回分式活性汚泥処理におけるリン除去過程のモデル解析

流入下水の有機物組成と撹拌工程に残存する硝酸性窒素の影響

抄録

An anaerobic/aerobic sequencing batch activated sludge reactor was operated by using synthetic wastewater consisted of peptone and glucose as carbon sources. The response of phosphorus release and uptake to different carbon sources was investigated by conducting three different experiments. After achieving a good biological phosphorus removal, the organic substrates were changed solely to glucose, to peptone and to sodium acetate respectively. It was found out that the wastewater having sodium acetate yielded highest phosphorus release and that peptone gave the lowest. The difference in the phosphorus release and uptake was appeared to be strongly dependent on organic substrate composition in relation to hydrolysis and fermentation process.
Other sets of experiment were also performed to investigate the effect of remaining nitrate at mixing phase on phosphorus removal. Nitrate concentrations were adjusted to 10 and 20 mg-N/L at the initial mixing phase. It was found out that the nitrate addition suppressed phosphorus release during a whole mixing phase, the less phosphorus release with limited PHA storage seemed to increase effluent phosphorus concentration afterwards. Therefore in order to achieve reliable phosphorus removal, the nitrate at the beginning of initial feed/mixing phase should be as low as possible. A SBR model based on IAWQ ASM2 was applied to explain the phosphorus and nitrate dynamics in the response experiments that were carried out for continuous period of 28 days. The long-term simulation results well explain the dynamics of phosphorus and nitrogen during a cycle as well as effluent water quality, when denitrification process by Poly-phosphate Accumulating Organisms was considered and kinetic parameters were adjusted for the synthetic organic substrates.