Concept One of the major environmental problem in Mediterranean countries is the safe disposal of olive mill wastewater (OMW) derived from the extraction process of olive oil. The organic load of OMW is within the 50-150 g/L range and includes organic compounds as sugars and polyphenols [1]. Polyphenols, more soluble in the water than oil, have concentrations ranging from 0.5 to 25 g/L in OMW [2]. Studies on OMW valorization have proved that biorefinery integrated concepts can effectively bio-convert OMW to a group of desired products as reported by [3]. The olive oil mill can produce very different waste types, depending on the extraction system operated: discontinuous and continuous. This last is, substantially, a 2-phase system or 3-phase system. The production of olive oil through 3-phase extraction system, leads to the co-production of large quantities of olive mill wastewater and a separate solid waste named olive husk. Motivations and Objectives Agro-industrial wastewaters are a potential no-cost feedstock for feeding bioprocesses; among wastewaters can be found OMWs. Although OMWs are nutrient-rich for feeding bioprocesses, they are complex to be degraded because of: low pH; dark color; high BOD and COD contents and significant amounts of polyphenols (phytotoxic substances). This last are also a potential antioxidant sources, consequently, integrated technologies should be developed in order to maximize the valorization of OMW. Since pure OMWs have not been proved suitable as feedstock, a pretreatment is needed for polyphenol removal before their use. The phenol-free OMWs (e.g. by sorption) are also a low-cost feedstock for feeding photosynthetic processes in order to produce biofuels (hydrogen and lipids) and or bioplastics as polyhydroxyalkanoates (PHAs). Results and Discussion The chemical, physical, biological, and combined treatment technologies of OMW have been examined aiming at efficient and feasible processes [3]. A few researcher groups investigated on OMW dephenolization by sorption. Several adsorbent matrices have been proposed for polyphenol removal from OMW: a granular active carbon (GAC); an aquatic dry-fern named Azolla (Az); a zeolite (Z) and a non-polar resin (Amberlite, XAD16). A solid phase extraction procedure dedicated to the recovery of polyphenols from OMWs has been investigated [4]. Diluted OMW have been used for feeding bioreactors growing heterotrophic bacteria (fermentation), purple non-sulfur photosynthetic bacteria (photofermentation), phototrophic microorganisms as microalgae and/or cyanobacteria (mixotrofic growth conditions). A two-stage process, e.g. dark fermentation followed by photofermentation, has also been carried out. Since 2010, our group has investigated on bioH2 production feeding photobioreactors with dephenolized OMW. These last can be used fresh or stored: fresh-OMW are rich in sugars, while stored-OMW are rich in volatile fatty acids (VFAs).
Treated OMW for feeding photosynthetic processes in order to produce green products
Carlozzi P;Padovani G
2015
Abstract
Concept One of the major environmental problem in Mediterranean countries is the safe disposal of olive mill wastewater (OMW) derived from the extraction process of olive oil. The organic load of OMW is within the 50-150 g/L range and includes organic compounds as sugars and polyphenols [1]. Polyphenols, more soluble in the water than oil, have concentrations ranging from 0.5 to 25 g/L in OMW [2]. Studies on OMW valorization have proved that biorefinery integrated concepts can effectively bio-convert OMW to a group of desired products as reported by [3]. The olive oil mill can produce very different waste types, depending on the extraction system operated: discontinuous and continuous. This last is, substantially, a 2-phase system or 3-phase system. The production of olive oil through 3-phase extraction system, leads to the co-production of large quantities of olive mill wastewater and a separate solid waste named olive husk. Motivations and Objectives Agro-industrial wastewaters are a potential no-cost feedstock for feeding bioprocesses; among wastewaters can be found OMWs. Although OMWs are nutrient-rich for feeding bioprocesses, they are complex to be degraded because of: low pH; dark color; high BOD and COD contents and significant amounts of polyphenols (phytotoxic substances). This last are also a potential antioxidant sources, consequently, integrated technologies should be developed in order to maximize the valorization of OMW. Since pure OMWs have not been proved suitable as feedstock, a pretreatment is needed for polyphenol removal before their use. The phenol-free OMWs (e.g. by sorption) are also a low-cost feedstock for feeding photosynthetic processes in order to produce biofuels (hydrogen and lipids) and or bioplastics as polyhydroxyalkanoates (PHAs). Results and Discussion The chemical, physical, biological, and combined treatment technologies of OMW have been examined aiming at efficient and feasible processes [3]. A few researcher groups investigated on OMW dephenolization by sorption. Several adsorbent matrices have been proposed for polyphenol removal from OMW: a granular active carbon (GAC); an aquatic dry-fern named Azolla (Az); a zeolite (Z) and a non-polar resin (Amberlite, XAD16). A solid phase extraction procedure dedicated to the recovery of polyphenols from OMWs has been investigated [4]. Diluted OMW have been used for feeding bioreactors growing heterotrophic bacteria (fermentation), purple non-sulfur photosynthetic bacteria (photofermentation), phototrophic microorganisms as microalgae and/or cyanobacteria (mixotrofic growth conditions). A two-stage process, e.g. dark fermentation followed by photofermentation, has also been carried out. Since 2010, our group has investigated on bioH2 production feeding photobioreactors with dephenolized OMW. These last can be used fresh or stored: fresh-OMW are rich in sugars, while stored-OMW are rich in volatile fatty acids (VFAs).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
