Raw water does not arrive at a treatment works in one unchanging condition. A useful dosing decision starts by understanding what is entering the process now, rather than relying on an assumption based on yesterday’s conditions.
For drinking-water turbidity removal, Compass uses incoming-water measurements in a site-specific feed-forward relationship. The purpose is to predict coagulant demand as the source water changes. The measurements, model and plant interface are established for the particular works.
Start with the incoming signal
Online optical and turbidity information can show a change in the water before that change has passed through treatment. A plant team needs to know where each measurement is taken, which units are used and whether the record is representative of the water reaching coagulation.
A trend is most useful alongside operating records and laboratory evidence. Align timestamps and note changes in sampling, cleaning or instrument configuration before interpreting a rise or fall as a change in source-water quality.
Turn measurement into a prediction
The Compass feed-forward model relates the agreed incoming measurements to the coagulant demand of that works. Its output is a calculated dose for the defined turbidity-removal duty. It is a site-specific control approach, so a chart from one location is not a performance promise for another.
Compass EOR addresses a different drinking-water objective: enhanced organics removal. It adds an agreed treated-water optical measurement that can trim the incoming-water prediction through feedback. The extra measurement belongs to that EOR configuration; it is not a feature to assume for every Compass installation.
See the decision in context
A useful operator view should put the incoming signal, calculated dose and relevant process trend on a common time axis. Clear units, reference methods and alarm or operating limits help the team understand what the model is responding to. The colourful examples on this site are illustrative interface concepts, not measured plant readings.
Before proposing a configuration, PMA reviews the treatment objective, available data, applicable instrumentation generation and existing dosing arrangement with the site team. Older Compass material describes s::can equipment; the May 2025 instrumentation pack specifies TriOS OPUS and LISA UV for its stated configuration. The applicable hardware is confirmed for each project.
What to bring to the discussion
- The source-water variability and the turbidity or organics-removal objective.
- Available online measurements, sample locations, units and historic trends.
- The current coagulant, dosing strategy and plant control interface.
- Laboratory reference data and any known seasonal or operational changes.
Those details make the first conversation more useful. PMA can then review whether Compass or Compass EOR is the appropriate starting point for the duty. For the published application overview, see PMA’s drinking-water coagulation control page.
