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.
Chapter 1 - Introduction
1.2 The PhD thesis structure
Chapter 2 - Literature review
2.1 Anaerobic digestion
2.2 The sulphate reduction process
2.3 Electron donors for SRB
2.4 Conventional bioreactors for sulphate reduction
2.5 Modelling biological sulphate reduction
Chapter 3 - Forecasting the effect on feast and famine conditions on biological sulphate reduction in an anaerobic inverse fluidized bed reactor using artificial neural networks
3.2 Material and methods
Chapter 4 - High rate biological sulphate reduction in a lactate fed inverse fluidized bed reactor at a hydraulic retention time of 3 H
4.2 Material and methods
Chapter 5 - Effect of the initial sulphate concentration on the start-up phase of the biological sulphate reduction in sequencing batch reactors
5.2 Material and methods
Chapter 6 - The effect of nitrogen and electron donor feastfamine conditions on biological sulphate reduction in inorganic wastewater treatment
6.2 Material and methods
Chapter 7 - The effect of feast and famie conditions on biological sulphate reduction in anaerobic sequencing batch reactors
7.2 Material and methods
Chapter 8 - Carbohydrate based polymeric materials as slow release electron donors for sulphate removal from wastewater
8.2 Material and methods
Chapter 9 - Lignocellulosic biowastes as carrier material and slow release electron donor for sulphidogenesis of wastewater in an inverse fluidized bed bioreactor
9.2 Material and methods
Chapter 10 - General discussion and perspectives
10.2 General discussion and conclusions
10.3 Future research work
IHE Delft PhD programme leads to a deepening of a field of specialisation. PhD fellows do scientific research, often with conclusions that directly influence their region. At IHE Delft, PhD researchers from around the world participate in problem-focused and solution-oriented research on development issues, resulting in an inspiring research environment. PhD fellows work together with other researchers from many countries dealing with topics related to water and the environment.
PhD research is often carried out in the ‘sandwich’ model. Preparation and final reporting – the first and last portion of the programme – are carried out in Delft, while actual research is done in the fellow’s home country, under co-supervision of a local institute. Regular contacts with the promotor are maintained through visits and long-distance communication. This enables researchers to employ solutions directly to problems in their geographical region.
IHE Delft PhD degrees are awarded jointly with a university. The degrees are highly valued and fully recognised in all parts of the world.