Pilot-scale treatment cycle comprising membrane, thermal, and adsorption processes for spent metalworking fluids remediation

BACKGROUND: Spent metalworking fluids (SMWFs) represent a process waste characterized by low biodegradability, high toxicity, and very heterogeneous contamination typology connoted by the occurrence of numerous different pollutants. In this regard, the development of technically flexible and efficient treatment systems is fundamental to prevent sanitary and environmental risks deriving from SMWF disposal. RESULTS: A treatment cycle including ultrafiltration (UF), evaporation, reverse osmosis (RO), and granular activated carbon (GAC) adsorption was tested at pilot scale for the remediation of three real SMWFs. A total of 44 parameters (physical, chemical, and ecotoxicological), identifying the SMWF characteristics and contamination, were analyzed after each treatment unit. The treatment cycle performance was investigated with and without the UF phase. In the complete cycle, UF was effective for the decrease of (average values) total suspended solids (96%), total hydrocarbons (> 99%), animal fats and oils (> 99%), and ecotoxicity (85%). In the same cycle, the evaporation significantly reduced the organic content (91% on average), and RO followed by GAC adsorption further provided effluents suitable for reuse in industrial applications. For the cycle without UF, parameters such as chemical oxygen demand, biochemical oxygen demand, and ecotoxicity showed values still significant (on average equal to 5550 mg L-1, 1933 mg L-1, and 95%, respectively) after evaporation. However, RO and GAC adsorption units allowed the achievement of effluents suitable for discharge in sewer systems. CONCLUSIONS: According to the results, this work provides treatment strategies displaying high SMWF remediation efficiency and wide adaptability over various requirements for the achievement of specific effluent quality standards.(c) 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).