Chlorine dioxide (ClO2) disinfection usually does not produce halogenated disinfection by-products, but the formation of the inorganic by-product chlorite (ClO2-) is a serious consideration. In this study, the ClO2- formation rule in the ClO2 disinfection of drinking water was investigated in the presence of three representative reductive inorganics and four natural organic matters (NOMs), respectively. Fe2+ and S2- mainly reduced ClO2 to ClO2- at low concentrations. When ClO2 was consumed, the ClO2- would be further reduced by Fe2+ and S2-, leading to the decrease of ClO2-. The reaction efficiency of Mn2+ with ClO2 was lower than that of Fe2+ and S2-. It might be the case that MnO2 generated by the reaction between Mn2+ and ClO2 had adsorption and catalytic oxidation on Mn2+. However, Mn2+ would not reduce ClO2-. Among the four NOMs, humic acid and fulvic acid reacted with ClO2 actively, followed by bovine serum albumin, while sodium alginate had almost no reaction with ClO2. The maximum ClO2- yields of reductive inorganics (70%) was higher than that of NOM (around 60%). The lower the concentration of reductive substances, the more ClO2- could be produced by per unit concentration of reductive substances. The results of the actual water samples showed that both reductive inorganics and NOM played an important role in the formation of ClO2- in disinfection."

****!!!!****!!!! (2019) "In this study, ClO2 alone and a ClO2/NaClO combination process were carried out to evaluate the algae removal efficiency of the treatment and the formation of disinfection by-products (DBPs: chlorite, chlorate, trihalomethanes and haloacetic acids) for high algae-laden water with 124.16 µg L-1 chlorophyll a (Chl.a) content. The results show that disinfection with 1.5 mg L-1 ClO2 alone results in a ClO2- concentration exceeding 0.7 mg L-1. ClO2 preoxidation/ClO2 disinfection is applicable for the control of effluent quality, but the ClO2- concentration still has an excessive risk when using 0.8 mg L-1 and 0.6 mg L-1 ClO2 for the two process, respectively. In the ClO2/NaClO combination process, the ClO2- concentration is below 0.6 mg L-1, and trihalomethane (THM) and haloacetic acid (HAA) concentrations are lower than 60% of the maximum contaminant levels (MCLs) set by the World Health Organization (WHO). Further, the formation of ClO2- is more effectively controlled by NaClO preoxidation/ClO2 disinfection than ClO2 preoxidation/NaClO disinfection."

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"Following the principal modes of disinfection, typically 70% of the initial dose of chlorine dioxide is converted to chlorite. Thus the initial dosage of chlorine dioxide should not exceed 1.4 ppm to prevent exceeding DBP formation."

"Between pH 5 and 9, 4.5 mg/L of chlorine dioxide instantaneously oxidizes 1 mg/L of a mercaptan (expressed as sulfur) to the respective sulfonic acid (RSO3H)/sulfonate compound, destroying the mercaptan odor. Similarly, chlorine dioxide reacts with organic sulfides and disulfides, destroying the original odor. Organic disulfides are split at the sulfur atoms and oxidized to sulfonic acid. The oxidation of amines with chlorine dioxide depends on the pH of the reaction mixture and the degree of substitution of the amine. Between pH 5 and 9, an average of 10 mg/L of chlorine dioxide oxidizes 1 mg/L of a tertiary aliphatic amine (expressed as nitrogen), destroying the amine odor. At pH above 7, an average of 5 mg/L of chlorine dioxide oxidizes 1 mg/L of a secondary aliphatic amine (expressed as nitrogen), removing all traces of amine odor. The higher the pH of the reaction mixture (chlorine dioxide and tertiary and/or secondary aliphatic amines), the more rapidly oxidation proceeds."

(2020).

".The degradation efficiency was shown positively correlated to the concentration of ClO2 and reaction time; while the effect of reaction temperature and pH is slight."

"regulations specify that the tap water should have a pH level of 6.5 to 9.5. Water leaving the treatment works should have a pH of 7 and 9."

"Chlorine dioxide was more effective against Aphanomyces sp. than S. diclina and A. bisexualis. Three days of immersion in chlorine dioxide >100 ppm inhibited hyphal growth of S. diclina and A. bisexualis, and concentrations >50 ppm inhibited growth of Aphanomyces sp. Immersion in 500 μg/ml chlorine dioxide for 1-4 h killed the hyphae and concentrations of 32 to 63μg/ml inhibited germination and killed zoospores of all three strains. The result suggest that treatment of hatchery water with 63μg/ml of chlorine dioxide for 10 min can control the zoospores but does not inhibit the growth of fungal hyphae of these strains. We conclude chlorine dioxide is an effective antifungal agent on both the hyphal and zoospore stages of S. diclina, A. bisexualis and Aphanomyces sp."

"using the homemade compound chlorine dioxide generator to sewage sterilization. Through the detection of total bacterial count and fecal coliform bacteria in sewage sterilization with compound chlorine dioxide, finding out the optimal dosing concentration, contacting time, pH, stirring speed and other significant parameters. The results show that the optimal dosing concentration is 5mg/L, the contacting time is 4min, the stirring speed is 90r/min and the pH value has little effect. Under the condition, the compound chlorine dioxide can reach good disinfection effect, providing the technical basis for the development of disinfection process in the future. "

"Good activation of sodium chlorite will result in 60–70% active chlorine dioxide. This will leave 30– 40% of un-activated residual sodium chlorite". {Note: In earlier article on Oxine, BVS indicated that Oxine's sodium chlorite conversion % is a different range than this. http://midwestpoultry.com/wp-content/uploads/Thoreson-Ross-Chlorine-Dioxide-Why-It-Is-Best-for-Water-Sanitation.pdf}

in drinking water treatment "typically 70% of the initial dose of chlorine dioxide is converted to chlorite" "initial dosage of chlorine dioxide should not exceed 1.4 ppm to prevent exceeding DBP formation"{ "Iron Removal -1.2 mg / mg iron -immediate Manganese Removal -2.5 mg / mg manganese -immediate Sulfide Removal -5.8 mg / mg H2S Taste and Odour -1 -2.5 mg/L 10 minutes contact time Bacteria Inactivation -1 to 5 mg/L 5 minutes contact time Giardia -1.5 to 2.0 ppm 60 minutes contact time Cryptosporidium -Approx 8-16 times giardia" "Acid / Chlorite Method. Sodium chlorite can be supplied in two concentrations. 25% and 7.5%, depending on the generation rate required. Acid solution is also supplied at two concentrations, 32% and 9%to correspond to the sodium chlorite solution. No secondary storage is required -thus no intermediate decomposition of chlorine dioxide to chlorite" "DBP Formation Potential -Chlorine Dioxide does not form halogenated byproducts, THM and HAA5 constituents when it interacts with NOM, as long as no excess chlorine is present from generation. Chlorine Dioxide does form Chlorite and Chlorate, both have limits, however chlorate is not as problematic as chlorite." "if initial demand and dosage is kept below 1.4 ppm, then no DBP formation over the set guidelines" "Extended storage of chlorine dioxide solution can contribute to byproduct formation." "

"statistically-based mode1 equations capable of predicting chlorine dioxide consumption, chlorite and chlorate formation when dosing with chlorine dioxide. These equations were developed in temu of pH, temperature, chlorine dioxide concentration, reaction the and water organic content."

{Combined with Citric Acid to reduce hard water mineral scaling} "concentration of 1500 mg/l chlorine dioxide. On wells that demonstrated significant hard water scaling, acetic or citric acid was applied with the chlorine dioxide to help dissolve inorganic carbonate scale deposits." "A single chlorine dioxide treatment achieved a 100 percent success rate for the sustained elimination of microbial contamination in the wells" "chlorine dioxide is a true gas that is a relatively stable oxidant, reacting only with reduced compounds such as sulfides, phenols, and biomass. This allows it to penetrate into the formation, kill bacteria, destroy biomass, and oxidize contaminants without forming undesirable by-products. Because chlorine dioxide does not become less soluble in the presence of acids, it can be safely used in conjunction with them to achieve treatment of multi-component matrix damage. As it is a well-established EPA-registered biocide for use in drinking water and food, regulatory considerations are limited to local permitting requirements."