Early warning activated sludge bulking by margin of safety for processing indicators in municipal sewage treatment plant.

Activated sludge (AS) bulking is a thorny problem which leads to serious issues in municipal sewage treatment plant (MSTP). An approach based on the margin of safety (MOS) was proposed to alarm AS bulking. Chemical oxygen demand (COD) serving as a representative chemical index for effluent was introduced to obtain the MOS. It was shown that the area of observation was divided into safety, alarm, and risk zones by the MOS with a range of COD between 25.63 and 50.00 mg L–1. The MOS of invertase under the influence of bisphenol A and triclosan was 534.40~902.59 mg L–1 and 904.91~1,870.81 mg L–1, respectively. The goodness of fit to the practical situations for the MOS of COD in several MSTPs was further certified. The MOS-based method using different types of indicators to predict AS bulking demonstrated many advantages of precision, ease-of-use, and feasibility in complex situations. The findings in this work are valuable to evaluate the environmental risks of emerging organic contaminants and the disturbance risks of sewage treatment processes. [ABSTRACT FROM AUTHOR]