Precise neutralisation and pH control for process water and effluent — from strongly buffered alkaline and acidic streams to fine potable trimming — engineered around the titration chemistry and the consented pH band.
pH spans 14 orders of magnitude and small reagent errors cause large swings
pH is the negative logarithm of hydrogen-ion activity, so each unit is a ten-fold change; near neutrality a tiny reagent excess moves pH sharply.
Alkalinity and weak-acid systems buffer the water, so reagent demand depends on the whole titration curve, not a single set-point.
Poorly controlled dosing overshoots into the opposite regime and can precipitate scale as carbonate equilibria shift.
The shape of the titration curve dictates reagent type, staging and control
Most natural waters are buffered by the carbonate system; bicarbonate and carbonate equilibria set alkalinity and resistance to pH change.
Buffer capacity (the reagent needed per unit pH change) peaks near the system pKa and collapses at the equivalence point, where pH moves fastest.
Strong-acid/strong-base neutralisation gives a sharp endpoint; weak systems give a gradual curve that is easier to control but needs more reagent.
The reagent required to shift pH is governed by the buffer intensity β = dCb/d(pH), the moles of acid or base per litre needed per unit pH change. β is highest where the water is well buffered (near a pKa) and lowest at the equivalence point, where pH changes almost discontinuously. This is why a single feedforward dose rarely works: control must follow the local slope of the titration curve, dosing aggressively through the buffered region and gently through the steep equivalence zone.
Reagent and staging chosen to match the buffering and the safety case
Carbon dioxide forms carbonic acid and is inherently self-limiting near neutral pH — the safest route for alkaline correction with no acidic overshoot risk.
Sulphuric or hydrochloric acid and caustic or lime give fast, precise correction where space or reaction time is limited.
Staged reaction tanks with feedback pH control prevent overshoot and hold a stable discharge through the steep equivalence zone.
In-depth scientific guides to the chemistry, systems and compliance of pH control
pH, the dissociation of water, alkalinity, buffer capacity and titration curves — the chemistry that determines reagent demand and control difficulty.
View GuideAcids, alkalis and CO2 compared, multi-stage neutralisation, mixing and feedback control for stable, overshoot-free correction.
View GuideThe 6–9 discharge band, continuous pH monitoring, control reliability and evidencing compliant operation.
View GuidepH is among the most closely monitored discharge parameters
Most consents require discharge pH within roughly 6 to 9; sustained excursions are a reportable breach.
Redundant inline pH instrumentation with alarms and logging evidences continuous compliance.
Duty/standby dosing and reaction-tank buffering protect compliance through load swings and upsets.
Reynolds & Bauhm designs pH-adjustment and neutralisation systems — from self-limiting CO2 carbonation to multi-stage acid/alkali control — matched to your buffering chemistry and discharge consent.
Our expertise spans multiple industries with sector-specific water treatment solutions.