Management of sour cherry processing industry wastewater by super critical fluid method: Sequential recovery and treatment

The fruit processing industry wastewater contains a significant amount of bioactive substances. In the sustainability framework and the circular economy, the by-product can be transformed into valuable resources before being treated. By integrating management strategies, the industry can minimize its environmental footprint, promote economic benefits, and support the sustainability of freshwater resources. This study subjected consecutively recovery (supercritical CO2: SC-CO2) and treatment (supercritical water oxidation: SCWO) by using the supercritical fluid method. In this study, sour cherry UF retentate with high-load organics, which include especially valuable phenolics was used. The mean COD and total phenolic substance content (TPC) were determined as 15,650 mg/L and 457 mg GAE/L, respectively. Recovery efficiencies of TPC and total flavonoid substance content (TFC) of extracts were up to 5 % and 10 % with SC-CO2 extraction, respectively. Additionally, the highest enrichment efficiencies were determined as 35 % and 140 %. While the TPC of sour cherry UF retentate was 72 mg/100 g sample, it increased up to 278 mg/100 g in the extract obtained under 40 °C and 30 MPa. Flavonoids from phenolic substances had high recoverability in SC-CO2 compared to the other phenolic groups. Following extraction, the samples were treated using the supercritical water oxidation process. Wastewater with high organic load was effectively treated in a short time (15 min) and the removal efficiencies changed between 78 % and 98 %. Additionally, toxicity tests were conducted in selected optimum extraction (27 MPa and 40 °C) and oxidation (1.68 DOD and 3 min) conditions, and the toxicity units of extracted and treated wastewaters decreased compared to those obtained from raw wastewater for Daphnia magna and Vibrio fischeri toxicity tests. These findings show that the supercritical fluid method can be a favorable alternative for management of fruit juice industry wastewater.