No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Enhanced biological phosphorus removal (EBPR) is a biological wastewater treatment process facilitated by polyphosphate-accumulating organisms (PAO). The absence of isolates that have the PAO phenotype has limited the scope of studies into the physiology of these industrially significant and metabolically unique organisms. This thesis outlines findings into the physiology and ecology of EBPR in mixed microbial cultures, which contribute to the fundamental understanding of the process. The first experimental approach used in these studies was to investigate the microbial abundance of identified PAOs and GAOs in full-scale and lab-scale EBPR processes, and correlate these data with chemical monitoring methods both at a “macroscale” and “microscale”. The “macroscale” studies consisted of process optimisation experiments that found propionate to be a more effective and stable carbon source than acetate. The “microscale” study investigated the activity of Competibacter, growing in dense aggregates. This study discovered that the structure of the granules affected the distribution of activity by limiting the supply of oxygen and that the activity of the Competibacter in turn affected the structure of the aggregate. The second experimental approach was to target key facets of the microbial physiology of PAOs and GAOs at a molecular level. Environmental gene expression studies were used to investigate the stimulus for the expression of a putative Accumulibacter polyphosphate kinase gene (ppk). This study found that the expression of this gene was repressed by high external phosphate concentrations, which suggests that the pho regulon is functioning in Accumulibacter. In another study, previously published models were integrated and elaborated to develop a model for the membrane transport processes in PAOs and GAOs, which give them the unique ability to sequester VFA without an electron acceptor. These studies confirmed that the proton-motive force (PMF) drives the uptake of VFA by both PAOs and GAOs and postulated fundamental differences in the molecular mechanisms that PAOs and GAOs use to create a PMF in the absence of respiratory electron transport. The studies also explain the molecular basis for findings in other studies that PAOs have a competitive advantage over GAOs at increased pH. The third experimental approach was to attempt to isolate organisms significant to EBPR. Some measure of success was achieved: colonies of Competibacter were obtained in pure culture but the growth could not be sustained further than the growth of micro-colonies just visible to the eye. EBPR microbiology, like many other subjects of inquiry in environmental microbiology, has benefited greatly from developments in molecular methods to identify and describe microbial communities. However, the investigation of microbial physiology in the environment remains a challenge; this thesis has taken up that challenge. Discoveries regarding the benefits of propionate as a carbon source and the basis for the competitive advantage that PAOs derive from an increased pH have potential application for practitioners of EBPR plants. Furthermore the findings make a contribution to the fundamental understanding of the physiology of EBPR organisms that may in the future lead to entirely novel approaches to EBPR optimisation.

High-rate anaerobic degradation of soluble organic pollutants is becoming very popular, particularly for carbohydrate-based industrial wastewaters. Despite the successes achieved, there are significant limitations in the application of this technology to more complex wastewaters. These are defined as containing other organic compounds such as particulate and soluble proteins and fats, and originate from abattoirs (slaughterhouses), meat and food processing and similar industries. Complex wastewater is often difficult to degrade and components such as solids and fats have slow degradation kinetics and can diminish process performance. Also, the growth of granular sludge, which is critical for optimal performance in upflow reactors, is slow and granule properties such as shear strength and settling velocity are poorer. This is reflected in a lower treatment efficiency of 50%-60% in systems treating complex wastewater compared with efficiencies of 85%-95% in carbohydrate fed treatment systems. This thesis examines specific aspects in the treatment of complex (proteinaceous) wastewater in high rate upflow anaerobic treatment plants and the influences of different conversion processes and microbial characteristics on design and operation. The research problem was approached in two ways: The macroscopic conversion processes were examined by investigating and modelling a two-stage full-scale high rate hybrid reactor in Spearwood, Western Australia, designed and operated by ESI Ltd. This allowed localisation of the key conversion process; specifically hydrolysis of solids, which was found to occur mainly within the methanogenic reactor. Degradation of soluble proteins was rapid and all proteins were fully acidified in the acidogenic (first) stage even at very low retention times. Because of the rapid protein degradation rates, partial acidification, which is often a strategy to improve granulation rates, is incompatible with pH, flow and concentration equalisation. The influence of a protein feed on granulation compared with a carbohydrate feed was examined by sampling granules from the above reactor, as well as two full scale brewery fed reactors and a full scale reactor fed fruit and vegetable cannery wastewater. The cannery fed granules had the highest shear strength and settling characteristics while the protein fed granules had low strength and density , low settling velocity and a comparatively wide size distribution. Both brewery fed granules had very similar and suitable properties. Molecular studies using fluorescent in-situ hybridisation (FISH) probing and microscopy indicated that the granules from the complex (protein) wastewater fed reactor had limited structural characteristics , possibly due to limited reaction rates (as opposed to diffusion rates). Granules from the cannery reactor and both brewery reactors had structures that appeared to be the result of diffusion limitations. Therefore, the critical operational constraints when treating complex wastewater are the particulate biomass and particulate substrate. Awareness of process status could be increased by monitoring of biological and substrate solid inventory in the methanogenic reactor. The model developed in this thesis can greatly assist this. Complications due to particulate substrate and poor granule properties may be intrinsic to complex feeds. These constraints are probably best addressed by design of a methanogenic reactor specifically for complex wastewater. The design should attempt to separate substrate hydrolysis, minimise shear on the granules and retain solids.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.