Made On Site. Dosed Precisely. Run Safely.
Chlorine dioxide generators for municipal water plants, cooling towers, food and beverage plants, pulp mills and oilfield water. Chlorine dioxide is made where it is used, so the generator, its chemistry and its controls decide how well the treatment works.
Chlorine dioxide is not shipped as a compressed gas. It is potentially explosively unstable above 10 percent by volume in air, so it is made on site, at low concentration, and used straight away as a dilute solution in water.
A generator is the machine that does that. It meters precursor chemicals into a reactor, makes the chlorine dioxide, dilutes it and hands it to the water. What changes from one generator to the next is the chemistry, the controls and the safety systems around it.
Sodium chlorite solution and an acid, chlorine or hypochlorite, held in separate tanks with their own containment.
Pumps or eductors feed each chemical to the reactor in a set ratio. The ratio decides how much of the chlorite becomes chlorine dioxide.
The chemicals meet in a reactor column. Chlorine dioxide forms in the column as a solution.
Dilution water carries the product out as a dilute solution, ready to dose.
The solution goes into the water main, tower basin, wash line or process tank through an injection fitting, with a sample tap downstream.
The chemistry decides what you store, what you feed and what can go wrong. Pick the generator that fits the chemicals your site can handle.
Sodium chlorite solution and an acid, usually hydrochloric, are metered into a reactor and mixed with dilution water. It needs two chemicals and two feed pumps, and no gas cylinders.
Chlorine, as gas or as chlorine water, reacts with sodium chlorite in the reactor. Treatment plants that already feed chlorine often use this route because the chlorine system is already on site.
Sodium hypochlorite and hydrochloric acid first react to make chlorine in the generator, and that chlorine then reacts with the sodium chlorite. It avoids chlorine gas cylinders while using the chlorine-chlorite chemistry.
A direct current passes through a cell and chlorine dioxide forms there, so no acid is fed. Suppliers point to consistent output and product purity.
Chlorate-based generation, using sodium chlorate with hydrogen peroxide and sulfuric acid, is described in the EPA's guidance manual as an emerging technology for drinking water.
Plants use chlorine dioxide mostly to oxidize iron and manganese and to improve taste, odor and color. It is less likely than free chlorine to form disinfection byproducts, and it inactivates some chlorine-resistant organisms.
Chlorine dioxide is one of the oxidizing biocides used in cooling water systems, including where the aim is to control Legionella and biofilm.
Aqueous chlorine dioxide has been approved by the FDA since 1998 for sanitizing fruit and vegetable surfaces, and processors also use it in wash and process water. Poultry and meat plants have used it in wash and chill water, with limits set by current USDA and FDA rules.
Eight points to settle before you ask for prices. The first one, which chemicals your site can store and handle, usually narrows the choice more than any other.
A plant with chlorine already on site will look at chlorine-chlorite. A plant with no gas will lean to acid-chlorite or three-chemical. Match the generator to the chemicals you can store and handle.
Size to the peak dose and ask how low the generator can run without losing yield. Plants with varying flow need good turndown.
The EPA's guidance manual puts a typical specification at yield above 95 percent with excess chlorine under 2 percent by weight. Ask for a supplier's figure and how it was measured.
In drinking water, chlorite is the main end product and chlorate follows. The dose has to leave you inside the limits, and chlorate is hard to remove after it forms.
Flow-paced or analyzer-controlled feed, residual analyzers, and alarms. Ask what the generator does when a chemical runs out or a pump fails.
Leak detection, containment, interlocks, dry-run protection and clear shutdown behavior. Ask where the product is made, at what strength and under what pressure.
Wetted parts, tubing and fittings suited to chlorite, acid and chlorine dioxide, and a skid that fits the room and the ventilation.
Spare parts, calibration, training and the chemical supply chain.
Four numbers come up in almost every specification. The first two are the US EPA limits that govern drinking water. The third is the workplace limit for air. The fourth is why the gas is never stored.
| What | Limit | Set by |
|---|---|---|
| Chlorine dioxide in drinking water | 0.8 mg/L | US EPA maximum residual disinfectant level (MRDL) |
| Chlorite in drinking water | 1.0 mg/L | US EPA maximum contaminant level (MCL), average of a 3-sample set |
| Chlorine dioxide in workplace air | 0.1 ppm | OSHA permissible exposure limit, 8-hour time-weighted average |
| Chlorine dioxide gas in air | above 10% by volume | Potentially explosively unstable, per the chemical maker's safety bulletin |
Information only. This guide is general and educational. It is not engineering, safety, legal or professional advice and does not replace the manufacturer's instructions, your permits or applicable regulations. Verify before relying on it. Read the full disclaimer.
It is a skid or cabinet that makes chlorine dioxide on site from precursor chemicals, then dilutes it and feeds it into a water or process stream. Chlorine dioxide is not shipped as a compressed gas, so it is made where it is used.
Metering pumps or eductors feed sodium chlorite and a second chemical into a reactor. Chlorine dioxide forms in the reactor and leaves as a dilute solution with the dilution water. Controls pace the feed to flow or to an analyzer reading.
Acid-chlorite, chlorine-chlorite, three-chemical (hypochlorite, acid and chlorite) and electrochemical. The first three differ in the chemicals you feed. The electrochemical type makes chlorine dioxide at an electrode cell.
Acid-chlorite and three-chemical systems avoid chlorine gas cylinders. Electrochemical units remove the acid as well. The right one depends on which chemicals you can store, handle and get delivered.
The EPA sets a maximum residual disinfectant level of 0.8 mg/L for chlorine dioxide and a maximum contaminant level of 1.0 mg/L for chlorite. Systems that use chlorine dioxide sample the entry point for both every day.
In drinking water, chlorite is the main end product of chlorine dioxide. The EPA manual says roughly 50 to 70 percent of the chlorine dioxide used ends up as chlorite, with chlorate and chloride making up much of the rest. That is why the dose is capped.
It can be if handled badly. The gas is potentially explosively unstable above 10 percent by volume in air, and OSHA sets a workplace limit of 0.1 ppm over an 8-hour shift. Generators are built to keep concentrations low and the chemicals separate.
It is one of the oxidizing biocides used in cooling water systems. A water treatment professional should set the dose, the sampling plan and the response procedure for your tower.
Start with the peak dose in mg/L, the flow it applies to, and how low the dose can run. Suppliers size the generator from those three numbers and from the chemistry you pick.
Ask for the yield and residual chlorine figures and how they were measured, the control and alarm logic, the shutdown behavior on a chemical or power failure, the wetted materials, the chemical supply, and what service they provide.
Tell us what water or process you treat, the dose and flow, and the chemicals your site can store. You will get a reply, usually within one business day.