ENGINEERING EXPLAINED / FOREVER
Where does the fluorine go?
Move beyond the filter: follow the PFAS, explore thermal-treatment conditions, and close a PFOA fluorine balance.
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01 / SEPARATION
The filter moves it.
Activated carbon, ion exchange and reverse osmosis separate PFAS from water. The fluorine remains in spent media, regenerant or concentrate. Removal from the water is not destruction of the molecule.
PFAS accumulates on the carbon; spent media needs further management.
The reel's 20% concentrate is an example at 80% water recovery, not a universal membrane value. With ideal PFAS rejection, concentrate concentration would be about five times feed concentration. Real recovery and rejection depend on the membrane and feed.
02 / THERMAL TREATMENT
Temperature is one input.
This is a qualitative teaching illustration, not PFAS kinetics or an emissions prediction. It reports no destruction efficiency. The reel's opening “does not burn” is shorthand for resistance to ordinary treatment: PFAS can be destroyed under appropriate, demonstrated conditions.
EPA's 2026 interim guidance discusses thermal treatment under certain conditions and the uncertainty around incomplete-combustion products. Temperature, residence time, mixing, oxygen, feed and pollution controls all matter. Passing 1,100°C alone does not establish complete mineralisation. Verify performance with appropriate measurement and a fluorine balance.
03 / ACCOUNT FOR FLUORINE
One kilogram of PFOA.
mHF,eq = mPFOA × 15 × 20.006 / 414.07
PFOA is C₈HF₁₅O₂. Complete conversion of its 15 fluorine atoms to HF gives about 0.725 kg HF equivalent per kilogram of pure PFOA. This is stoichiometry, not a measured kiln yield. Actual fluorine can leave as HF, inorganic fluoride salts, unreacted PFAS or other fluorinated products. A wet scrubber may neutralise HF into dissolved fluoride salts.
The reel's “every kilogram” applies to the PFOA example. Different PFAS, salts and waste mixtures have different fluorine fractions. A scrubber design also needs the gas flow, composition, contact performance, neutralising reagent and wastewater plan.
- EPA: 2026 interim destruction and disposal guidance.
- EPA: drinking-water separation technologies.
- EPA: thermal-treatment evidence database. The mass balance above is calculated from the PFOA molecular formula and molar masses.