Analogies and differences between photocatalytic oxidation of chemicals and photocatalytic inactivation of microorganisms

Journal of Photochemistry and Photobiology A: Chemistry

Escalas-Cañellas

et al. 2014

a b s t r a c tA 4-factor, multilevel, full factorial design of 240 experiments was performed in order to investigate the effect of temperature on the inactivation efficiency of spiked Escherichia coli in simulated solar disinfection of a synthetic secondary effluent. The initial population of the microorganisms was 10 3 , 10 4 , 10 5 and 10 6 CFU/mL, the exposure time 1, 2, 3 and 4 h, the treatment temperature 20, 30, 40, 50 and 60• C and the sunlight intensity 0, 800 and 1200 W/m 2 . Radical changes in bacterial behavior, process efficiency and remaining populations were observed, while treating effluents in discreet temperatures. Elevating treatment temperature from 20 to 40• C drastically impaired disinfection. Thermal inactivation with no regrowth predominated at 50• C and total inactivation of microorganisms was observed at 60• C in nonirradiated samples. Irradiation at 800 and 1200 W/m 2 much increased inactivation efficiency, especially at 50 and 60• C, proving sensitive light-temperature synergy at those temperatures. Total inactivation was achieved within 4 h under a range of treatment conditions, including all samples at 1200 W/m 2 , or 60• C samples at 800 W/m 2 . Also, 99.9-100% efficiencies and final population below 1000 CFU/100 mL were obtained at 800 W/m 2 and temperatures of 50 • C and above. Treatment time, temperature and intensity are the critical parameters for the disinfection process, while initial population is insignificant for removal efficiency. An explanation of the mechanism of the process as well as a general linear model predicting the outcome of the experiments is also suggested.

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Section: Introductionmentioning

confidence: 99%

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

Journal of Photochemistry and Photobiology A: Chemistry

Escalas-Cañellas

et al. 2014

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“…Wastewater was recirculated around the nonilluminated, non-sonicated experimental set-up and the corresponding graphs describe the changes when H 2 O 2 and iron were added to the solution. We notice the increase of the population, when no reactants were added, due to the existence of nutrients and salts that favor bacterial growth in this water matrix [35]. H 2 O 2 is a substance with disinfecting action, while iron itself is not toxic for bacteria.…”

Section: Results Of the Step-wise Construction Of The Joint Treatmentmentioning

confidence: 88%

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

Papoutsakis

Ultrasonics Sonochemistry

et al. 2015

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.

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“…Here, a fluctuation is visible, reducing with increasing intensity. Literature suggests that this phenomenon is attributed to the simultaneous disinfecting action of light and (i) photo-activation of previously non-cultivable bacteria [25], (ii) an initial adaptation phase for bacterial population in the new dilution medium, with possible acclimatization shocks (which induce decay) and (iii) the growth of bacteria which is supported by this medium [20,35]; the presence of nutrients and ions enhances bacterial growth, and bacteria which have not been lethally damaged by the action of light undergo repair and are also able to reproduce and compensate for the lost numbers.…”

Section: Resultsmentioning

confidence: 99%

“…The change in the water matrix to wastewater, is however rather unexplored. Marugan et al [20] have stated the modification of disinfection potentials when the chemistry of the matrix is altered and Salih [21] marked the importance of consideration of pollution load. Furthermore, Sichel et al [22] and Rincon and Pulgarin [23] discussed the idea of minimum dose for inactivation and the importance of irradiation conditions on photolysis and Malato et al [24] in their review mentioned the importance of light dispersion.…”

Section: Introductionmentioning

confidence: 99%

Solar disinfection modeling and post-irradiation response of Escherichia coli in wastewater

Chemical Engineering Journal

Escalas-Cañellas

et al. 2015