Purate™ Chemistry

How does ClO2 compare to other technologies?

Chlorine dioxide (ClO2) is a remarkable molecule that performs well when compared to other technologies.

Chlorine dioxide vs. Chlorine
Safety concerns with chlorine gas have prompted many to switch to alternate products such as chlorine dioxide (ClO2).

Chlorine, as chlorine gas or sodium hypochlorite has been used for years as a pre-oxidant and primary disinfectant. However, its use continues to decrease because of the problems associated with the formation of by-products of concern. Chlorine is a weaker antimicrobial than ClO2, particularly at pH levels above 7. Although chlorine is generally less expensive per unit weight, the overall treatment cost with ClO2 is often less because of its increased efficacy. Chlorine can cause odor problems, but ClO2 can solve taste and odor problems.

Because ClO2 produced less by-products of concern, it is often used at the beginning of the water plant as a pre-oxidant, often for control of Fe and Mn.

Chlorine dioxide vs. Ozone
The strong oxidizing potential of ozone leads to the formation of bromate, a regulated carcinogen in drinking water.

Ozone is a stronger antimicrobial than ClO2. However, in water sources containing bromide, the allowable dose of ozone can be severely limited by the bromate limits. Because of the high reactivity of ozone, a residual is short-lived and difficult to measure. Plus operating and maintenance costs for ozone systems are high.

Chlorine dioxide systems are much less expensive to install.

Chlorine dioxide vs. UV
UV final treatment combined with chlorine dioxide (ClO2) pre-treatment can be a very effective water treatment solution.

Both UV and ClO2 require short contact times for inactivation of microorganism and are unaffected by ammonia in the water. UV systems are costly to install, operate and maintain. A back-up power supply is often specified for a UV system which adds significant cost to the system because of the high power demand.

Because UV treatment provides no residual disinfectant, bacteriological testing is require to determine the effectiveness, taking more than 24 hours to complete.

Name: Chlorine Dioxide
Synonyms: "Chlo-2", chlorine oxide, chlorine peroxide
Formula: ClO2
Molecular Weight: 67.4518
Cas No. 10049-04-4
Bond Angle: 117.5°
Bond Length: 0.147 nm
Dipole Moment: 5.95x10-30 C*m
Acentric Factor: 0.35638

Competitors - Low Efficiency

Some chlorite-based generators can achieve 95% efficiency when properly calibrated. However, three-chemical generators (sodium chlorite + hypochlorite + HCl) quickly lose performance and require frequent adjustments and calibrations. As a result, they typically operate with lower efficiency.

One particular chlorite technology (sodium chlorite + HCl) can operate with high efficiency but with a low yield. Inherent in the chemistry is the need to use 5 molecules of sodium chlorite to produce 4 molecules of ClO2, making 80% the maximum possible yield. Because of low yields, this technology is economically limited to small accounts, typically less than 1 kg/hr.

Chlorine Dioxide generated by PURATE is globally accepted, CE certified (equipment only), EPA registered, FDA approved, BfR approved, Kosher (OU) certified and NSF 60 certified (equipment / precursor).

PURATE and sulfuric acid are NOT covered chemicals under Process Safety Management (PSM). Even though ClO2 is a covered chemical, it is generated on site and used immediately, so the threshold quantity (TQ) is never even approached.

ClO2 produced from PURATE avoids all of the PSM and Risk Management Program (RMP) requirements and associated costs.