| Recently in Korea and developed countries, nitrogen(N) and phosphorus(P) removal are the main target to improve effluent qualities, in order to protect discharge basins from eutrofication by N and P. Introduction of an advanced treatment function to existing wastewater treatment systems, which can be removed nitrogen(N) and phosphorus(P) as well as biochemical oxygen denrind(BOD), chemical oxygen demand(COD), and suspended solids(SS), have been required to protect water resources from domestic and industrial wastewaters. In the existing single-sludge activated-sludge system, the important factors to be considered to convert existing system into advanced treatment system are economics and efficiencies such as cost of construction and operation, easiness of operation, and stability in treatment. Using Step Feed Anaerobic Aerobic System with Anoxic Slugge Process designed by author, which consist of anoxic sludge process, anaerobic, aerobic, anoxic, and aerobic processes, the goal of this research is to investigate the possibility to retrofit conventional activated-sludge system to advanced treatment system and to assess treatment characteristics. Pilot-scale plant experiment was performed with actual municipal wastewater. Based on the results of the experiments, for interface settling test in clarifier, surface loading was 43㎥/㎡/d and minimum sludge ratio was 0.22 at design MLSS concentration of 3,000㎎/ℓ. Linear equation of nitrification-rate constant｛Kn=0.7056.exp(0.0381.T)｝ was given from correlation of Kn and temperature. The percentage of organic removals were BOD 90∼93%, COD 80∼89%, and SS 85∼98%. At influent levels of T-N 19.2∼37.5㎎/ℓ and PO₄-P 0.49∼1.66㎎/ℓ, nutrients removal were very effective in the range of NH₄-N 76∼98%, T-N 70∼92% and PO₄-P 90∼99%, respectively. |
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