Settling sludge after Fenton oxidation
Fenton treatment breaks down stubborn COD in pharma effluent, then leaves iron sludge behind. Here is how polymer finishes the job.
What Fenton does
Ferrous iron and hydrogen peroxide react in acid conditions to form hydroxyl radicals, which break hard-to-treat organics into simpler compounds the biological stage can handle.
The usual sequence
Acidify (around pH 3 is the commonly reported optimum), add ferrous sulphate, dose peroxide gradually, then neutralise with lime or caustic soda, which precipitates the iron.
Why polymer is needed
The iron precipitate is fine and slow to settle. A flocculant gathers it into heavy flocs so the water can move on clean.
Which charge
Iron hydroxide sludge is mineral, so an anionic grade is the usual starting point: Anionic HQ or Anionic MQ. Compare a cationic grade in the jar test if organics remain high.
Find the dose by trial
Peroxide, iron and polymer doses all depend on the effluent. Bench-test the whole sequence before changing the plant.
Related
Polyelectrolyte dosing guide
Starting doses, solution strength and how to work out kilograms per day.
Read →Where this work clusters
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