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Water & process arithmetic

Flow-Weighted Concentration Calculator

Calculate a nonreactive combined concentration from up to three matched stream flows and constituent concentrations. See each stream’s contribution to the total mass rate.

116 / COMBINE MATCHED STREAM DATA

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Starting values are illustrative. Use your own costs, rates and assumptions.

INPUT GROUP 01

Stream A

Use the same constituent and concentration basis in every stream.

INPUT GROUP 02

Stream B

Use the same constituent and concentration basis in every stream.

INPUT GROUP 03

Stream C

Use the same constituent and concentration basis in every stream.

Check the assumptions before acting on a result.

Read the method and example

YOUR CALCULATION

A nonreactive flow-weighted concentration on a common volume basis.

Combined flow (m³/h)

30

Flow-weighted concentration (mg/L)

100

Combined constituent mass rate (kg/h)

3

Constituent contribution by stream

Constituent contribution by stream
StreamFlow (m³/h)Concentration (mg/L)Constituent load (kg/h)
Stream A20501
Stream B102002
Stream C000

Keep the calculation

Saving is optional and stays on this device. Unsaved edits are not kept when you leave. CSV includes every input and the current results.

Illustrative inputs loaded. Replace them with your own assumptions.

How the flow-weighted concentration calculator works

Combined concentration = sum of (flow × concentration) divided by the sum of flows. The volume basis is m³/h and every concentration is in mg/L for the same constituent. The table shows each stream separately; stream labels are fixed and no identifying details are needed.

Constituent mass rate in kg/h = flow in m³/h × concentration in mg/L × 0.001. This follows from 1,000 L per cubic meter and 1,000,000 mg per kilogram. The combined mass rate is the sum of the individual constituent rates. All zero flows produce zero mass rate and an unavailable combined concentration.

The model assumes conserved constituent mass, additive liquid volume and matching conditions. It does not simulate reactions, settling, adsorption, evaporation or density changes. Do not use this arithmetic to average pH, determine chemical preparation quantities, set an operating dose or establish discharge compliance.

Worked example

Stream A at 20 m³/h and 50 mg/L contributes 1 kg/h. Stream B at 10 m³/h and 200 mg/L contributes 2 kg/h. With stream C at zero flow, the total is 30 m³/h and 3 kg/h, giving 100 mg/L. Changing B to 20 m³/h gives 40 m³/h, 5 kg/h and 125 mg/L.

Sources and assumptions

The source material explains the underlying calculation or pricing structure. Entered prices, costs, schedules and scenario choices are your assumptions; this tool does not obtain supplier quotes or predict actual results.

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