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Effects of varying environmental conditions on performance of completely autotrophic nitrogen removal from dewatered sludge liquors Wu, Chumeng


Centrate, an ammonia rich wastewater, usually contains high concentrations of ammonia (around 1000 mg/L) and accounts for about 20% of total nitrogen loading to wastewater treatment plants. However, the conventional nitrification/denitrification approach for centrate treatment is costly to operate and releases a large quantity of carbon dioxide, due to the addition of organic compounds for denitrification. A brand new approach for nitrogen management is a novel process called anaerobic ammonium oxidation (ANAMMOX). ANAMMOX offers a cost effective solution for centrate treatment. Compared to the conventional biological nitrogen removal process, ANAMMOX can save 63% oxygen and 100% exogenous carbon source usage. In this research, a 400 L pilot-scale CANON SBR was studied at the J.A.M.E.S. WWTP in Abbotsford, B.C. and tested for treating on-site centrate. During 317 days of reactor running period, maximum ammonia removal rate (ARR) of 98.9 % was achieved with an average ARR of 91.0%. The reactor also achieved a maximum of 0.81 kgN/m³•d ammonia loading rate (ALR) with a minimum hydraulic retention time (HRT) of 1.46 d. The performance of the CANON SBR was highly influenced by environmental conditions. Better reactor performance was achieved at the highest tested temperature of 32ºC and maximum air flow rate of 14 L/min. Testing under 26ºC would reduce ARR by 12% and generate high nitrite concentration peaks. Compared to an airflow rate of 10 L/min, the ARR was increased by 9% and HRT was reduced by 10%, at 14 L/min. Higher initial ammonia concentrations in the reactor could also lead to better reactor performance. A maximum nitrogen removal rate of 0.36 kgN/m³•d and minimum HRT of 1.79 d was achieved at the highest initial ammonia concentration of 455 mg/L. The feeding rate did not affect the results of nitrogen removal. However, slow feeding with 500 mL/min did not create any nitrite concentration peak during the reaction. Solids concentrations in the reactor could be effectively controlled by sludge settling time. Sludge settling times between 4 to 10 min were recommended, for achieving purposes of sludge enrichment or system optimization.

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