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.
1 Introduction 2 Literature review 3 Forecasting the effect of feast and famine conditions on biological sulphate reduction in an anaerobic inverse fluidized bed reactor using artificial neural networks 4 High rate biological sulphate reduction in a lactate fed inverse fluidized bed reactor at a hydraulic retention time of 3 h 5 Effect of the initial sulphate concentration on the start-up phase of the biological sulphate reduction in sequencing batch reactors 6 The effect of nitrogen and electron donor feast-famine conditions on biological sulphate reduction in inorganic wastewater treatment 7 The effect of feast and famine conditions on biological sulphate reduction in anaerobic sequencing batch reactors 8 Carbohydrate based polymeric materials as slow release electron donors for sulphate removal from wastewater 9 Lignocellulosic biowastes as carrier material and slow release electron donor for sulphidogenesis of wastewater in an inverse fluidized bed bioreactor 10 General discussion and perspectives
Sewage - Purification - Biological treatment, Metal wastes - Environmental aspects, TECHNOLOGY & ENGINEERING / Environmental / General, Water supply & treatment, Hydrology & the hydrosphere