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An assessment of the potential for biological phosphorus removal in Canadian wastewater treatment plants

University of British Columbia

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.

Text

2010-09-16

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http://hdl.handle.net/2429/28507

Civil Engineering

University of British Columbia

Graduate