This article discusses how dosing chlorine and chlorine dioxide concurrently provides excellent disinfection inactivation and limits chlorite formation. This was done when Aurora (Colorado) Water's 8...

"determine the effect of granular activated carbon (GAC) filtration and sulfur-based reducing agents on chlorite and chlorate ions in water. It is concluded that neither GAC filtration nor sulfur-based reduction is a feasible means of removing chlorine dioxide by-products."

****!!!!**** {Data in tables is based on limited sources} "A review of data from Hoff (1986) indicates that the disinfection efficiency of chlorine dioxide for bacteria and viruses increases approximately 2 to 3 gold as pH increases from 7 to 9." "pg 378 Table of CT Values for Inactivation of Giardia Cysts by Chlorine Dioxide in pH 6-9" "[page 379] Table of CT Values for Inactivation of Viruses by Chlorine Dioxide in pH 6-9"

Slide 1 Cl2 vs. ClO2

Chlorine dioxide (ClO2) is often used as an oxidant to remove taste, odor and color during water treatment. Due to the concerns of the chlorite format…

"in-depth analysis of the effects of UV wavelength on the simultaneous removal of ClO2- and OMPs in water."

"sequential ClO2-UV/chlorine process was effective for the removal of 12 micropollutants. ClO2 pre-treatment reduced the formation of disinfect byproducts (DBPs) in the UV/chlorine process. Compared to the UV/chlorine process, ClO2 pre-treatment (1.0 mg L-1) decreased the formation of the 6 DBPs by 25.1-72.2%; and decreased the formation potential of the 6 DBPs by 13.9-51.8%. Moreover, ClO2 pre-treatment reduced the concentration of total organic chlorine by 19.8%. ClO2 pre-treatment affected the UV/chlorine process in different ways. Firstly, ClO2 pre-treatment generated chlorite, which dominantly served as a scavenger of chlorine radical (Cl) and hydroxyl radical (HO). Secondly, ClO2 pre-treatment decreased the reactivity of natural organic matter (NOM) towards radicals. Finally, ClO2 pre-treatment altered the properties of NOM, in terms of reducing the electron-donating capacity and aromaticity of NOM (SUVA254), and slightly reducing the average molecular weight of NOM."

Chlorine dioxide (ClO2) has emerged as a promising alternative to free chlorine for water disinfection and/or pre-oxidation due to its reduced yields of chlorinated disinfection byproducts. ClO2 decomposes to form chlorite (ClO2-), which influences the following advanced oxidation processes (AOPs) for micropollutant abatement in drinking water. This study aims at investigating the effects of ClO2- on the concentrations of reactive species (e.g., radicals and ozone) and on the formation of chlorate in the UV/chlorine AOP. Results showed that the concentration of ClO· in the UV/chlorine process remarkably decreased by 98.20-100.00% in the presence of ClO2- at concentration of 0.1-1.0 mg·L-1 as NaClO2. The concentrations of HO· and ozone decreased by 42.71-65.42% and by 22.02-64.31%, respectively, while the concentration of Cl· was less affected (i.e., 31.00-36.21% reduction). The overall concentrations of the reactive species were differentially impacted by ClO2-'s multiple roles in the process. UV photolysis of ClO2- generated HO· but not Cl·, ClO· or ozone under the drinking water relevant conditions. ClO2- also competed with chlorine for UV photons but this effect was minor (< 1.0%). The radicals/ozone scavenging by ClO2- outcompeted the above two to lead to the overall decreasing concentrations of the reactive species, in consistency with the kinetic model predicted trends. ClO2- reacted with radicals and ozone to form chlorate (ClO3-) but not perchlorate (ClO4-). HO· played a dominant role in ClO3- formation. The findings improved the fundamental understanding on micropollutant abatement and inorganic byproduct formation by the UV/chlorine process and other AOPs in ClO2--containing water.

Chlorine dioxide when used as an effective disinfectant forms undesirable disinfection by-products, i.e. chlorite and chlorate ions.

"purification process of purifying Philippine clams in the oxygenated state with 4 times of disinfected seawater...) was explored, and the water was changed once for 8 hours, and the purification time was 24 hours. The pilot test of the process can reduce the number of E. coli population in the Philippine Hazai intestine... and the sterilization rate reaches about 95%, the sand content is reduced from 65mg/100g to 23mg/100g, and the volatile salt-based nitrogen rises from 3.8mg/100g to 5.8mg/100g," "phenolic compounds denature proteins and make microorganisms inactive, and also different from chlorine biochlorination and inactivity. When it comes into contact with microorganisms, it releases new ecological oxygen and hypochlorous acid molecules and produces a powerful bactericidal and disinfection effect. This strong oxidation effect makes the amino acids in microorganisms oxidize and decompose, so as to inhibit their growth and kill them. Its residues water, trace chloride, carbon dioxide, organic sugar and other non-toxic and harmless substances." "According to the experimental results of Chen Youlin [2], the mass fraction of chlorine dioxide only needs to be 10× 10-6 action for 5 minutes to completely kill E. coli, mass fraction 10× 10-6 action to completely kill Staphylococcus aureus, mass fraction 100× 10-6 action 10min to kill spore bacteria, mass fraction 500× 10-6 for 2min to destroy hepatitis B virus (HBSAG); Chlorine dioxide can also have a special decomposition effect on cyanide, etc"

Cooling systems offer an ideal environment for microbiological fouling. Take steps now to look for and treat scaling and fouling.

"for the selective oxidants, the competition disappears rapidly after the ERMs present in EfOM are consumed. In contrast, for hydroxyl radicals, the competition remains practically the same during the entire oxidation. Therefore, for a given oxidant dose, the selective oxidants were more efficient than hydroxyl radicals for transforming ERMs-containing micropollutants, while hydroxyl radicals are capable of transforming micropollutants even without ERMs"

****!!!! When a water tap is opened, small amounts of chlorine dioxide diffuse into the air and combine with existing household odors. All homes have volatile organic compounds (VOCs) in the ambient air produced by scented products (soaps, candles, air fresheners, incense, potpourri), cleaning agents or solvents, paint, carpet, furnishings, fresh flowers or wreaths, and many other common household items. The VOC/chlorine dioxide combination odors have been described as smelling like fuel oil, kerosene, chemicals or cat urine, to name the most common. Studies have not identified any health concerns associated with this combined odor. The strongest odors are associated with installing new carpet, upholstered furniture or draperies andinterior painting. The odor will continue until the level of VOCs decreases (new smell goes away). This can take from a few weeks up to several months to dissipate depending on the situation, type of materials, amount of ventilation, etc.

{At bottom, includes links to many highly valuable papers}

The sulfate-reducing bacteria and related corrosion can be inhibited by charge-reversal surfactant antibiotic material. "There are many SRB antibiotics used in petroleum exploitation, including quaternary ammonium surfactants, chlorine dioxide"

"we found that UV photolysis after ClOsub2/sub disinfection can effectively eliminate both ClO2..."

Photolysis of ClO2 by UVC radiation occurs in several drinking water treatment scenarios (e.g., pre-oxidation by ClO2 with post-UVC disinfection or a multi-barrier disinfection system comprising ClO2 and UVC disinfection in sequence). However, whether micropollutants …

****!!!!****!!!!**** " In practice, based on a 10% chlorine excess compared with the stoichiometry and a 95% efficiency, 1.41 g of pure sodium chlorite and 0.61 g of chlorine will be required to produce 1 g of CℓO2." "obtained by oxidizing a solution of sodium chlorite using chlorine or hydrochloric acid" "Sodium chlorite solutions can be prepared from sodium chlorite powder. Water that has first been softened will need to be used to prevent calcium carbonate from precipitating."

"Phenols... Below pH 10, a minimum of 1.5 mg/L of chlorine dioxide oxidizes 1 mg/L of phenol to benzoquinone." "Algae... adding chlorine dioxide to the reservoir at night (to prevent decomposition of chlorine dioxide by sunlight). The algae killing action is fast enough to be effective before the sun rises. A dosage of 1 mg/L " "Sulfides - it does rapidly oxidize hydrogen sulfide to sulfates in the pH range 5-9. Between pH 5-9, a minimum of 3.36 mg/L of chlorine dioxide should be used to instantly oxidize 1 mg/L of sulfide to sulfate."

"Our experimental results show that the oxidation process is a second order overall and a first order with respect to C1O2 and MC-RR. The activation energy of MC-RR degradation by C1O2 is 53.07 kJ/mol. The rate constant k of the action can be increased by increasing temperature and decreasing pH value and ranged from 6. 11x102 L/(mol.min) to 5.29x 102 L/(mol-min) at pH from 3.44 to 10.41 at 10 ℃. Reaction products were determined to be organic and volatile, because they could be almost removed from aqueous solution by heating for 15 min at 60 ℃. In addition, the main oxidation products have m/z values of 1072 and are identified as dihydroxy isomers of MC-RR."

"HAAs [haloacetic acids] from chlorine dioxide disinfection process are mainly DCAA, CBAA and DBAA" "ClO2 is a strong oxidant rather than chlorinating agent, which means during disinfection, small amounts of THMs are generated compared to chlorine or chloramine disinfection. However, ClO2 disinfection process produces more HAAs (primarily DCAA, CBAA and DBAA). ClO2 inorganic disinfection byproducts ClO-2, ClO-3 and BrO-3 have high potential toxicity at high-dose or high concentrations, wherein ClO-2 can cause hemolytic anemia"

(1969)

The sulfonamide antibiotic sulfamethoxazole (SMX) is a widely detected micropollutant in surface and groundwaters. Oxidative treatment with e.g. ozone or chlorine dioxide is regularly applied for disinfection purposes at the same time exhibiting a high potential for removal of micropollutants. Espec …

Diclofenac (DCF), a synthetic non-steroidal anti-inflammatory drug, is one of the most frequently detected pharmaceuticals in the aquatic environment."

"The precursor of chlorine dioxide (9) is activated with an acid-based product delivered into the DWLS, followed by a change of water pressure when animals are drinking water. So, the activation will occur just when it is needed: on-demand. This final product will help to control and manage biofilm formation. Removing biofilm and reducing biofilm formation helps to manage the negative impact on the taste and odor... Additionally, chlorine dioxide binds mineral elements, such as iron and manganese... These minerals have also been noted as fundamental precursors for bacteria growth"

"[To generate chlorine dioxide:] Theoretically, 1 lb of chlorine gas is required for each 2.6 lb of sodium chlorite. However, an excess of chlorine is often used to lower the pH to the required minimum of 3.5 and to drive the reaction to completion. Sodium hypochlorite can be used in place of the gaseous chlorine to generate chlorine dioxide. This process requires the addition of sulfuric or hydrochloric acid for pH control." "The chemical behavior and oxidation characteristics of aqueous chlorine dioxide are not well understood because of the difficulty in differentiating aqueous chlorine-containing species."

"A case study on Fuller's Brewery [which implemented a chlorine dioxide dosing system] who enlisted our expertise and unique sensor technology to keep their leading product natural and chemical free." "Our disposable sensor technology utilises chronoamperometry which eliminates the interferences typically associated with colorimetric methods. As colorimetric test methods rely on light transmission for the test function, they do not tolerate highly coloured or turbid samples. Chronoamperometry does not rely on light or colour and therefore overcomes these challenges associated with reagent-based testing."