The Enhanced Biological Phosphorus Removal (EBPR) process is a biological process for efficient phosphate removal from wastewaters through intracellular storage of polyphosphate by Phosphate-Accumulating Organisms (PAO) and subsequent removal through wastage of excess sludge. Although many studies have demonstrated the existence of different PAO clades, the functional differences among these clades and potential implications for the process performance remained unclear. Furthermore, the salinity effects on the EBPR process had not been properly investigated, which is necessary to assess its applicability for the treatment of saline wastewaters.
The first part of the thesis focuses on the functional diversity among PAO clades. It demonstrates significant functional differences in the main characteristics of the anaerobic metabolism of two different PAO clades and provides fundamental insight in the metabolic response of PAO to different influent P/C ratios. In addition, it shows how these functional differences provide competitive advantages to specific PAO clades in a selection study and discusses their potential implications on process performance, in particular for combined biological and chemical systems for nutrient removal and recovery.
The second part of the thesis describes the salinity effects on the metabolism of PAO and their competitors that do not contribute to phosphorus removal; the so-called Glycogen-Accumulating Organisms (GAO). It shows how salinity affects the different metabolic processes (kinetics and stochiometry) of PAO and GAO and provides a model that describes the salinity effects on their kinetic rates. Finally, it discusses the potential implications of sudden saline shocks in wastewater treatment systems that are not regularly exposed to salinity.
1 GENERAL INTRODUCTION
1.2 ENHANCED BIOLOGICAL PHOSPHATE REMOVAL (EBPR)
1.2.1 PAO METABOLISM
1.3 FACTORS AFFECTING THE EBPR PROCESS PERFORMANCE
1.4 SALINITY AS A FACTOR AFFECTING MICROORGANISMS
1.5 SCOPE OF THESIS
2 ACCUMULIBACTER CLADES TYPE I AND II PERFORMING KINETICALLY DIFFERENT GLYCOGENACCUMULATING ORGANISMS METABOLISMS FOR ANAEROBIC SUBSTRATE UPTAKE
2.2 MATERIAL AND METHODS
2.8 APPENDIX 2A
2.9 SUPPLEMENTARY DATA
3 METABOLIC RESPONSE OF 'CANDIDATUS ACCUMULIBACTER PHOSPHATIS' CLADE II TO CHANGES IN THE INFLUENT P/C RATIO
3.2 MATERIAL AND METHODS
3.8 APPENDIX 3A, DETAILED DESCRIPTION OF EQUATIONS FOR POLY-P ESTIMATION
4 PREVALENCE OF 'CANDIDATUS ACCUMULIBACTER PHOSPHATIS' CLADE II UNDER PHOSPHATE LIMITING CONDITIONS
4.2 MATERIAL AND METHODS
5 DENITRIFICATION PATHWAYS OF PAO CLADE I WITH DIFFERENT CARBON SOURCES
5.2 MATERIAL AND METHODS
6 IMPACT OF SALINITY ON THE ANAEROBIC METABOLISM OF POLYPHOSPHATE-ACCUMULATING ORGANISMS (PAO) AND GLYCOGEN-ACCUMULATING ORGANISMS (GAO)
6.2 MATERIAL AND METHODS
6.8 APPENDIX 6A
6.9 APPENDIX 6B.
6.10 APPENDIX 6C.
7 IMPACT OF SALINITY ON THE AEROBIC METABOLISM OF POLYPHOSPHATE-ACCUMULATING ORGANISMS
7.2 MATERIAL AND METHODS
7.8 APPENDIX 7A
7.9 APPENDIX 7B
8 GENERAL CONCLUSIONS AND OUTLOOK
8.1 METABOLIC FLEXIBILITY AND FUNCTIONAL DIVERSITY AMONG ACCUMULIBACTER CLADES
8.2 SALINITY EFFECTS ON PAO AND GAO
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.