Fenton” reactor is one of the processes of advanced chemical oxidation, applied to oxidize the organic complex constituents, hardly degradable by biological way, transforming them into final simpler products.
This technology is based on the high reactivity of the hydroxyl radical, which is created from hydrogen peroxide and iron, under controlled conditions of pH and temperature.
In particular, adding hydrogen peroxide (H2O2) at 35% and ferrous sulfate (FeSO4) ) in acid condition (pH 2,5 –3), maintained by the dosing of sulfuric acid, hydroxyl radicals OH° are produced according to the following formula: H2O2 + Fe++ → Fe+++ + OH- + OH°
The radical OH°,reacting in aqueous solution with the major part of aliphatic and aromatic molecules, involvs the rupture of C-C links and then, due to chain mechanisms, the degradation of the contaminants. For this reaction, it is required a retention time of about two hours.
In a second tank, also this provided with slow electro-agitator, hydrated lime or soda are added to neutralize the discharges and to eliminate the excess of H2O2, adjusting the pH through reagents’ dosage and a pH-meter. For this second phase, it is required a retention time of about an hour and a half.
Fenton reactor also needs a third step, the flocculation tank, where, through the dosage of polyelectrolyte, it accelerates the separation of sludge flocks from the treated water. The flocculation tank must ensure a contact time of at least 15 minutes.
AAt the exit of the oxidative FENTON treatment, the water must be sent to a sedimentation tank to separate the clarified water from the settled sludge. In this phase, the sludge reaches a thickening of 1÷2%, so it is necessary also to provide a sludge thickening tank, to reach an higher density of sludges.
The advantages of this technology are:
- Destruction of organic compounds
- Reduction of the toxicity
- Best biodegradability of complex compounds
- Removing the color and smells
The disadvantages are:
- An increase in operating costs for the purchase of chimica regents;
- An increased danger in handling/ storage of reagents;
- UAn high production of toxic sludge, difficult to dispose;
- A significant increase of dissolved salts (TDS).