Treatment of fruit processing wastewater by advanced oxidation processes

In this thesis, characterization of the ultrafiltration retentate in apple, cherry, orange and pomegranate concentrated fruit juice production (respectively EKA, VKA, PKA and NKA) was carried out in terms of conventional parameters. Also, their treatability studies using Fenton oxidation (FO), ozone oxidation (OO) and supercritical water oxidation (SCWO) as advanced oxidation methods (AOPs) were carried out. Lowest and highest chemical oxygen demand (COD) concentration in raw wastewaters were found as 13284 mg/L and 172800 mg/L for NKA and EKA, respectively. BOD/COD ratios for NKA, PKA, VKA and EKA were detected as 0.6, 0.6, 0.5 ve 0.39, respectively. In the treatability studies carried out by FO, the COD concentrations of EKA, VKA, PKA, NKA were removed as 99%, 92%, 71% and 99%, respectively, at the H2O2/Fe2+ ratios of 30-50 and above the stoichiometric oxidant dosage (DOD > 1). Total phenolic content (TPC) and color were also removed 99%. It was determined that TPC increased by 6 times while the DOD value and the H2O2/Fe2+ ratio were below or close to 1 in FO process. In the treatment of EKA, VKA, PKA and NKA by ozonation; it was determined that the color removal was quite high (88% - 99%) while the COD removal efficiency was between 13% and 77%. It was observed that the TPC value increased depending on the ozonation time of wastewaters. In SCWO, removal efficiencies of COD, TPM, total solid content (SS) and color for all wastewaters were higher than 94%, 99%, 90% and 98%, respectively, at the high DOD (DOD > 1) and short reaction time (2.9 min). It was concluded that FO and SCWO processes were more advantageous than OO in terms of COD, TPM and SS removal efficiencies. However, OO can compare to these two oxidation methods in color removal. Cost analysis was calculated using chemical and electricity consumptions for the optimum operating conditions in terms of COD removal efficiency. FO have lower operation cost for VKA and NKA with relatively low pollutant concentration while OO has lower operation cost for EKA and PKA.