly improved the treatment efficiency, with the coupled process being the only one to yield total inactivation within the 4-h period of treatment. The short-term beneficial disinfecting action of US and its detrimental effect on bacterial survival in long term, as well as the impact of light addition were also revealed. Finally, an investigation on the operational parameters of the process was performed, to investigate possible improvement and/or limitations of the coupled treatment; 3 levels of each parameter involved (hydraulic, environmental, US and Fenton) were tested. Only H 2 O 2 increased improved the process significantly, but the action mode of the joint process indicated potential cost-effective solutions towards the implementation of this method.