Enhancing a multi-stage process for olive oil mill wastewater valorization towards polyhydroxyalkanoates and biogas production

Most of OMW soluble chemical oxygen demand (COD) content in the liquid fraction (approximately 70%) was removed in a sequencing batch reactor (SBR) obtaining a high PHA production (about 532 mgCOD, in the feast phase). In particular, the strategy to uncouple COD feed from nitrogen supply within the SBR cycle, along with the operation of a settling phase before the famine phase, allowed to enhance the selective pressure towards PHA-storing microorganisms. Polymer production significantly increased in the accumulation reactor up to approximately 2470 mgCOD/L. Finally, anaerobic digestion tests on the OMW solid fraction showed a relevant COD conversion into methane (up to 100%).