A wastewater pH control system measures the pH of washdown and cleaning water and doses acid or alkali automatically to bring it within an acceptable range before it leaves the site. Food and beverage plants are particularly exposed: clean-in-place (CIP) systems and washdowns use strong caustic and acid solutions, and the resulting wastewater can swing from very high to very low pH within a single cleaning cycle.
What uncontrolled pH costs
Without automatic control, the consequences fall into three groups:
- Trade waste exceedances. Utilities set acceptable pH ranges for trade waste. Urban Utilities’ trade waste acceptance criteria, for example, specify a pH range of 6 to 10.5. Discharges outside the approved range can lead to compliance action and additional costs.
- Damage to pipes and pits. Strong acid and caustic flows attack concrete pits, pipe joints and metal fittings on site.
- Manual dosing. Staff add chemicals by hand based on spot checks, which is inconsistent and exposes them to hazardous chemicals more often than necessary.
Why washdown pH is hard to control
Cleaning schedules release chemicals in pulses. A caustic wash followed by a rinse, then an acid wash, produces a sequence of high, neutral and low pH flows that arrive at the drain within minutes of each other. pH is also logarithmic: each unit of pH represents a tenfold change in concentration, so the amount of acid or alkali needed to correct a flow changes sharply near neutral. Manual dosing cannot respond to changes on that timescale, and simple on/off dosing tends to overshoot.
How a wastewater pH control system works
Wastewater collects in a mixing tank, where pH is measured continuously and corrected by metered dosing before discharge.
How it works
- 1
Collect and mix
Washdown water flows into a mixing tank, where a mixer or recirculation pump blends it to a uniform pH.
- 2
Measure
pH probes in the tank and at the discharge measure continuously, with automatic cleaning where the wastewater is fatty.
- 3
Dose
Metering pumps add acid or alkali in proportion to the deviation from setpoint, slowing as pH approaches range to avoid overshoot.
- 4
Release and record
Water is released when pH is within range. pH, doses and discharge times are logged for your records.
One contract, every trade licensed
A pH control system includes plumbing and drainage connected to the sewer. We carry out the electrical, instrumentation and controls work under QLD Electrical Contractor Licence 1513082. Tanks, pipework and sewer connections are installed by a QBCC-licensed plumbing contractor that we engage and manage. You deal with one contract and one accountable lead.
pH is one part of trade waste quality. Plants that also need to manage flow, load and charges should see trade waste compliance.
The commercial case
The benefit combines reduced compliance risk, less chemical use through measured dosing, and reduced wear on drainage infrastructure. Chemical savings are the easiest to estimate.
Alternatives
- Manual dosing. Low cost, but inconsistent and dependent on staff availability and chemical handling.
- Changing cleaning chemicals. Worth reviewing with your chemical supplier, but cleaning still produces pH swings.
- Packaged treatment units. A practical choice for some sites. Integration with your drainage, cleaning schedules and records is where a site-specific design adds value.
- Separate trades. Engaging an electrician, plumber and controls contractor separately leaves coordination and accountability with the site.