The enhanced biological removal of phosphorus (EBPR) is a popular process due to high removal efficiency, low operational costs, and the possibility of phosphorus recovery. Nevertheless, the stability of the EBPR depends on different factors such as: temperature, pH, and the presence of toxic compounds. While extensive studies have researched the effects of temperature and pH on EBPR systems, little is known about the effects of different toxic compounds on EBPR. For example, sulphide has shown to inhibit different microbial activities in the WWTP, but the knowledge about its effects on EBPR is limited. Whereas the sulphide generated in the sewage can cause a shock effect on EBPR, the continuously exposure to sulphide potentially generated in WWTP can cause the acclimatization and adaptation of the biomass.
This research suggests that sulphate reducing bacteria can proliferate in WWTP, as they are reversibly inhibited by the recirculation of sludge through anaerobic-anoxic-oxic conditions. The research enhances the understanding of the effect of sulphide on the anaerobic-oxic metabolism of PAO. It suggests that the filamentous bacteria Thiothrix caldifontis could play an important role in the biological removal of phosphorus. It questions the ability of PAO to generate energy from nitrate respiration and its use for the anoxic phosphorus uptake. Thus, the results obtained in this research can be used to understand the stability of the EBPR process under anaerobic-anoxic-oxic conditions, especially when exposed to the presence of sulphide.
1.2. Scope of the thesis
1.3. Literature Review
1.4. Problem statement and objectives
1.5. Research approach
2 Effect of electron acceptors on sulphate reduction activity at WWTP
2.4. Material and methods
3 Sulphide effects on the physiology of Candidatus Accumulibacter phosphatis Type I
3.4. Materials and methods
4 Long-term effects of sulphide on the enhanced biological removal of phosphorus: The symbiotic role of Thiothrix caldifontis
4.2. Graphical Abstract
4.4. Materials and methods
5 Cooperation between Competibacter sp. and Accumulibacter in denitrification and phosphate removal processes
5.4. Materials and Methods
6 Absent anoxic activity of PAO I on nitrate under different long-term operational conditions
6.4. Material and methods
7 Outlook and main conclusions
7.1. General conclusions
7.2. Specific conclusions
7.3. Evaluation and outlook
Effect of electron acceptors on sulphate reduction activity at WWTP
Long-term effects of sulphide on the enhanced biological removal of phosphorus: The role of Thiothrix caldifontis
Cooperation between Competibacter sp. and Accumulibacter in denitrification and phosphate removal processes
Absent anoxic activity of PAO I on nitrate under different long-term operational conditions
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.