PFAS GAC Changeout Scheduler

Forecast when a granular activated carbon vessel treating PFAS-laden water will hit breakthrough so you can time changeouts and budget media costs.

Total PFAS concentration entering the GAC vessel in parts per trillion.
Regulatory or client PFAS limit after treatment in parts per trillion.
Time water resides in the GAC bed; longer EBCT increases adsorption capacity.
Average daily throughput through the lead vessel in gallons.
Leave blank to assume $5.00 per cubic foot of carbon media (purchase only).

Engineering planning tool only — confirm changeout schedules with column testing and regulatory requirements.

Examples

  • 120 ppt influent, 4 ppt target, 12-minute EBCT, 180,000 gal/day ⇒ Changeout in 8.39 months (~255 days) with ~$1,003 media cost.
  • 45 ppt influent, 2 ppt target, 10-minute EBCT, 65,000 gal/day ⇒ Changeout in 14.03 months (~427 days) with ~$302 media cost.

FAQ

How should I incorporate lead-lag vessels?

Run the calculator for the lead vessel to establish breakthrough timing, then stagger the lag changeout based on your sampling lag and swap policy.

Does temperature or competing contaminants affect the result?

Yes — colder water and co-contaminants reduce adsorption capacity. Use conservative inputs and validate against pilot data when available.

Can I budget disposal costs here?

Use the media cost field to include disposal or regeneration fees by raising the per-cubic-foot value accordingly.

How often should I validate this schedule with sampling?

Verify breakthrough assumptions with regular effluent sampling; adjust EBCT or flow inputs as soon as lead vessel data shows PFAS creep toward the target limit.

Additional Information

  • Formula scales changeout days with EBCT, influent-to-effluent ratio, and daily flow raised to a 0.784 power to reflect contact time sensitivity.
  • Bed volume is derived from EBCT and flow (EBCT minutes × flow ÷ 1,440) and converted to cubic feet for cost estimation.
  • Media cost defaults to $5 per cubic foot; adjust for vendor quotes, freight, or disposal uplifts.
  • Changeout interval reflects the lead vessel; run again with lag vessel assumptions to plan staggered replacements.

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