Mass balance and process simulation for water management in mineral processing

Water is everywhere in a processing plant. It carries solids, hosts chemical reactions and leaves the site in products, tailings and effluents. Managing it well requires one thing first: figures you can trust. USIM PAC builds a consistent plant water balance from measured data, then uses it to simulate water use and recycling scenarios. A paper presented at the SIM 2026 French Congress of the mineral Industries Society, in Chalons en Champagne (France).

Why water management matters in mineral processing

Processes cannot run without water. Water carries the ore from one stage to the next, and it is the medium where flotation, leaching and reagent reactions take place.

Water demand follows a simple chain. As ore grades fall, plants treat more tonnes of ore to produce the same metal. More tonnes means more water.To limit fresh water intake, plants recycle their process water. Recycling has an effect on process performance. Dissolved species and residual reagents build up, and flotation results can change.

Three types of constraints weigh on the plant:

Water balance frameworks

A water balance is required at several levels, each with its own framework. Scope, level of detail and frequency differ from one level to the next. All these frameworks share one thing: they rest on a mass balance.

From mass balance to water balance

Water accounting is the systematic tracking of all water entering, circulating in and leaving a site. It covers quantity and quality. It is the basis for reporting, optimisation and dialogue with stakeholders.

A mass balance is what makes water accounting reliable. It is used for reporting, but above all for running the plant, since it gives a consistent view of all flows. At each node of the flowsheet, inputs equal outputs plus any change in stock. This is true for solids, for each mineral, for each element, and for water.

Raw plant data never close the balance. Data reconciliation corrects each measurement within its uncertainty, and the least reliable measurements are corrected the most. It also estimates the flows that are not measured. You end up with one consistent set of flows.

To note: CASPEO’s reconciliation algorithm is available in BILCO and in USIM PAC software.

The same process applies to water. However water balances raise difficulties that solids balances rarely meet. The paper explores why with a real plant case.

Neverthless, for a site-wide water reporting, a quantitative balance on a simplified flowsheet is enough. A balance on a detailed flowsheet needs more assumptions, this is where simulation takes over.

USIM PAC process simulation software
Water management flowsheet ITERAMS project

Modelling water in a process simulation software

A simulator handles water on four fronts:

• Solid/liquid separation models control water quantities
• Water treatment models control water quality
• The circuit tracks how water quality changes from stage to stage
• Process models link water quality to process performance.

The last point is the hardest. It answers the question plants ask most: what happens to recovery if we recycle more water? This point will be presented through two simulation studies: the first one with a long loop where process water is treated before it returns to the plant, the second one, a short loop, where water goes straight back after solid/liquid separation.

Mass balance and process simulation; what the tools bring

The mass balance gives the observed state. Simulation explores new configurations.

Used together, they:

• Gather plant data and make them usable
• Give a solid base to monitor operations
• Open up optimisation opportunities
• Improve risk management, for stocks and for planned changes in operating conditions

CASPEO at the SIM 2026 congress

Etienne Braak will present CASPEO’s methods and tools for water accounting and simulation at the SIM 2026. The SIM congress 2026,  the annual congress-exhibition of the Société de l’Industrie Minérale, the French mineral industry society, is dedicated to water: “Water: essential resource and strategic issues”. It takes place from 6 to 9 October 2026 at Le Capitole, Châlons-en-Champagne.

Etienne’s paper is titled “Assessment and Simulation: Tools for Integrated Water Management in the Mining Industry”. The presentation will show how a mass balance builds robust water accounting and makes published consumption figures reliable, and how It also calibrates simulators to test recycling and effluent treatment scenarios, instead of costly plant trials. The lecture will present implementation challenges and results from research case studies.