Olive Mill Wastewater (OMW) Polyphenols Adsorption onto Polymeric Resins: Part I—Batch Anaerobic Digestion of OMW

Abstract

Adsorption experiments using pure aqueous phenol solutions (in the range of 200 to 1000 ppm) were performed in the presence of different adsorbent resins (namely XAD 4, XAD 16, FPX 66) at 1% w/v (ratio of resin weight to phenol solution volume) at constant temperature (25 °C) and ionic strength (0.1 M NaCl). Langmuir and Freundlich isotherm models were used to describe the adsorption kinetics of all tested resins. The experimental equilibrium data were very well fitted to both Langmuir and Freundlich models (R2 > 0.900). FPX 66 exhibited the best efficiency among the tested resins. Regeneration of adsorbent resins thus recovery experiments of pure phenol solutions were also performed. Adsorbent tested resins were further examined in different mass ratios (10, 15, 20%) for phenolics removal from olive mill wastewater (OMW). A reduction of 75% of the soluble phenolic content was observed when 20% of FPX 66 was applied. Finally batch anaerobic digestion experiments of resin-pretreated OMW were carried out under mesophilic conditions (37 °C). Augmentation of methane production was measured during anaerobic digestion of resin-pretreated OMW compared to raw OMW. Polyphenols in OMW were proved to inhibit OMW fermentation and thus methane production.