UBC Theses and Dissertations
Aerobic granular biomass using municipal primary effluent : a comparative monitoring study Woolley, Sylvia
In the past two decades, aerobic granular biomass (AGB), has proven to be a viable candidate as a biological wastewater treatment solution, and has been implemented worldwide in the Nereda® process; yet, a lack of research and application of AGB systems in North America, could hinder its application in Canada. As such, two pilot-scale, sequencing batch reactors were operated to cultivate AGB using low-strength, Canadian municipal wastewater. The study was separated into two phases, to fulfil the primary objective: (a) to see the influence of additional volatile fatty acids (VFA) on granulation; and subsequently, a secondary objective: (b) to find out if the granulation start-up time can be decreased by increasing the rate of selection pressure application. During the first phase, Reactor 2, on average, received 42% more VFA than the other, which acquired VFA solely from the primary effluent feed. Granules were observed in both reactors, however, neither system produced the smooth, dense granules expected with AGB. The granules had outgrowth on the peripheral, and the system that received additional VFA had more outgrowth and higher shape irregularity. It is understood high amounts of VFA breakthrough into the aerobic phase of the cycle led to granular instability, which was more intensely noted in the system that had higher inlet VFA concentrations (both systems ended up using similar amounts of VFA during the anaerobic phase). Preserving high biomass concentrations proved to be challenging in maintaining stability during start-up. Nutrient removal was observed consistently in both systems, but, due to high dissolved oxygen concentrations, denitrification was not achieved significantly in either system. The lack of denitrification caused limitations in orthophosphate removal with VFA competition occurring between denitrifiers and polyphosphate accumulating organisms in the subsequent anaerobic phase. Overall, it was concluded that additional VFA is not a necessity for granulation using local wastewater, during the observed season. Phase 2 was not successful in achieving granulation. Colder temperatures, lower strength wastewater and a short schedule were all factors that attributed. Valuable lessons in granular start-up were attained from Phase 2, despite the initial objective not being fulfilled.
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