Chemical dosing is the controlled addition of a reagent to a water or wastewater stream at the right concentration, at the right point, at the right time. Get it right and you hit consent at minimum chemical cost; get it wrong and you over-dose (waste, residual toxicity, downstream upsets) or under-dose (consent failures). This is the complete engineering reference: the equations, the stoichiometry, process design, control strategy, mixing and injection, and how to diagnose dosing faults.
Four variables decide whether a dose works.
Every dosing duty is the same four-part problem: how much reagent (the dose, set by stoichiometry or jar testing), where it goes in (the injection point and mixing), how it is paced (the control loop), and how it is confirmed (the analyser and mass balance). Each of those has its own page below. Master the four together and dosing becomes predictable and cheap; treat any one casually and the chemical bill, the consent risk and the maintenance load all climb.
Set by reaction stoichiometry, charge demand or a jar-tested target, expressed as mg/L of active chemical and converted to a delivered mass or volume flow.
Dosing equationsThe reagent must be dispersed into the bulk flow fast enough to react uniformly — the right quill, the right rapid-mix energy, the right contact time.
Mixing & injectionFlow-paced, residual-trim or compound-loop control keeps the dose on target as flow and influent quality change through the day.
Dose-rate controlA representative analyser and a closed mass balance prove the dose is actually being delivered and consumed as designed.
Process designThe reagent you choose fixes most of the lifetime cost, sludge and safety before a pump is sized — weigh active cost, by-products and handling together.
Dosing strategyCompliant storage, bunding and containment keep the reagent usable and the site safe — the part that turns a dosing rig into a dosing system.
Storage & containmentEight in-depth references behind this hub — equations, process, strategy and fault-finding.
The core formulae: mg/L ↔ kg/day ↔ pump stroke, neat vs diluted solution, flow-paced dose and worked examples.
Read MoreAcid/alkali neutralisation, coagulant charge demand, metals precipitation and disinfection — how to calculate the chemical a reaction actually needs.
Read MoreFeed-forward (flow-paced), feedback (PID) and compound-loop maths, dead-time, and how to size a control range.
Read MoreFrom mass balance to P&ID: storage, transfer, injection point, mixing, contact tank, bunding and the full design sequence.
Read MoreReagent selection, single vs multi-point dosing, set-point strategy, and trimming chemical cost without risking consent.
Read MoreRapid-mix G-value, injection quills and diffusers, in-line static mixers, and getting reagent dispersed before it reacts.
Read MoreSymptoms, causes and fixes for chemical over-dosing — residual toxicity, pH overshoot, sludge volume, cost blow-out.
Read MoreWhy a pump that “looks” fine still under-delivers — vapour lock, valve fouling, gassing, calibration drift.
Read MoreThe chemicals most often dosed in industrial water and wastewater — each links to its dedicated page.
Ferric, alum and PAC dosing for charge neutralisation — flow-paced with turbidity trim. Dose set by jar test and charge demand.
Polymer make-up and dosing for bridging flocculation, clarification and dewatering. Ageing, dilution and gentle mixing matter.
Acid and caustic/lime dosing for pH correction and neutralisation — the most non-linear, fastest dosing loop on most sites.
Chlorine, hypochlorite and related oxidants dosed to a residual or CT target with ORP/residual control.
Hydroxide and sulphide precipitation of heavy metals — dose driven by stoichiometry and solubility minima.
Packaged dosing skids, tanks, pumps and instrumentation for any of the above duties.
From bulk store to injection point — what every dosing installation contains.
The pump sets the achievable accuracy and turndown. See dosing pump selection and the metering-pump types: diaphragm, peristaltic and progressive-cavity.
Loop design lives on the dosing control strategy page; documentation on P&ID services and SCADA integration.
Run the numbers with the chemical dosing calculator and check stoichiometry on the reagent-demand page.
We don't sell pumps off a shelf — we engineer and build complete dosing systems and skids. These pages cover that service.
The full design-and-build service — scope, engineer, build, commission.
Read MoreSkid-mounted, factory-tested, fully automated dosing units.
Read MoreTurning a duty into a pump, tank and material specification.
Read MoreInstrumentation, PLC, control panel and SCADA integration.
Read MoreTanks, bunding, material compatibility and chemical safety.
Read MoreCoordinated, automated systems dosing several reagents or points.
Read MoreAcid and alkali dosing for neutralisation — the headline application of chemical dosing.
Read MoreFeedback, feed-forward and cascade control modes and PID tuning.
Read MoreSize a dose rate and pump setting from flow, dose and solution strength.
Read MoreThe process context for coagulant and polymer dosing.
Read MoreTell us the duty — flow range, target dose or consent, reagent and stream chemistry — and we will size the pumps and storage, specify the injection and mixing, design the control loop and document the P&ID. Existing installation over- or under-dosing? We audit and fix.
Our expertise spans multiple industries with sector-specific water treatment solutions.