Resource recovery and safe discharge of food wastewater based on membrane treatment technology: a case of mixed processing wastewater from potato and sweet potato

Abstract

The mixed processing wastewater of potato and sweet potato is classified as high-concentration organic wastewater. If this wastewater is discharged directly into natural waters, it will cause severe pollution. Furthermore, the valuable components in the wastewater are difficult to recycle, resulting in great waste. Consequently, this study implemented two wastewater treatment systems, designated TS1 and TS2, which employ membrane technology. In the TS1 system, chemical oxygen demand (COD) reduced by 82.10 % and biological oxygen demand (BOD₅) by 90.96 %. Approximately 50 % of polysaccharides and all of proteins were retained, thus enabling the recycling of water resources. The TS2 system was designed to ensure that the treated wastewater will comply with the requisite discharge standards. The process parameters of the system were optimized, and the operating pressure of 30 kD and 150 D was set to 0.25 MPa. The operating pressure of 10, 5 and 1 kD membranes was set to 0.3 MPa, while the inlet temperature of the mixed wastewater was set at 27 °C. The operational cycle of the 30 kD, 5 kD and 150 D ultrafiltration membranes was 30 min. The working time of the 10 kD ultrafiltration membrane was 35 min. The working time of the 1 kD ultrafiltration membrane was 20 min. A wastewater treatment system was developed that, by modifying the system parameters, can treat wastewater produced by a range of fruits and vegetables. Furthermore, an assessment of the method's feasibility was conducted. The energy consumption ranged from 0.37 to 0.86 kWh/m³, and an acid-base alternating cleaning-in-place (CIP) protocol was employed. This system presents an innovative approach to the treatment of wastewater from fruits and vegetables.