Chemical Dosing Systems

A chemical dosing system is a package of equipment that accurately meters and injects a controlled quantity of a treatment chemical into a water or process stream at the required rate and point of application. It typically comprises a chemical storage tank, a metering pump, injection pipework and fittings, secondary containment, level monitoring and a control system that adjusts the dose rate in response to process flow or a measured water quality parameter. Chemical dosing systems are used at multiple points throughout water treatment, wastewater treatment and industrial process plants to achieve disinfection, pH control, scale prevention, coagulation, dechlorination and many other treatment objectives.

IWTE designs and supplies dosing systems for a wide range of treatment chemicals including antiscalants and scale inhibitors, sodium hypochlorite and chlorine solutions, acids and alkalis for pH correction, coagulants including ferric sulphate and aluminium sulphate, flocculant polymers, sodium bisulphite and sodium thiosulphate for dechlorination, fluorosilicic acid for fluoridation, nutrient solutions for biological treatment, corrosion inhibitors and heavy metal precipitation reagents. Materials of construction are selected for chemical compatibility with the specific chemical to be dosed.

Flow-proportional dosing is a control strategy in which the chemical dose rate is automatically adjusted in proportion to the instantaneous process flow rate, maintaining a constant chemical-to-water ratio regardless of flow variations. This ensures the correct dose is applied at all flow conditions, including low flow periods and peak demand periods, without manual adjustment. Flow pacing is the standard control mode for chemicals such as antiscalants, coagulants and chlorine, where the required dose is directly proportional to the volume of water being treated. IWTE integrates flow pacing control as standard in all dosing systems where the application requires it.

Closed-loop dosing control uses a measured process parameter, such as pH, chlorine residual, turbidity or conductivity, as a feedback signal to automatically adjust the chemical dose rate to maintain the parameter at a target set point. As the measured value deviates from the set point, the control system increases or decreases the pump output to correct it. Closed-loop control provides precise chemical addition that responds to changes in water quality and demand without manual intervention, and is the preferred control mode for pH adjustment, disinfection residual maintenance and other applications where tight parameter control is required.

IWTE designs all chemical dosing systems with secondary containment capable of holding the full volume of the chemical storage tank, preventing spills from reaching drains or the environment. Storage tanks are fitted with overfill prevention, vent pipes, safe-fill connections and level monitoring with high-level alarms. Chemical-resistant materials of construction are selected for all wetted components. Dosing pump enclosures and pipework routing are designed to minimise exposure risk during operation and maintenance. Safety documentation including chemical risk assessments, safety data sheet filing provisions and operator training materials are included in the system handover package.

IWTE selects metering pump technology based on the chemical, dose rate, discharge pressure and accuracy requirements of each application. Diaphragm metering pumps are the most widely used, offering reliable and accurate chemical addition for a broad range of chemicals at low to medium flow rates. Peristaltic pumps are preferred for aggressive acids, alkalis, concentrated slurries and abrasive chemicals where contact between the chemical and pump internals must be avoided. Piston pumps provide high accuracy at high discharge pressures for injection into pressurised process lines. All pumps are sized with appropriate turndown range to accommodate the minimum and maximum dose rates required.

Yes. IWTE designs multi-chemical dosing suites incorporating multiple independent dosing trains on a common skid frame, each with its own storage tank, metering pump, pipework and containment, controlled from a shared PLC panel. Multi-chemical suites are standard for water treatment plants requiring simultaneous dosing of several chemicals such as antiscalant, acid, coagulant and chlorine at different points in the process. Each dosing train is designed and operated independently to suit the specific chemical and dose rate requirements, while sharing a common control and monitoring interface.

Yes. Chemical dosing systems are included as an integral part of every complete water or wastewater treatment plant that IWTE designs and supplies. The dosing systems are engineered to match the plant flow rate, water quality, treatment objectives and chemical consumption requirements, with unified PLC and SCADA control across all dosing points. IWTE also supplies standalone dosing packages for integration into existing plants, including retrofit of additional chemical treatment stages or replacement of aging dosing equipment.