Chemical Dosing Applications by Industry: Which Chemicals Each Sector Uses

Chemical dosing applications cover almost every plant that handles water or process liquids, and what goes into the tank depends on the job: coagulation, disinfection, scale and corrosion control, pH adjustment, or removing a specific contaminant. Change the chemical and the pump head material, piping, tank and make-up method may all have to change with it. This guide walks through the main chemical dosing applications by industry, lists the chemicals each one commonly uses, and explains what those chemicals mean for the equipment. It is written for process designers, buyers and operators new to a site. Dose rates and concentrations always come from jar tests or commissioning, so no fixed numbers are given here.

Where chemical dosing applications are found

Typical users include drinking water plants, municipal and industrial wastewater plants, cooling water systems, boiler houses, pure water and reverse osmosis systems, metal finishing and PCB factories, food and beverage plants, pharmaceutical sites, and the oil, gas and petrochemical sector. Each of these chemical dosing applications has its own chemical list.

Municipal water and wastewater

This is the largest group of chemical dosing applications.

1. Coagulants such as polyaluminium chloride (PAC), ferric sulfate and aluminium sulfate, which destabilize fine suspended solids.
2. Flocculants, mainly polyacrylamide (PAM), which bind small flocs into larger ones and are also used in sludge dewatering.
3. Disinfectants such as sodium hypochlorite and chlorine dioxide for final effluent or drinking water.
4. Phosphorus removal chemicals, iron or aluminium salts.
5. External carbon sources such as sodium acetate when denitrification is short of carbon.

PAC is corrosive and crystallizes easily. PAM is viscous and must be dissolved and aged before dosing. For the role and order of each chemical, see wastewater dosing process.

Cooling towers and boilers

Cooling water programs rely on three families: scale inhibitors, corrosion inhibitors and biocides, sometimes with acid for pH control. Biocides are either oxidizing, commonly sodium hypochlorite, or non-oxidizing organic products, and the two are often alternated. System layout is covered in industrial cooling water treatment.

Boilers use a different set: phosphate for internal scale control, oxygen scavenger in the feedwater, and an alkalizing agent or ammonia to hold pH and protect piping. Boiler injection points run at high pressure, so pump rated pressure must sit comfortably above actual injection pressure. Details are in boiler dosing chemicals.

Reverse osmosis and pure water

RO pretreatment usually doses four things: antiscalant to keep the membrane surface clean, a reducing agent such as sodium bisulfite to remove free chlorine, acid for pH adjustment, and a non-oxidizing biocide. Doses are small, so the metering pump often works at the low end of its range. Check turndown when sizing.

Metal finishing and PCB effluent

Plating and PCB wastewater is complex, and so is the chemical list among industrial chemical dosing applications. Cyanide streams are oxidized with sodium hypochlorite. Chromium streams are first treated with sodium metabisulfite or bisulfite to reduce hexavalent chromium to trivalent. Caustic or lime then raises pH to precipitate metals, a heavy metal precipitant is added where needed, and PAM helps settling.

Strong acids, strong bases and oxidizers all appear in the same room, so check pump head and pipe materials chemical by chemical. Ventilate the dosing room and keep acid, caustic and hypochlorite storage apart to avoid toxic gas if they mix.

Food, pharma, oil and gas

Food, beverage and pharmaceutical plants dose caustic, acid and sanitizer for CIP cleaning, plus ingredient additives in batching. Wetted parts in product contact must be sanitary grade.

In oil, gas and petrochemical chemical dosing applications, typical chemicals are corrosion inhibitors, scale inhibitors, demulsifiers and biocides. Injection pressures are often high and some sites are hazardous areas, so hydraulic diaphragm or plunger pumps are common, with explosion protected electrics.

How dosing system chemicals shape the equipment

For any of these chemical dosing applications, once the chemical is known, check four properties:

• Corrosiveness, which sets head, ball, seal and pipe materials.
• Viscosity. PAM and similar products need slow strokes, larger heads and bigger suction lines.
• Gassing. Hypochlorite and hydrogen peroxide release gas in the head, so choose a head with a degassing valve.
• Crystallization. PAC and phosphate can precipitate in the cold or when the pump stops, so plan flushing and insulation.

Where one package doses several chemicals, give each its own tank and pump, and never share lines.

Matching pump type to chemical dosing applications

Pump type follows the duty more than the industry. For small doses of clean liquids at low pressure, as in many RO and pool chemical dosing applications, a solenoid metering pump is usually enough and easy to adjust. Larger flows, continuous duty and moderate pressure, which is typical in wastewater and cooling water, point toward a motor-driven mechanical diaphragm pump. High pressure injection, such as boiler feedwater or wellhead inhibitor, calls for a hydraulic diaphragm or plunger pump. A common mistake is choosing on flow alone and finding later that the pump cannot hold the injection pressure, so always state both. Compare the main options in our solenoid metering pumps range before you send an enquiry.

Conclusion

Chemical dosing applications are defined by industry and treatment goal. Water and wastewater center on coagulation, flocculation and disinfection; cooling water and boilers on scale, corrosion and pH; RO on membrane protection; plating and PCB effluent on cyanide oxidation, chromium reduction and metal precipitation; oil and gas on inhibitor injection at high pressure. Once the chemical is fixed, head material, make-up method and accessories follow. See our dosing skids, then send the chemical name, concentration, dose rate and injection pressure and contact our engineers to check the configuration.

FAQ

Can one dosing system handle several chemicals?

Yes, as a multi-tank, multi-pump package. Give each chemical its own tank and pump and keep lines separate to prevent reactions.

Who decides which chemicals to dose?

Usually the process designer or chemical supplier, based on water quality. The equipment supplier then selects materials and pump type to match.

We changed chemical. Can we keep the old pump?

Only after checking compatibility of the head, seals and piping with the new product, plus its viscosity and gassing behavior. If they do not match, change the head or lines.

How is the dose rate set?

By jar testing or commissioning: start low and adjust against effluent results. Do not copy figures from another project.

Are there chemical dosing applications outside heavy industry?

Yes. Swimming pools, irrigation fertigation and livestock disinfection all use small dosing units. The principle is the same at a smaller scale.