Microbial and biochemical properties of the biological excess phosphate removal process

The reasearch objectives of this thesis are to determine the behavior of specific cellular components in sludge, in response to varying environmental conditions, and determine the role of the glyoxylate cycle in anaerobic PHA storage. These objectives were addressed by idnetifying assays to determine the immediate biochemical state of the sludge biomass and applying these assay to determine typical sludge behavior then.testing a proposed biochemical model. Radioactive labelling of cells showed aerobic phosphate uptake results in storage of two major polyphosphate types, long chain granular or long chain soluble polyphosphates, that can account for up to 85 % of newly synthesized intracellular phosphate-containing compounds. Both of the polyphosphate types were greater than eight ortho-phosphate units long and susceptible to acid hydrolysis. Anaerobically, long chain soluble polyphosphates are degraded and released during polyhydroxyalkanoate (PHA) storage. PHA storage was most affected by carbon availability and not strongly influenced by the ORP or the NADH/NAD ratio. The use of a fluorometric probe for detecting intracellular NADH levels revealed several sludge responses that could be used for optimization of process control. Testing of the proposed biochemical model which accounted for two principal storage products, polyhydroxybutyric acid (PHB) and polyhydroxy valeric acid (PHV), provided evidence to suggest the glyoxylate cycle plays a central role in anaerobic PHA storage, by providing the necessary reducing power required for the storage reaction, in the normal operating U.B.C. pilot plant system. Tesing involving nutrient/inhibitor combinations demonstrated that anaerobic PHA storage is not committed exclusively to the glyoxylate cycle for a source of reducing power, since alternative sources of reducing power could also supply reducing power for the PHA storage reaction under different conditions.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat