| Biological Nutrient Removal Capacity was evaluated in a full-scale study at an apartment wastewater treatment plant to introduce low cost operational and high efficient system and protect water sources from eutrofication caused by nitrogen and phosphorus. The novel BNR system, Advanced Step Aeration(ASA) system consisting of anoxic sludge tank, anaerobic, aerobic, anoxic, and aerobic tank in series with step feed was used for the study. Nutrient removals through ASA system were considerably excelent: at influent levels of T-N 40∼80㎎/ℓ, T-P 4.0∼8.0㎎/ℓ, respectively, removal efficiencies for T-N and T-P are 70∼85% and 90% and effluent levels for T-N and T-P are 10∼15㎎/ℓ and 0.4∼0.6㎎/ℓ. Step-feeding raw wastewater to anaerobic, and anoxic tank and using raw wastewater as external carbon source have brought about the improvement of denitrification capacity. Maximized phosphorus release was derived from reduction of Nitrite and Nitrate loading through additional denitrification and successful DO control, Nitrification rate(K_N) according to water temperature in aerobic tank was rather high from 0.89 to 1.27 ㎎N/gMLSS·hr in the range of 13∼18℃. Denitrifcation rate(K_(DN)) was revealed to be from 0.64 to 0.95 ㎎N/gMLSS·hr in C/N ratio of 3.6∼4.3 over 15℃ and from 0.5 to 0.77 ㎎N/gMLSS·hr in C/N ratio of 3.5∼4.0 below 15℃. In C/P ratio of 35∼58 phosphorus release rate(K_(PR)) in the anaerobic tank and phosphorus uptake rate(K_(PU)) in the anaerobic tank could be described as 3.1∼4.1㎎P/gMLSS·hr, 1.9∼2.5㎎P/gMLSS·hr, respectively. |
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