Abstract
This work was undertaken to investigate the cause of sludge acidification that led to disruption of the activated sludge process treating coking wastewater from a steel-making plant in Taiwan. An activated sludge reactor (ASR) with a working volume of 80 L was used as a model system to simulate the behavior of the real wastewater treatment process. Parameters that may cause acidification or inactivation of the sludge (NH 3, SCN −, S 2O 3 2− and CN −) were studied individually to examine for their effects on the performance of the ASR. The results show that high loading of NH 3, SCN − and CN − did not lead to pH decrease, while the ASR attained 85% COD removal and nearly 100% SCN degradation. In contrast, when the wastewater was supplemented with ca. 1000 mg/L of S 2O 3 2−, the pH dropped to nearly 4.0 in 2 days and the COD and SCN removal yields were significantly lower (at 50 and 0–20%, respectively). Thus, overloading of S 2O 3 2− was apparently a key factor causing sludge acidification. The results suggest that to ensure a normal functioning of the activated sludge, the influent S 2O 3 2− concentration should be closely monitored and that the pH control of the ASR is indispensable when the S 2O 3 2− loading is in excess.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have