title: Thermal pretreatment of olive mill wastewater for efficient methane production: control of aromatic substances degradation by monitoring cyclohexane carboxylic acid.
abstract: Anaerobic digestion is investigated as a sustainable depurative strategy of olive oil mill wastewater (OOMW). The effect of thermal pretreatment on the anaerobic biodegradation of aromatic compounds present in (OMWW) was investigated. The anaerobic degradation of phenolic compounds, well known to be the main concern related to this kind of effluents, was monitored in batch anaerobic tests at a laboratory scale on samples pretreated at mild (80±1 °C), intermediate (90±1 °C) and high temperature (120±1 °C). The obtained results showed an increase of 34% in specific methane production (SMP) for OMWW treated at the lowest temperature and a decrease of 18% for treatment at the highest temperature. These results were related to the different decomposition pathways of the lignocellulosic compounds obtained in the tested conditions. The decomposition pathway was determined by measuring the concentrations of volatile organic acids, phenols, and chemical oxygen demand (COD) versus time. Cyclohexane carboxylic acid (CHCA) production was identified in all the tests with a maximum concentration of around 200 µmol L(-1) in accordance with the phenols degradation, suggesting that anaerobic digestion of aromatic compounds follows the benzoyl-CoA pathway. Accurate monitoring of this compound was proposed as the key element to control the process evolution. The total phenols (TP) and total COD removals were, with SMP, the highest (TP 62.7%-COD 63.2%) at 80 °C and lowest (TP 44.9%-COD 32.2%) at 120 °C. In all cases, thermal pretreatment was able to enhance the TP removal ability (up to 42% increase).
authors.affiliation: a Department of Civil, Architectural and Environmental Engineering , University of Naples Federico II , Via Claudio, 21, Naples 80125 , Italy.
authors.forename: Ludovico
authors.initials: L
authors.lastname: Pontoni
authors.forename: Giuseppe
authors.initials: G
authors.lastname: d'Antonio
authors.forename: Giovanni
authors.initials: G
authors.lastname: Esposito
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Fabbricino
authors.forename: Luigi
authors.initials: L
authors.lastname: Frunzo
authors.forename: Francesco
authors.initials: F
authors.lastname: Pirozzi
mesh_terms: D000383:Agriculture / Q000379:methods; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D001673:Biodegradation, Environmental; D003509:Cyclohexanecarboxylic Acids / Q000032:analysis / Q000378:metabolism; D005246:Feedback; D025461:Feedback, Physiological / Q000502:physiology; D006361:Heating / Q000379:methods*; D006841:Hydrocarbons, Aromatic / Q000737:chemistry / Q000302:isolation & purification*; D007220:Industrial Waste / Q000517:prevention & control; D008697:Methane / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000069463:Olive Oil; D010938:Plant Oils / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D062065:Wastewater / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical; D018508:Water Purification / Q000379:methods
chemical_list: D003509:Cyclohexanecarboxylic Acids; D006841:Hydrocarbons, Aromatic; D007220:Industrial Waste; D008697:Methane; D000069463:Olive Oil; D010938:Plant Oils; D062065:Wastewater; D014874:Water Pollutants, Chemical; C044895:cyclohexanecarboxylic acid
keywords: HS-SPME-GC-MS; OOMW management; anaerobic digestion; benzoyl-CoA pathway; thermal treatment