Response to various shock loadings of the constant recycle‐sludge‐concentration activated‐sludge process

Abstract

AbstractThe stability of the model of a completely mixed activated‐sludge process holding the recycle sludge concentration, XR, as a system constant subjected to pH, temperature, potassium cyanide, and phenol shock loading was investigated. Soft‐drink bottling wastewater was used and maintained at 1000 mg/liter chemical oxygen demand (COD). The hydraulic ratio and recycle sludge concentration were maintained at 0.3 and 7000 mg/liter, respectively. An initial dilution rate of ¼ hr−1 was maintained for pH and temperature shock loading, with ¼ and ⅛ hr−1 for KCN shock loading and ¼, ⅛, and \documentclass{article}\pagestyle{empty}\begin{document}$\frac{1}{16}$\end{document} hr−1 for phenol shock loading. It was found that the present system could handle pH shock loading as low as 4.0 and as high as 10.4 without any serious disruption of biological solid concentration and filtrate COD. At pH 4.0 shock loading, filamentous organisms were predominant. Temperature shock loading could be handled from 23 to 36°C without any leakage of effluent filtrate COD. At 46°C temperature shock, a 14 hr period was required to recuperate to the new steady state and provided only 85% of COD removal efficiency. For KCN (50 mg/liger) and phenol (85 mg/liter) shock loading, the dilution rates should be lower than \documentclass{article}\pagestyle{empty}\begin{document}$\frac{1}{16}$\end{document} hr−1 in order to shorten the transient period and improve the effluent quality. Biological kinetic constants included cell yield value, maximum growth rate, and the saturation constant, which was varied with the qualitative shock applied.