Water Treatment Chemicals Guide

Function: Destabilize suspended particles by neutralizing their electrical charge, enabling aggregation and removal. 

Common chemicals: Aluminum sulfate (alum, Al₂(SO₄)₃), polyaluminum chloride (PAC), ferric chloride (FeCl₃), ferric sulfate (Fe₂(SO₄)₃), aluminum chlorohydrate (ACH). 

Applications: Potable water clarification, wastewater primary and tertiary treatment, phosphorus removal. 

Dosing considerations: Dose is determined by jar testing and is highly dependent on raw water quality, pH, temperature, and alkalinity. Overdosing increases sludge volume and can depress pH. 

Pump requirements: Corrosion-resistant liquid ends (PVDF, PTFE), high accuracy at variable flow rates, flow-proportional control capability. 

Milton Roy HAD and MAD metering pumps are proven in continuous coagulant dosing applications worldwide.

Function: Bridge destabilized particles into larger, heavier flocs for efficient sedimentation and filtration. 

Common chemicals: Cationic polyacrylamides (for sludge conditioning), anionic polyacrylamides (for clarification), nonionic polymers. 

Applications: Flocculation in potable and wastewater treatment, sludge conditioning before dewatering, dissolved air flotation (DAF). 

Dosing considerations: Polymers are shear-sensitive — excessive pump speed or turbulence degrades polymer chains and destroys flocculating capacity. Proper preparation (hydration, aging) is essential. 

Pump requirements: Low-shear pumping (peristaltic pumps preferred), accurate low-flow dosing, no check valves (polymer can clog them).

Function: Kill or inactivate pathogenic microorganisms to protect public health. 

Common chemicals: Sodium hypochlorite (NaOCl), calcium hypochlorite, chlorine gas, chlorine dioxide, chloramines. 

Applications: Primary and residual disinfection in potable water, final effluent disinfection in wastewater, cooling water biocide treatment. 

Dosing considerations: Concentration degrades over time (especially sodium hypochlorite). Dose must account for chlorine demand from organic matter. Residual must be maintained through distribution. 

Pump requirements: Chemical-resistant materials (PVDF, ceramic, PTFE), vapor-lock-resistant design, precise residual control with ORP or chlorine analyzer feedback.

Function: Raise or lower pH to optimize treatment processes, protect equipment, and meet discharge requirements. 

Common chemicals - for raising pH: Sodium hydroxide (caustic soda), lime (calcium hydroxide), soda ash (sodium carbonate), sodium bicarbonate. 

Common chemicals - for lowering pH: Sulfuric acid, hydrochloric acid, carbon dioxide. 

Applications: Coagulation pH optimization, biological process protection, distribution system corrosion control, industrial waste neutralization. 

Dosing considerations: Logarithmic pH response requires high turndown ratios and precise control. Lime slurry requires abrasion-resistant equipment and anti-settling design.

Function: Protect piping, equipment, and distribution infrastructure from corrosion and mineral scale deposits.

Common chemicals: Orthophosphates, zinc orthophosphate, polyphosphates, phosphonates, silicates, filming amines.

Applications: Potable water distribution systems, cooling towers, boiler systems, RO membrane protection.

Dosing considerations: Inhibitor concentration must be maintained within a narrow optimal range. 

Pump requirements: High accuracy, stable low-flow capability, chemical compatibility with phosphate and silicate solutions.

Function: Remove residual chlorine from treated wastewater or process water before discharge or sensitive equipment. 

Common chemicals: Sodium bisulfite (NaHSO₃), sodium metabisulfite, sulfur dioxide gas, ascorbic acid, sodium ascorbate. 

Applications: Wastewater effluent dechlorination (NPDES compliance), RO membrane protection, food-grade water treatment.

Function: Prevent or destroy hydrogen sulfide (H₂S) and other odorous compounds in wastewater systems.

Common chemicals: Sodium hypochlorite, hydrogen peroxide, ferric chloride, ferrous sulfate, calcium nitrate, sodium hydroxide.

Applications: Collection system odor control, headworks treatment, sludge handling odor mitigation.

Function: Address specific treatment challenges. 

Examples: Potassium permanganate (KMnO₄) for iron, manganese, and taste/odor control. Powdered activated carbon (PAC) for emergency taste and odor events. Antiscalants for RO membrane pretreatment. Oxygen scavengers for boiler feedwater. Biocides for cooling water treatment.