The risk of fungal pollution in drinking water has been paid attention. Solar/chlorine dioxide (ClO2) combined system is an environment-friendly, economical and efficient disinfection method, especially for countries and regions that are economically backward and still exposed to unsafe drinking water. In this paper, the kinetics, influencing factors, mechanism and regrowth potential of inactivated Aspergillus niger (A. niger) spores by solar/ClO2 were reported for the first time. The inactivation curve can be divided into three stages: instant inactivation within 1-2 min, slow linear inactivation and finally a tail. The synergistic factors produced by solar/ClO2 in terms of log reduction and maximum inactivation rate were 1.194 and 1.112, respectively. The inhibitory effect on the regrowth of A. niger spores inactivated by solar/ClO2 was also stronger than that by ClO2 alone. Strongly oxidizing reactive species produced by solar/ClO2 accelerated the accumulation of endogenic reactive oxygen species (ROS) caused by oxidation stress of A. niger spores, improving the inactivation ability of the system. The inactivation order of A. niger spores was: loss of culturability, accumulation of intracellular ROS, loss of membrane integrity, leakage of intracellular species and change of morphology. The inactivation performance of solar/ClO2 was better than solar/chlor(am)ine according to the comparison of inactivation efficiency and regrowth potential. Results also suggested that solar/ClO2 process was more suitable for the treatment of ground water sources.

This study investigates the effects of chlorine dioxide (ClO2) disinfection on the community structure, regrowth potential, and metabolic product secretion of disinfection-residual bacteria (DRB) in secondary effluent (SE), denitrification filter effluent (DFE), and ultrafiltration effluent (UE). Results show that ClO2 effectively reduces bacteria in SE and UE, achieving log removal values exceeding 3 at 1 mg/L within 30 min. A salient positive correlation (R2 > 0.95) exists between changes in total fluorescence intensity and disinfection efficacy. Post-treatment, Acinetobacter abundance increased in SE, while Pseudomonas decreased in DFE and UE. At lower ClO2 concentrations, Staphylococcus, Mycobacterium, Aeromonas, and Lactobacillus increased in DFE, but decreased at higher concentrations. After storage, bacterial counts in disinfected samples exceeded those in the control group, surpassing 105 CFU/mL. Despite an initial decline, species richness and evenness partially recovered but remained lower than control levels. Culturing DRB for 72 h showed elevated extracellular polymeric substances (EPS) secretion, quantified as total organic carbon (TOC), ranging from 5 to 27 mg/L, with significantly higher EPS in the disinfection group. Parallel factor analysis with self-organizing maps (PARAFAC-SOM) effectively differentiated water sample types and EPS fluorescent substances, underscoring the potential of three-dimensional fluorescence as an indirect measure of ClO2 disinfection efficacy.

OBJECTIVE: The disinfection efficiency of disinfectants differs in specific conditions. This study aimed to investigate the disinfection efficiency of commercial hydrogen peroxide, chlorine dioxide, and chlorine disinfectant on real field surfaces and provide data for precise disinfection.
METHODS: Simulated field disinfection and field disinfection methods were conducted to quantitatively evaluate the disinfection efficiency of hydrogen peroxide, chlorine dioxide, and sodium dichloroisocyanurate. The log10 reduction of biological indicators, Escherichia coli (ATCC 8099) and Staphylococcus aureus (ATCC 6538), was calculated. Next, the reduction in natural bacteria on the surfaces of a food production and processing workshop and a biosafety laboratory was determined.
RESULTS: The 3 commercial disinfectants evaluated were effective against E coli and S aureus, with a reduction of more than 3.00 log10 colony-forming units/mL tested for an exposure time of 15 minutes with 3.5% hydrogen peroxide, 100 mg/L chlorine dioxide, and 250 mg/L sodium dichloroisocyanurate. The natural load in the food production and processing workshop decreased by more than 90% using 10.5% hydrogen peroxide with an exposure time of 30 minutes. The same disinfection level in the biosafety level 2 laboratory was achieved by 500 mg/L chlorine dioxide at an exposure time of 60 minutes and 450 mg/L sodium dichloroisocyanurate at 60 minutes.
CONCLUSIONS: This study provides a reference for precise disinfection of surfaces in the food industry and biosafety laboratories.

Disinfection efficiency and disinfection byproduct (DBP) formation are two important aspects deserving careful consideration when evaluating different disinfection protocols. However, most of the previous studies on the selection of disinfection methods by comparing DBP formation were carried out under the same initial/residual dose and contact time of different disinfectants, and such a practice may cause overdose or underdose of a certain disinfectant, leading to the inaccurate evaluation of disinfection. In this study, a comprehensive and quantitative comparison of chlorine (Cl2) and chlorine dioxide (ClO2) disinfection was conducted with regard to their DBP formation under equal disinfection efficiency. The microbial inactivation models as well as the Cl2 and ClO2 demand models were developed. On such basis, the integral CT (ICT) values were determined and used as a bridge to connect disinfection efficiency and DBP formation. For 3-log10 and 4-log10 reductions of Pseudomonas aeruginosa, ClO2 had 1.5 and 5.8 times higher inactivation ability than Cl2, respectively. In the premise of equal disinfection efficiency (i.e., the ICT ratios of Cl2 to ClO2 = 1.5 and 5.8), the levels of total organic chlorine, total organic bromine, and total organic halogen formed in the Cl2 disinfection were significantly higher than those formed in the ClO2 disinfection. Among the 35 target aliphatic DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs) were the dominant species formed in both Cl2 and ClO2 disinfection. The total THM levels formed in Cl2 disinfection were 14.6 and 30.3 times higher than those in ClO2 disinfection, respectively. The total HAA levels formed in Cl2 disinfection were 3.5 and 5.4 times higher than those in ClO2 disinfection, respectively. Formation of the target 48 aromatic DBPs was much favored in Cl2 disinfection than that in ClO2 disinfection, and the formation levels was dominated by contact time. This study demonstrated that ClO2 had significant advantages over Cl2, especially at higher microorganism inactivation and lower DBP formation requirements.

BACKGROUND: Ensuring the safety of dental unit waterlines (DUWLs) has become a pivotal issue in dental care practices, focusing on the health implications for both patients and healthcare providers. The inherent structure and usage conditions of DUWLs contribute to the risk of biofilm formation and bacterial growth, highlighting the need for effective disinfection solutions.The quest for a disinfection method that is both safe for clinical use and effective against pathogens such as Staphylococcus aureus and Escherichia coli in DUWLs underscores the urgency of this research.
METHODS: Chlorine dioxide disinfectants at concentrations of 5, 20, and 80 mg/L were used to treat biofilms of S. aureus and E. coli cultured in DUWLs. The disinfection effectiveness was assessed through bacterial counts and culturing. Simultaneously, human skin fibroblast cells were treated with the disinfectant to observe changes in cell morphology and cytotoxicity. Additionally, the study included corrosion tests on various metals (carbon steel, brass, stainless steel, aluminum, etc.).
RESULTS: Experimental results showed that chlorine dioxide disinfectants at concentrations of 20 mg/L and 80 mg/L significantly reduced the bacterial count of S. aureus and E. coli, indicating effective disinfection. In terms of cytotoxicity, higher concentrations were more harmful to cellular safety, but even at 80 mg/L, the cytotoxicity of chlorine dioxide remained within controllable limits. Corrosion tests revealed that chlorine dioxide disinfectants had a certain corrosive effect on carbon steel and brass, and the degree of corrosion increased with the concentration of the disinfectant.
CONCLUSIONS: After thorough research, we recommend using chlorine dioxide disinfectant at a concentration of 20 mg/L for significantly reducing bacterial biofilms in dental unit waterlines (DUWLs). This concentration also ensures satisfactory cell safety and metal corrosion resistance.

Owing to their lack of outer skin, Chinese bayberries are highly susceptible to mechanical damage during picking, which accelerates bacterial invasion and rotting, shortening their shelf life. In this study, montmorillonite (MMT) was used to absorb an aqueous sodium chlorite solution embedded in a carboxymethyl cellulose sodium hydrogel after freeze drying, and the hydrogel was crosslinked by Al3+ ions. Al3+ hydrolyzed to produce H+, creating an acidic environment within the hydrogel and reacting with NaClO2 to slowly release ClO2. We prepared a ClO2 slow-release hydrogel gasket with 0.5 wt% MMT-NaClO2 and investigated its storage effect on postharvest Chinese bayberries. Its inhibition rates against Escherichia coli and Listeria monocytogenes were 98.84% and 98.96%, respectively. The results showed that the gasket preserved the appearance and nutritional properties of the berries. The antibacterial hydrogel reduced hardness loss by 26.57% and ascorbic acid loss by 46.36%. This new storage method could also be applicable to other fruits and vegetables.

[This corrects the article DOI: 10.3389/fpls.2022.887179.].

N-phenyl-N\'-(1,3-dimethyl butyl)-p-phenylenediamine-quinone (6PPDQ) currently arouses broad concerns because of its acute lethality to coho salmon and rainbow trout at environmentally relevant concentrations and the wide occurrence in runoff-impacted water. Investigation on the fate and transformation of 6PPDQ in various treatment processes is necessary for its risk assessment and control. Here, we explored the transformation of 6PPDQ during disinfection with its precursor 6PPD as a reference, focusing on kinetics, products, and toxicity variation. 6PPDQ readily reacted with hypochlorite and chlorine dioxide with second-order rate constants of 2580 ± 143 M-1 s-1 and 614 ± 52 M-1 s-1 (pH 7.0 and 25 °C), which are slightly lower than the reactions of 6PPD. We tentatively identified thirteen transformation products for 6PPDQ and eight for 6PPD in reaction with the two disinfectants. It seems that the quinone ring of 6PPDQ and the p-phenylenediamine moiety of 6PPD are reactive sites. The transformation of these compounds probably proceeds through Cl-substitution, ring cleavage, hydroxylation, and amine oxidation and hydrolysis. Tests with zebrafish embryos revealed that the transformation products of 6PPDQ could have higher eco-toxicity than the parent compound, while the toxicity of the 6PPD products remained nearly unchanged. The increased toxicity of 6PPDQ during disinfection highlights the necessity to substantially reduce its content before the disinfection of runoff-impacted water.

This chapter presents a systematic study of the inhibition effect of chlorine dioxide treatment alone and in combination with ultrasound treatment of Salmonella and the physiological metabolic processes within the treated cells. The low-power ultrasound (0.03 W/mL) significantly enhanced the effectiveness (110.00 %) of low concentrations of chlorine dioxide (0.25 mg/L) in inhibiting Salmonella, which, in turn, would significantly reduce the potential environmental impact. In addition, further studies found that low-power ultrasound may enhance the structural and functional damage of chlorine dioxide on Salmonella cell membranes (significant increase in permeability of the outer and inner cell membranes) and disrupt intracellular substance metabolism (small molecule and nucleotide metabolism) and energy metabolism (significant reduction in ATP content and ATPase activity) balance to improve the bacterial inhibitory effect of chlorine dioxide. The results of the study will provide a theoretical basis and methodological guidance for the implementation of \"cleaner production\" in the food industry.

Polylactic acid (PLA)-based microcapsules, capable of releasing chlorine dioxide (ClO2) upon exposure to moisture, have been developed for fruits and vegetables preservation. The microcapsules were prepared by emulsion solvent evaporation, utilizing PLA as the wall material, and NaClO2 as the core material. After optimization, NaClO2 microcapsules exhibited an encapsulation efficiency of 55.75% and an average particle size of 498.08 μm. Citric acid microcapsules were prepared using the same process, but with citric acid as the core material. When the two kinds of microcapsules were mixed, gaseous ClO2 was released in a highly humid environment. The release rate could be adjusted by temperature and the ratio between the two microcapsules, and the release period could be as long as 17 days at 20 °C. With a certain amount of microcapsules placed in the package of cherry tomatoes, the decay rate and weight loss rate of the fruits were reduced by 63 % and 34 %, respectively, compared to the control group. The microcapsules also helped to maintain the good appearance, hardness, and the content of total soluble solid content and titratable acid content of cherry tomatoes. Therefore, the PLA-based microcapsules have satisfied convenience and effectiveness for application in fruit and vegetables preservation.