Disinfection of simulated and real winery wastewater using sulphate radicals: Peroxymonosulphate/transition metal/UV-A LED oxidation

Abstract

The inactivation of four different microorganisms, Escherichia coli, Bacillus mycoides, Staphylococcus aureus and Candida albicans, inoculated in simulated (SWW) and real winery wastewaters (RWW), was assessed by the first time using free sulphate and hydroxyl radicals from photolytic (UV-A LED radiation; 370 nm) and metal [Fe(II) or Co(II)] activation of peroxymonosulphate (PMS). The experimental conditions tested were [PMS] ¼ 0.1 mM and [Fe(II) or Co(II)] ¼ 0.1 mM and pH 5.0 for the inactivation of microorganisms in SWW. However, due to the complexity of the water matrix, not unexpectedly, a fivefold concentration of reagents was required to inactivate the same organisms in RWW. In addition, compared to the bacteria, the fungus C. albicans presented a higher oxidative stress resistance to the treatments, and different experimental conditions were necessary to inactivate these cells. After 90 min, the photolytic activation of PMS through UV-A LED radiation achieved complete inactivation of E. coli, followed by S. aureus (z4 log) and B. mycoides (z3 log). Total inactivation of C. albicans was also achieved, but with higher dosages of PMS (10 mM). The metal activation of PMS through the use of a transition metal [Fe(II) or Co(II)] accelerated the inactivation rate, particularly in the first minutes of exposure time. These treatments reached between 1 and 3 log inactivation of microorganisms in the first minute of the experiment. In addition, the use of Co(II) as promoter in the activation of PMS, was more effective in the inactivation of S. aureus and C. albicans than activation with Fe(II). Since linear mathematical models do not adjust satisfactorily to inactivation results in all cases, different mathematical models were tested to fit the experimental inactivation data. In general, the Hom model correctly fits the inactivation results of the four microorganisms in all applied treatments. However, other models such as Biphasic and Double Weibull fit acceptably as well.

Inactivation of pathogenic microorganisms in freshwater using HSO5−/UV-A LED and HSO5−/Mn+/UV-A LED oxidation processes

“…The disinfection experiments were carried out with a RMS current intensity of 240 mA, corresponding to a UV irradiance of 23 W/m 2 and a photon flux of 5.53 Â 10 À7 E/s. The PMS/UV-A LED and PMS/M nþ /UV-A LED experiments were carried out using 0.1 mM as an optimal dosage of PMS and transition metals [Fe 2þ and Co 2þ ] in bacteria inactivation (Rodríguez-Chueca et al, 2017). However, the optimal dosage for removing C. albicans was 5 mM for PMS and 2.5 mM for transition metals.…”

Assessment of Sulfate Radical-Based Advanced Oxidation Processes for Water and Wastewater Treatment: A Review

“…The best results were obtained in those experiments in which a heterogeneous iron catalyst (ilmenite and pyrrhotite) was used, obtaining a complete disinfection in 20 min in both cases [120,123]. On the contrary, the combination of PMS/UV-A/Co 2+ has had a very low effect on the bacterial population [119], although these results may be due to interference in the treatment due to the composition of the wastewater used in the experiments, since the same process achieves within 60 min the complete elimination of microorganisms in other studies [124]. The best inactivation rate of S. aureus has been achieved using natural magnetic pyrrhotite (NP) as a heterogeneous catalyst [120].…”

“…To the best of our knowledge, only the effectiveness of metallic catalysis, both heterogeneous and homogeneous, for the activation of PMS and PS in order to eliminate microorganisms from water has been analysed. Specifically, iron (in various forms and oxidation states) is the most commonly used transition metal, followed by Co 2+ [35,[119][120][121][122][123][124]. It seems necessary to expand the number of activation methods assessed in order to choose the most effective one for full-scale implementation.…”

“…However, the inactivation of other bacteria such as S. aureus, B. mycoides, Enterococcus sp. and various fungus species has also been studied, although to a lesser extent [119,120,126]. Table 8 summarizes the results of all the reports published so far about sulfate-based AOPs applied in disinfection.…”

“…The best inactivation rate of S. aureus has been achieved using natural magnetic pyrrhotite (NP) as a heterogeneous catalyst [120]. Among the homogeneous catalysts, Co 2+ has been the most effective activator [119,124]. In the case of the elimination of B. mycoides, the treatments carried out with both Co 2+ and Fe 2+ have provided similar results, achieving a maximum disinfection rate still far from complete disinfection (3.4 log) [119,124].…”