The primary objective of this research was to determine if efficient biological phosphorus removal could be established under low sludge retention time of 2 days and a nominal hydraulic retention time of 4 to 6 hours. The two-stage Phoredox process was selected because of the practical application of retrofitting high rate treatment plants to achieve bio-P removal without the additional tankage required for an anoxic section and the additional expense of a recycle system. It has been shown that nitrate recycled into the anaerobic reactor impacts on bio-P removal and the two-stage Phoredox process provides no control over nitrates entering the anaerobic reactor. Therefore a secondary objective of this research was to determine if a low sludge retention time mode of operation could be used as an effective way to prevent nitrification in the activated sludge treatment process. Another objective was to observe mixed liquor settling characteristics of the two-stage Phoredox process operated under high rate conditions. A pilot scale two-stage Phoredox activated sludge treatment process operating under high rate conditions was used to meet these objectives. The desired bio-P removal biomass was not observed under SRT operating conditions of 2, 3 and 5 days. Partway into the research a sludge bulking condition developed which was identified as filamentous growth. On two occasions this severe filamentous growth resulted in the process failing and the system being restarted. On one occasion after the system was restarted using a seed sludge from a three-stage Phoredox pilot plant, a bio-P removal biomass was present. This condition only lasted for a short period and ended as filamentous growth began to become dominant. The process failed because of this phenomenon. The system was restarted using a seed sludge and again filamentous growth dominated. Chlorine addition was found to be the only method to control this phenomenon and was continued to the end of the research. The desired bio-P removal biomass was not observed even during the last period of the research when the SRT was increased to 8 days. During this research a stable bio-P removal biomass was not established. For a short period a bio-P removal biomass was present but failed to persist. Nitrification never became established at any time. Sludge settleability was poor due to filamentous growth which developed partway into the research and was present throughout the remainder of the study. Chlorine addition was the only method found that remedied this settling problem. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The objective of this research was to optimize the bio-P process as applied to a weak sewage with respect to HRT in each of the process zones. This goal was to be achieved by changing the HRT of the various zones with all other operating characteristics being held constant. The experimental work during this study involved two initially identical process trains operated in the University of Cape Town (UCT) mode. The aerobic zones of both trains were divided into four equal sized complete-mix cells to allow observations of phosphate uptake and poly-β-hydroxyalkanoate (PHA) consumption under aerobic conditions. After steady-state was established, the anaerobic HRT was reduced to 50% of the original value in the experimental module by reducing the anaerobic reactor volume. At the same time, the mixed liquor of both trains was drained, mixed and reapportioned to the two processes, thereby assuring equivalent starting conditions. Results of this study showed that both processes performed identically prior to the anaerobic HRT change. After the anaerobic HRT change, there was a forty day period where P removal and effluent P were the same in both process trains. This was so, even though the anaerobic P release was considerably less in the experimental module. Subsequently, a change in influent sewage type corresponded to a change in P removal and effluent P in the two process trains. An examination of the process parameters showed that the anoxic zone of the experimental module, after the anaerobic HRT change and the sewage change, consistently removed less P or released more P than in the control module. As a result, the control module out-performed the experimental module. Batch tests and tests to better characterize the influent sewage were then conducted in an attempt to determine the reasons for the different P removal characteristics. Under the test conditions, it appeared that the original anaerobic HRT was excessive. This was preferable to an insufficient anaerobic HRT, such as in the experimental module, however. The anoxic zone may have been too large, too small or just right for optimum P removal depending on the influent sewage characteristics. Optimizing the bio-P process by reducing the aerobic zone HRT appeared to have the greatest potential. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

This thesis assesses the potential for enhanced biological phosphorus (Bio-P) removal in Canadian wastewater treatment plants. Retrofit designs incorporating Bio-P removal were prepared for nine wastewater treatment plants across Canada, and were compared against chemical phosphorus removal technologies. Incremental capital and operating costs were calculated and internal rates of return (IRR's) for the capital investment required to install the Bio-P removal facilities were calculated. Based on these results, an assessment of the potential use for the technology in Canada is made. Of the nine plants studied, results indicate that Bio-P removal is economically superior to chemical phosphorus removal for the Calgary Bonnybrook, Edmonton Gold Bar, Saskatoon Mclvor Weir and Regina wastewater treatment plants. In general, Bio-P removal appears to offer significant economic advantages to plants located in Alberta and Saskatchewan because of the high cost of phosphorus removal chemicals in these provinces. The present low cost of phosphorus removal chemicals in Ontario and Quebec likely limits the viability of Bio-P removal to large (greater than 300,000 m³/d), suitably configured plants. In British Columbia, where Bio-P removal is presently used in the Okanagan Valley, the absence of widespread provincial phosphorus removal standards makes future Bio-P installations unlikely. The potential for Bio-P removal in Manitoba, the Maritimes and the Yukon and Northwest Territories is again limited by the absence of phosphorus removal standards in these parts of Canada. Results also indicate that the use of an anoxic/anaerobic/ aerobic process in the bioreactor, in conjunction with primary sludge fermentation through gravity thickening, is very applicable to Canadian plants and offers potential capital and operating cost savings relative to other Bio-P processes. The common practice of anaerobic sludge digestion, combined with sludge dewatering and land application, was found to be unfavourable from a Bio-P perspective unless the resulting supernatant/filtrate streams can be re-used or disposed of outside of the mainstream treatment process. Through the preparation of the retrofit designs, it was determined that certain aspects of Bio-P technology require additional research in order to optimize treatment plant design. These include kinetic modelling; short SRT Bio-P removal; the anorexic/anaerobic/aerobic process; the use of gravity thickening for primary sludge fermentation; and phosphorus release during anaerobic digestion. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The objective of this investigation was to evaluate Holmberg's method for simultaneous dissolved oxygen control and parameter estimation in a completely mixed diffused air activated sludge reactor.

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<p> Gel filtration chromatography on Sephadex gels G15 and G50, was used to characterize the residual organic materials found in effluents from biological treatment. Molecular weight distributions were determined as the equivalent molecular weight distribution of a homologous series of sugars and alcohols. The homologous series was also used to determine equivalent molecular radii, based on Corey-Pauling-Koltun space filling models of the homolgous series.</p> <p> To determine the distributions of residual organics from mixed cultures grown on simple, pure substrates, laboratory batch studies were performed. For this purpose, media containing glucose or glutamic acid substrates and a bicarbonate-phosphate buffer system were innoculated with activated sludge. Both high and low substrate and microorganism concentrations were used at constant temperature and pH. As a comparison for the mixed cultures, a representative strain of Flavobacterium sp. isolated from activated sludge was grown in pure culture on glucose.</p> <p> Both the laboratory mixed culture effluents and treatment plant effluents contained material of equivalent molecular weight less than 1500. However, little similarity appeared to exist between the low molecular weight (<1500) distributions of treatment plant effluents and those from the mixed cultures. A significant fraction of the treatment plant and batch effluents had equivalent molecular weights of greater than 10,000. The pure culture studies showed that a single strain of bacteria can produce material of equivalent molecular weight both greater and less than 1500.</p> / Thesis / Master of Engineering (MEngr)

Design considerations and operating procedures were investigated for nitrogen removal in an extended aeration-denitrification facility. Both past and present removal efficiencies were evaluated for the facility, along with capital and operating cost data. The findings of this research indicate that at very long detention times, significant nitrification and denitrification occurred in the plant without the use of chemicals. Overall nitrogen, BOD5, and suspended solids removals were extremely high. The significance of this research is that future plants may achieve high rates of nitrogen removal through innovative design and operating procedures without the use of costly chemicals. However, capital costs needed to achieve longer detention items will have to be evaluated for the individual plant.