Aroma characterization of raw and electrochemically treated goat whey wastewater

Whey wastewater is considered to be the main polluting product of the dairy industry. Electrocoagulation (EC) and electrooxidation (EO) processes using aluminum electrodes and inactive boron-doped diamond (BDD), respectively, were applied to reduce the chemical oxygen demand (COD), total nitrogen (TN), phosphate (PO₄^-3), nitrate (NO₃^-), chloride (Cl^-), total phenolic compounds (TPCs), and optical density. In parallel, thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) with HiSorb passive sorption extraction probe was employed to monitor the emitted volatile organic compounds (VOCs) from the electrochemical treatments. A total of 35 VOCs were extracted and identified in the raw whey wastewater, while 27 and 53 VOCs were identified in the EC and EO treated whey wastewater, respectively. EO-treatment was more concerning as chlorinated VOCs were detected showing a total presence of 50%. Two trichloromethanes (THMs), methane bromodichloro and trichloromethane, as well as ethane 1,2-dichloro, and propane 1,2-dichloro were quantified and their mean concentrations were 5.0, 125.2, 15.1, and 6.4 ppb_v, respectively. Overall, the aroma profile remained mostly unaffected by the EC-treatment. Also, COD, TN, Cl^-, NO₃^-, PO₄^-3, TPCs, and optical density presented a reduction of 7.4, 52.5, 11.9, 27, 16.8, 54.8, and 17.3% with EC. On the contrary, EO was only effective for COD and optical density, with removal of 14.3, and 23.5%, respectively, while all the other concentrations of pollutants increased (TN, Cl^-, NO₃^-, PO₄^-3, TPCs).