Conference Publication Details
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Rodgers, M., Wu, G., Clifford, E., and O’Reilly, E.
2nd Irish Conference on Constructed Wetlands
Nitrogen and phosphorus removal from wastewater using a horizontal-flow biofilm reactor and an alternating pumped-flow biofilm reactor.
2010
October
Published
1
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A novel horizontal-flow biofilm reactor (HFBR) and a novel alternating pumped-flow biofilm reactor (APFBR) were investigated for the removal of nutrients from domestic–strength synthetic wastewater (DSWW) in the laboratory and from municipal wastewater on-site. The HFBR technology is suitable for the removal of organic carbon and nitrogen in wastewaters from single houses while the APFBR technology is suitable for the removal of organic carbon, nitrogen and phosphorus from municipal wastewaters from villages and towns. The HFBR comprised a stack of 60 horizontal polystyrene sheets along which the wastewater flowed, over and back on alternate sheets, and down through the stack. The laboratory HFBR was fed with DSWW for 10 minutes each hour at a footprint loading rate of 418.4 L/m2.day, which was applied at Sheet 1 (67 % of the flow), and at Sheet 38 (33 % of the flow) to facilitate denitrification. Removals of 85.7 % chemical oxygen demand (COD), 97.4 % 5-day biochemical oxygen demand (BOD5) and 61.7 % total nitrogen (TN) were recorded for the HFBR. The laboratory APFBR comprised two 16.5 L reactor tanks (Reactors 1 and 2) with two identical biofilm modules of vertical tubular plastic media, one in each tank with a surface area of 2 m2. The APFBR operating cycle had fill, anaerobic, aerobic and draw phases, in sequence. During the fill phase, Reactor 1 was half-filled with DSWW. In the anaerobic phase, most of the phosphorus release occurred from the submerged biofilm in Reactor 1. In the extended aerobic phase, the wastewater was circulated by pumps between Reactors 1 and 2, resulting in denitrification at the start of this phase due to low oxygen concentrations, followed by nitrification and luxury uptake of phosphorus when oxygen concentrations increased. During the draw phase, Reactor 2 was half-emptied of the treated water. At the COD, TN and total phosphorus (TP) loading rates on the total biofilm area of 3.20 g COD, 0.33 g TN and 0.06 g TP /m2 .d, removals were 97% COD, 85% TN and 92% TP. Preliminary on-site studies confirmed the efficacy of the HFBR and APFBR technologies.
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