Effect of clay pretreatment on photofermentative hydrogen production from olive mill wastewater

The aim of this paper was to gain further insight into the effect of the clay pretreatment process oil photofermentative hydrogen production. This two-stage process involved a clay pretreatment step followed by photofermentation. which was performed under anaerobic conditions with the illumination by Tungsten lamps. Rhodobacter sphaeroUts O.U.001 was used for photofermentation. Higher amounts of color (65%), total phenol (81%) and chemical oxygen demand (3%) removal efficiencies were achieved after clay pretreatment process. During photofermentative hydrogen production with the effluent of clay pretreatment process, the main organic compounds resulting higher hydrogen production rates were found to be acetic, lactic, propionic, and butyric acids. Compared to photofermentation using raw olive mill wastewater (16 L-H2/L-OMW), the amount of photofermentative hydrogen production was doubled by using the effluent of the clay pretreatment process (31.5 L-H2/L-OMW). The reasons for the improvement of hydrogen production by clay treatment call be attributed to the high removal of the hardly biodegradable compounds such as phenols; minor removal of organic acids, sugars and amino acids that are known to enhance photofermentative hydrogen production; and the color depletion of raw OMW which might cause a shadowing effect on the photosynthetic bacteria

Comparison of physicochemical characteristics and photofermentative hydrogen production potential of wastewaters produced from different olive oil mills in Western-Anatolia, Turkey

Olive oil extraction produces a dark-colored wastewater that contains nutrients that can be further processed using biotechnology, in parallel with treatment for disposal. For instance, olive mill wastewater (OMW) can be used as a substrate for photofermentative hydrogen production by purple bacteria. A comparative study was investigated with several OMW samples front different olive oil mills in Western-Anatolia, Turkey. The composition of OMW varies significantly for each mill; thus, a detailed physicochemical analysis of each sample has been carried out. Subsequently, samples were assessed for their functioning in anaerobic photofermentative hydrogen production by Rhodobacter sphaeroides O.U.001. The highest hydrogen production potential (19.9 m(3) m(-3)) was obtained by the OMW sample with the highest organic content (mainly acetic acid, 9.71 kg m(-3)) and the highest carbon-to-nitrogen (C/N) molar ratio (73.8 M M(-1)). The organic content was found to be composed of primarily acetic, aspartic, and glutamic acids. There was a linear relationship between C/N ratio and hydrogen production potential across the different OMW samples. This study is unique due to the wide range of analyses of OMW samples and the comparison of many parameters for hydrogen production from wastewater. The results obtained throughout this study can aid in the design of systems using wastewater for biohydrogen production. Particularly, the C/N ratio was found to be the best parameter for choosing a proper substrate

Hydrogen production by Rhodobacter sphaeroides OU001 in a flat plate solar bioreactor

Rhodobacter sphaeroides O.U.001 can produce hydrogen under anaerobic conditions and illumination. The objective of this study was to investigate the performance of an 81 flat plate solar bioreactor operating in outdoor conditions. Different organic acids were used as carbon sources (malate, lactate and acetate) and olive mill waste water was used as a sole substrate source. The consumption and the production of the organic acids were determined by HPLC. The accumulation of by-products, such as poly-beta-hydroxybutyrate (PHB) and carotenoid, throughout the course of hydrogen production was determined

Biological hydrogen production from olive mill wastewater with two-stage processes

In the present work two novel two-stage hydrogen production processes from olive mill wastewater (OMW) have been introduced. The first two-stage process involved dark-fermentation followed by a photofermentation process. Dark-fermentation by activated sludge cultures and photofermentation by Rhodobacter sphaeroides O.U.001 were both performed in 55 ml glass vessels, under anaerobic conditions. In some cases of dark-fermentation, activated sludge was initially acclimatized to the OMW to provide the adaptation of microorganisms to the extreme conditions of OMW. The highest hydrogen production potential obtained was 291H(2)/l(OMW) after photofermentation with 50% (v/v) effluent of dark fermentation with activated sludge. Photofermentation with 50% (v/v) effluent of dark fermentation with acclimated activated sludge had the highest hydrogen production rate (0.00811(-1) h(-1))

Design of an outdoor stacked - tubular reactor for biological hydrogen production

Photofermentation is one alternative to produce hydrogen sustainably. The photobioreactor design is of crucial importance for an economically feasible operation, and an optimal design should provide uniform velocity and light distribution, low pressure drop, low gas permeability and efficient gas-liquid separation. A glass, stacked tubular bioreactor aimed at satisfying these criteria has been designed for outdoor photofermentative hydrogen production by purple non sulfur bacteria. The design consists of 4 stacked U-tubes (tube diameter 3 cm) and 2 vertical manifolds. The hydrodynamics of the 3-dimensional model of this reactor was solved via COMSOL Multiphysics 4.1. The effects of tube length (1.4, 2.0, 3.8 m), tube pitch (8, 10.5, 13 cm) and volumetric flow rate (25-250 L/h) on the flow distribution were investigated. The glass stacked tubular reactor design results in less ground area and longer life time. This design has been constructed and operated with using Rhodobacter capsulatus YO3 hup(-) and molasses as the carbon source under outdoor conditions. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

A compact tubular photobioreactor for outdoor hydrogen production from molasses

Hydrogen can be produced sustainably by photofermentation of biomass. For an economically feasible operation, the process should be implemented outdoors using low-cost organic material. In the current study, molasses from a sugar factory was utilized for photofermentative hydrogen production. The experiment was run with Rhodobacter capsulatus YO3 (hup-) in fed-batch mode under outdoor conditions in Ankara between July 12, 2015 and July 24, 2015. The stacked U-tube photobioreactor (9 L) designed for outdoor photobiological hydrogen production by our group was used. The design consists of 4 stacked U-tubes and 2 vertical manifolds. During the operation, the sucrose concentration in the reactor was adjusted to 5 mM daily by diluting the molasses. Maintaining pH at the desired level (around 7.0) was the main challenge of the operation. The pH value was eventually stabilized at 5.9 and hydrogen production was sustained for 8 days with continuous feeding of molasses. The maximum productivity was found as 0.31 mol H-2/(m(3) h). In this study, a long term photobiological hydrogen production from molasses under outdoor conditions was demonstrated for the first time. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Improvement of carbon dioxide tolerance of PEMFC electrocatalyst by using microwave irradiation technique

The microwave irradiation technique was used to prepare platinum and platinum-ruthenium-based electrocatalysts on Vulcan for PEMFCs. The effects of microwave duration, base concentration and surfactant/precursor ratios on the properties of Pt-based catalysts were investigated. The prepared Pt-based catalysts were characterized by XRD and then PEMFC tests were performed. The particle sizes of the catalysts were ranging between 2 and 6 nm. Platinum-ruthenium-based catalysts were prepared to improve the carbon dioxide tolerance of the PEMFCs. The power losses arising from carbon dioxide in hydrogen feed were decreased by using the prepared PtRu-based catalysts when 30% carbon dioxide including hydrogen was sent to the fuel cell. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved