Assessing the applicability of a new carob waste-derived powdered activated carbon to control pharmaceutical compounds in wastewater treatment

• Published in: The Science of the total environment Vol. 743; p. 140791
• Main Authors: Viegas, Rui M.C., Mestre, Ana S., Mesquita, Elsa, Campinas, Margarida, Andrade, Marta A., Carvalho, Ana P., Rosa, Maria João
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.11.2020
• Subjects: Adsorption; Modelling; Pharmaceutical compounds; Steam activation; Waste-derived activated carbons; Waste-derived activated carbons; Modelling; Adsorption; Pharmaceutical compounds; Steam activation
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.140791

This paper assesses the applicability of a new carob waste-derived powdered activated carbon (PAC) obtained by steam activation for pharmaceutical compounds (PhCs) removal in urban wastewater treatment plants (WWTPs) with activated sludge (AS) secondary treatment. The new carob-derived PAC presents chemical and textural properties similar to a high-performing commercial PAC produced from vegetable source by physical activation. The adsorption isotherms of three target PhCs, carbamazepine, diclofenac and sulfamethoxazole, spiked (at around 100 μg/L) in mixed liquor (ML) and in clarified-ML from the AS-bioreactor of a WWTP show: (i) minor reduction of PAC capacity with real MLs compared to clarified MLs; (ii) the higher the PhC hydrophobicity, the higher the PAC adsorption capacity in both water matrices; (iii) hydrophobic interactions probably overweight electrostatic interactions between the PhCs and the slightly positively charged PAC in these real water matrices with background organics and inorganics. The PhC adsorption results with ML and clarified-ML are used to calibrate the IAST-based tracer model (TRM) and predict the new PAC performance when added to AS-bioreactor vs. in post-secondary treatment, at the PhC naturally-occurring trace concentrations. The modelling projections show (i) one needs higher PAC doses than those reported in the literature, particularly in post-treatment, and (ii) the benefits of PAC dosing to the bioreactor, with only a slightly higher PAC dose being needed when compared to its post-secondary dosing and minimising the capital investment. [Display omitted] •Steam activation of carob processing waste allows obtaining micro-mesopore PAC.•Carob-PAC has similar capacity to PhCs in mixed liquor and clarified mixed liquor.•The higher PhC hydrophobicity, the higher PAC adsorption capacity in both waters.•The results and modelling approach may allow predicting the PAC full-scale dosing.•PAC dosing to bioreactor seems more advantageous than in post-treatment.