Treatability studies on optimizing coagulant type and dosage in combined coagulation/membrane processes for table olive processing wastewater

Abstract

A considerable amount of process water has been consumed by table olive industry. As a result of the process, large volumes of table olive process wastewater (TOPW) are released with a high value of chemical oxygen demand (COD), a significant amount of suspended solids (SS) and conductivity. So, the treatment of TOPW becomes more important due to its toxic impacts on the environment and stringent regulations about the discharging. This study aims to investigate the treatability of real TOPW by integrated wastewater treatment technology which was comprised of chemical coagulation/flocculation and membrane processes. In chemical treatment studies, optimum types and dosages of coagulants/flocculants and operating pH were examined. In membrane treatment studies, the supernatant of the coagulated/flocculated wastewater was further treated by advanced membrane filtration technologies which contain ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). UF membrane was used as a pretreatment prior to NF/RO membranes with a 46.7% COD removal efficiency. Then, types of NF/RO membranes and operating pH were optimized. The limit values for discharging standards were provided for both RO membranes which contained COD value lower than 150 mg/L. As a conclusion, an integrated membrane process represents a promising alternative for the treatment of TOPW.