An innovative device to convert olive mill wastewater into a suitable effluent for feeding purple non-sulfur photosynthetic bacteria

A device (prototype) with a working volume of 200 L was used to deplete olive mill wastewater (OMW) of polyphenols. The OMW transformed into feedstock by means of the device was then used for feeding a lab-scale photobioreactor, just for testing the production of bioH2. The main novelty of this prototype consists in the combination of several adsorbent matrices and the exploitation of their synergic action. In this investigation, three matrices have been used: active carbon, Azolla and zeolite. The device was operated at an olive oil company located in the heart of the Chianti zone (Province of Florence, Italy). The efficiency of polyphenol removal obtained using the device was >=96%. The multi-matrix effluent (MMeff) generated was then used to obtain three different culture broths containing 25%, 50% and 100% of MMeff, respectively. The diluted (with water) culture broths were suitable for hydrogen generation, with the highest hydrogen production rate (12.7 mL H2/Lculture/h) being obtained using 50% MMeff. The hydrogen yields were: 334 mL H2/L of MMeff, when feeding the photofermenter with pure effluent (100%); 1308 mL H2/L of MMeff, with the half-diluted effluent (50%, v/v); and 432 mL H2/L of MMeff, with the highest-diluted effluent (25%, v/v).