Contact with cement, shotcrete and grout drives construction water to pH 11 to 13. Discharging it untreated is both a consent breach and an environmental hazard; reliable, well-controlled neutralisation is essential.
Specialised water treatment for TBM slurry, groundwater and construction runoff on underground projects.
Dissolved air flotation for oil, grease and fine-solids removal from equipment washdown water.
Screw and belt presses producing stackable cake from excavated spoil and treatment sludge.
This page covers neutralising concrete-contact water — shotcrete, grout and bleed water at pH 12–13 — using self-limiting CO₂ or controlled acid dosing. We highlight it because high-pH water is the most common single cause of discharge non-compliance on a tunnel site. Staged CO₂ sparging is inherently self-limiting — it cannot overshoot below neutral — which makes it safer and simpler to control than mineral-acid dosing, and it adds no chloride or sulphate to the discharge. The plant is sized for the alkaline load of the grouting and shotcrete programme, with pH trim and monitoring proving every batch is within the 6–9 consent window before release.
Fresh cementitious contact water routinely reaches pH 12 to 13, far outside the typical 6 to 9 discharge band.
Dissolved hydroxide and lime resist pH change, so dosing must be controlled carefully to avoid overshoot into acidic territory.
Calcium carbonate precipitates as pH falls, generating solids and scale the system must manage.
Carbon dioxide forms carbonic acid in water and is inherently self-limiting near neutral pH, making it the safest reagent for unattended sites.
Where space or reaction time is limited, controlled sulphuric or hydrochloric acid dosing provides fast, precise correction.
Staged dosing with feedback pH control across reaction tanks prevents overshoot and holds the discharge within consent.
Gas injection skids with diffusers and pH feedback for safe, self-regulating neutralisation.
Mixed reaction vessels with metering pumps and instrumentation for buffered streams.
Redundant pH instrumentation with alarms and data logging to evidence compliant discharge.
Reynolds & Bauhm designs and deploys treatment and recovery packages matched to your geology, programme and discharge consent.
Our expertise spans multiple industries with sector-specific water treatment solutions.