Optimization of the Electron Donor Supply to Sulphate Reducing Bioreactors Treating Inorganic Wastewater

The main objective of this research was to optimize the electron donor supply in sulphate reducing bioreactors treating sulphate rich wastewater. Two types of electron donor were tested: lactate and slow release electron donors such as carbohydrate based polymers and lignocellulosic biowastes. Biological sulphate reduction was evaluated in different bioreactor configurations: the inverse fluidized bed, sequencing batch and batch reactors. The reactors were tested under steady-state, high-rate and transient-state feeding conditions of electron donor and acceptor, respectively. The results showed that the inverse fluidized bed reactor configuration is robust and resilient to transient and high-rate feeding conditions at a hydraulic retention time as low as 0.125 d. The biological sulphate reduction was limited by the COD:sulphate ratio (< 1.7). The results from artificial neural network modelling showed that the influent sulphate concentrations synergistically affected the COD removal efficiency and the sulphide production. Concerning the role of electron donors, the slow release electron donors allowed a biological sulphate reduction > 82% either using carbohydrate based polymers or lignocellulosic bio-wastes, in batch bioreactors. The biological sulphate reduction was limited by the hydrolysis-fermentation rate and by the complexity of the slow release electron donors.

Luis Carlos Reyes-Alvarado (born in Cordoba, Veracruz, Mexico) obtained his PhD in Environmental Technology. He joined the Universidad Veracruzana (Mexico) where he obtained the degree of Chemical Engineering and further a Master in Food Science and Technology, after which he received an ALFA grant within the SUPPORT (Sustainable Use of Photosynthesis Products & Optimum Resource Transformation) project at the TU Graz (Austria).
Luis developed and defended his PhD thesis through the Erasmus Mundus Joint Doctorate Programme in Environmental Technologies for Contaminated Solids, Soils and Sediments (ETeCoS³) on December 16^th, 2016. His research was focused on the optimization of electron donor supply to sulphate reducing bioreactors treating inorganic wastewater rich in sulphate and carried out at different institutions: the UNESCO-IHE (Delft, The Netherlands), the Universidad Veracruzana (Veracruz, Mexico), the INRA-Laboratoire de Biotechnologie de l’Environnement (Narbonne, France) and the University of Cassino and Southern Lazio (Cassino, Italy). Luis' main interest is understanding the engineering aspects of biological processes, resource recovery from waste and the development of eco-technologies for waste remediation.