Water recovery from pistachio processing plant wastewater using subcritical water oxidation method

Abstract This study aims to apply an efficient and environmentally friendly subcritical water oxidation (SWO) method for the treatment of pistachio processing plant wastewater (PPPW). The effects of temperature (336.2–399.8 K), the concentration of H2O2 (0.08–0.92 M) and treatment time (6.4–73.6 min) on the oxidation of PPPW were investigated using the SWO method and experimental parameters were optimized using the response surface method. While the highest chemical oxygen demand (COD) removal was obtained as 53.8% in 73.6 min at 373 K using 0.5 M of H2O2, the highest obtained total phenol (TP) and color removals were 92.80%, and 99.6%, respectively, in 20 min at 373 K using 0.75 M of H2O2. R 2 values of COD, TP and color removal models were 0.9694, 0.9868 and 0.9649, respectively, and F values of the models were 35.24, 82.86 and 30.54, in the same order. In the vast majority of the experimental samples, the concentrations of nitrate, total phosphate, total nitrogen and suspended solids were found to be decreased while the nitrite concentration was increased after the SWO process. The effectiveness of SWO in water recovery from PPPW was demonstrated by the high, COD, TP and color removal values obtained. Graphical Abstract