Monitoring of methylene blue monomers and dimers to control the bacterialogical water quality including application to p
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RESEARCH ARTICLE
Monitoring of methylene blue monomers and dimers to control the bacterialogical water quality including application to photocatalysis Myriam Ben Said 1 & Latifa Bousselmi 1 & Ahmed Ghrabi 1 Received: 6 April 2020 / Accepted: 18 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, we propose the development of a rapid and reliable method to control and to monitor microbial water quality. The methylene blue (MB) decolorization assay was based on the analysis of spectral profiles of dye in interaction with a different bacterial concentration. The determination of dye decolorization rate (DDR) shows a correlation between the MB reduction rate and the bacterial density. Moreover, the kinetic of the monomer and dimer equilibrium of MB in water mainly, the monitoring of bounded MB species in relationship with a knowed concentration of target bacteria, was allowed to establish a relationship between MB decolorization rate and bacterial density. Furthermore, this method was applied to evaluate the water quality after photocatalysis. Based on this method, the photocatalytic effects on bacterial density was highlighted by the decrease in DDR after photocatalytic treatment with fractioned times (0 to 5 h); this increase was followed by a decrease of bounded MB species and, an increase in free MB forms miming the reduction of bacterial density due to the biocide effects of photocatalysis process. However, the analysis of spectra profiles shows a weak but a continuous decrease in bounded MB dimer and monomer forms in the treated water samples exempt of culturable bacteria. Moreover, the MB spectra profiles were tended toward a negative control spectrum without superposition. Thus, the possibility of the presence of viable but non-culturable bacteria was expected; therefore, to optimize this tertiary water treatment process, an extending on proceeding time was recommended to avoid the bacterial resuscitation after photocatalysis. Keywords Water . Methylene blue . Bacteria . Dye decolorization rate
Introduction After water disinfection, the detection of bacterial viability is considered a primordial stage to control and to improve the efficiency of the water treatment process. Indeed, the dysfunction of the tertiary water treatment phase can contribute to the spread of water-borne diseases and consequently, may have harmful effects on the public health and the environment. Generally, a culture-based method is used for water assessment. However, these conventional methods are timeResponsible Editor: Sami Rtimi * Myriam Ben Said [email protected] 1
Wastewater and Environment Laboratory, Center of Researches and Water Technologies of Borj-Cedria (CERTE) Tourist Route of Soliman, Nabeul, PO-Box No. 273, 8020 Soliman, Tunisia
consuming and labour-intensive. Indeed, the confirmed results often require several days of analysis and for enumeration may only detect a small proportion of the total population (Cangelosi and Meschke 2014; Chen et al. 2011; Sartory and Watk
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