Combining solar irradiation with chlorination enhances the photochemical decomposition of microcystin-LR.
Water Res
; 159: 324-332, 2019 Aug 01.
Article
en En
| MEDLINE
| ID: mdl-31103737
ABSTRACT
Microcystin-LR (MC-LR) generated by cyanobacteria is a potent toxin threatening human health. In this study the kinetics and mechanisms of MC-LR elimination from drinking water under solar irradiation with free chlorine (the solar/chlorine process) was evaluated. The rate of MC-LR degradation was dramatically enhanced in the solar/chlorine process (1.1â¯×â¯10-2 s-1) compared with chlorination alone (2.6â¯×â¯10-3 s-1) or solar irradiation alone (1.2â¯×â¯10-4 s-1) with a free chlorine dose of 42⯵M (3.0â¯mgâ¯L-1 as Cl2). The enhancement was due to the presence of hydroxyl radicals, reactive chlorine species (RCS), and ozone during free chlorine photolysis. The second-order rate constants of Cl ⢠and Cl2â¢- reacting with MC-LR were determined to be (2.25⯱â¯0.07)â¯×â¯1010 and (5.58⯱â¯0.42)â¯×â¯107â¯M-1s-1, respectively. Cl ⢠was the major RCS contributing to MC-LR elimination. The highest MC-LR degradation rate was observed at pH 8.0. Free chlorine, HO â¢, Cl ⢠and O3 together accounted for almost 95% of the MC-LR elimination. Hydroxyl- and chloro-MC-LR were generated in the process, followed by dechlorination, dehydration and cleavage of cyclic structures in MC-LR. Aldehyde- and ketone-MC-LR byproducts were also observed. The destruction of dienes led to a great reduction in MC-LR's toxicity. MC-LR removal in natural water samples under natural sunlight irradiation with free chlorine was demonstrated with limited formation of disinfection byproducts. The solar/chlorine process is an energy-efficient approach for MC-LR control, especially suitable for rural areas or where algal blooming threatens.
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Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Contaminantes Químicos del Agua
/
Purificación del Agua
Límite:
Humans
Idioma:
En
Año:
2019
Tipo del documento:
Article