The physical chemistry of pH — the dissociation of water, the carbonate buffer system, alkalinity and titration curves — that determines reagent demand and how difficult a stream is to control.
Water self-ionises with Kw = 10−14 at 25°C, fixing the neutral point at pH 7 and linking hydrogen- and hydroxide-ion activity.
pH measures hydrogen-ion activity, which diverges from concentration in saline and high-ionic-strength waters — relevant to produced water and brine.
Kw and electrode response vary with temperature, so accurate control requires temperature compensation.
Alkalinity — principally bicarbonate and carbonate — is the acid-neutralising capacity that resists pH change and sets reagent demand.
The CO2–bicarbonate–carbonate equilibria govern buffering across the pH range and couple pH control to scaling risk.
Buffer intensity peaks near each pKa (about 6.3 and 10.3 for the carbonate system) and is minimal at the equivalence points.
Titrating a stream with acid or base and plotting pH against reagent dose reveals everything a designer needs: the total reagent demand to reach the target, the buffered regions where dosing is forgiving, and the steep equivalence zone where overshoot occurs. The slope dpH/dC is the inverse of buffer intensity; control systems are tuned to this slope, which is why a measured titration curve is requested for any difficult or strongly buffered stream.
The curve fixes the stoichiometric and practical reagent demand, sizing storage and dosing.
A steep curve means a hard control problem requiring staging and tight loop tuning.
Carbonate equilibria flag where pH change will precipitate scale, informing reagent choice.
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.
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