Effect of Residence Times and Flow Reversal on Effluent Quality from Reversible Flow Biological Denitrification Reactors
Abstract:This paper reports the results of a fixed-film, two-stage, reversible flow biological denitrification reactor system operated under flow reversal cycles and decreasing residence times for the removal of nitrate from contaminated groundwater. In this system, the second-stage (i.e., follow) reactor is operated in series with the first-stage (i.e., lead) reactor. After a given operational period, the flow regime is reversed so that the follow reactor becomes the lead and vice versa. The reversible flow system was found to be effective in reducing effluent nitrate, nitrite, soluble chemical oxygen demand (SCOD), and total suspended solids concentrations when operated at residence times as short as 30 minutes. Results demonstrate the ability of this system to withstand the stresses associated with low hydraulic residence times and short flow cycles. The 30-minute residence time had the shortest flow reversal adaptation period than other longer residence times. The rapid acclimation was attributed to biofilm population adaptations and to breakthrough of nitrate and SCOD from the lead reactor, allowing the follow reactor biomass to remain more active with respect to denitrification. The shorter residence times translate to reductions in capital cost on scaled-up systems.
Document Type: Research Article
Publication date: September 1, 2000
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