| Description |
Established characteristics of aerated submerged biofilm reactors (ASBRs) include sustenance of multiple microclimates within the system, high biomass accumulation, and highly diverse bacterial population. Besides presenting important advantages over the traditional use of suspended growth activated sludge systems, these properties also make ASBRs a more suitable environment for the achievement of simultaneous carbon, nitrogen and phosphorus removal from sewage. By incorporating air cycling into their operation, simultaneous carbon and nutrient removal employing ASBRs has been well established and documented. Airon and air-off intervals promote the coexistence of aerobic, anoxic and anaerobic zones within the system, allowing the concurrentbiological metabolization of carbon, nitrogen, and phosphorus compounds. This research assessed the simultaneous carbon and nutrient removal potential of specially designed structures treating primary clarified municipal wastewater effluent at low temperatures. For this, two pilot-scale bioreactors were constructed and operated during 115. One bioreactor held a series of six dome shaped aerated submerged biofilm devices, called Poo-Gloos, while the second bioreactor held a series of six aeration bases, intended to emulate a controlling suspended growth process. With both bioreactors receiving the exact same influent wastewater constitution and flow rate, and with operational variables adjusted equally to both reactors on a weekly basis, a quantitative, qualitative and comparative analysis of the nutrient removal capacity of the two systems was performed. In terms of COD removal, average weekly percentage removals of up to 77±5% and as low as 50±5% were achieved by the Poo-Gloo system under air cycling conditions. In contrast, the control system exhibited an average weekly removal percentage range between 8±8% and 39±6%. In terms of total nitrogen (TN) removal, a consistent increase in average weekly removal percentages from 42±6% to 47±3%, and to 49±4% was observed in the case of the Poo-Gloo system conforming air-off periods were increased from 2 hours to 3 hours, and to 4 hours, respectively. In contrast, the control system exhibited an erratic behavior under air cycling conditions achieving weekly percentage removals in the range between -7±13% and 14±5%. Finally, in terms of total phosphorus (TP) removal, an optimum air cycling composition of 21 hours on/3 hours off was observed, allowing for the largest average weekly TP percentage removal achieved, 22±4%. Meanwhile, the control system accomplished an average weekly removal percentage of only 0 ±6% under the same air cycling conditions. |
