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Greywater Reuse Treatment Cost Estimator

This estimator calculates the operating cost of treating greywater from fixed periodic expenses, a variable treatment cost per cubic meter, and the treated volume. It provides a simple way to compare operating scenarios or estimate the blended cost of reuse without assuming a particular filtration, biological, or disinfection technology. The result separates fixed cost from variable cost and reports a unit treatment cost. This makes it useful when assessing whether higher system utilization lowers the cost per cubic meter. The model is intentionally transparent: enter cost assumptions that reflect the actual treatment process and local operating conditions. Capital cost, financing, replacement reserves, distribution pumping, and regulatory compliance costs are excluded unless you deliberately include them in the fixed or variable inputs.

Inputs

m³
USD
USD/m³
Result
—
Total treatment cost
Variable cost—
Unit treatment cost—
Fixed-cost share—

1. Enter treated volume
Use the amount of greywater processed during the same period as the fixed cost.

2. Add fixed operating costs
Enter recurring costs that do not scale directly with volume.

3. Enter the variable treatment rate
Use a per-cubic-meter estimate for costs that change with throughput.

4. Check scope consistency
Include comparable cost categories when evaluating multiple treatment options.

5. Review total and unit cost
Use the unit value for scenario comparison, while keeping treatment performance requirements equivalent.

Variable cost = Treated volume × Variable rate Total treatment cost = Fixed operating cost + Variable cost Unit treatment cost = Total treatment cost ÷ Treated volume

When treated volume is zero, unit cost is not defined. This calculation is for the cost scope entered by the user and is not automatically a whole-life system cost.

What the result means

The total is the estimated treatment operating cost for the selected period and throughput.

Use cost inputs based on the actual required water quality and treatment train; different end uses can require different process steps and monitoring.

Given
Treated volume = 95 m³/month; fixed operating cost = $260/month; variable rate = $0.68/m³.

Calculation
Variable cost = 95 × $0.68 = $64.60.
Total treatment cost = $260 + $64.60 = $324.60.
Unit cost = $324.60 ÷ 95 = $3.42/m³.

Result
$324.60 per month

At this volume, fixed costs dominate the blended unit cost; comparing utilization scenarios can show the effect of throughput.

Does the unit cost include collection plumbing?

Only if you include those costs in the entered fixed or variable values. By default the calculator is neutral about which cost categories are included.

Can energy be included in the variable rate?

Yes, when energy use scales reasonably with treated volume. If there is a large constant standby load, you may prefer to include that portion in fixed cost.

How should replacement media be handled?

You can convert expected media replacement expense into a per-volume rate or a periodic fixed allowance, depending on how the replacement schedule is modeled.

Why is unit cost high at low flow?

Fixed costs are spread across fewer cubic meters when throughput is low, which increases the blended cost per cubic meter.

Can this estimate total project economics?

It is one component. A project-level analysis can also include capital cost, distribution energy, backup water, sewer effects, maintenance reserves, and any applicable fees or incentives.