Fenton-like application to pretreated cheese whey wastewater

•The Fenton-like process as a post-treatment of cheese whey wastewater is reported.•An organic matter reduction of 80% was achieved for the precoagulated wastewater.•Precipitation, biodegradation and Fenton process allowed a COD removal close to 100%.•Iron removal from the oxidation stage was carried out by Ca(OH)2 addition.•The generated sludge presented zone sedimentation and a high settling rate.

Cheese whey wastewater has been treated by the Fenton-like oxidation system after being pre-processed through a coagulation – flocculation stage with FeCl3 or alternatively, through a sedimentation step with Ca(OH)2 plus aerobic digestion. In the first case, Fenton-like oxidation is capable of reducing the initial COD (chemical oxygen demand) to 80% of the initial value, 20% of COD shows recalcitrance to chemical oxidation regardless of the operating conditions used. In the second case, the oxidation system is capable of removing almost the total COD present in the pretreated effluent. Given the lower values of initial COD, complete COD conversion is achieved at short reaction times within minutes depending on the initial reagent concentration. Removal of Fe(III) from the oxidation treatment can be achieved by Ca(OH)2 addition. Sedimentation pH significantly affects the observed settling rate. Hence, neutral conditions lead to better results than slightly acidic pHs.

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