Effect of Selected Nonionic Surfactants on the Activated Sludge Morphology and Activity in a Batch System

Abstract

AbstractIn this study, two nonionic surfactants, one alcohol ethoxylate (AE) and one alkylphenol ethoxylate (APE) were investigated with regard to their influence on the morphology of activated sludge flocs, microbial activity and wastewater treatment efficiency in a laboratory batch system. The experiments were carried out for a range of nonionic surfactants concentrations in wastewater from 5 to 500 mg L−1. Additionally, these results were compared to the data obtained in previous experiments on anionics and performed under the same conditions. Both nonionics tested caused a decrease in the size of activated sludge flocs but they did not affect the shape of the flocs. The circularity index and convexity of flocs remained similar to the control run, containing no surfactant. The presence of nonionic surfactants within the tested concentrations range caused a decrease in biomass activity. In spite of morphological changes of activated sludge flocs and a decrease in microbial activity, only higher concentrations of nonionics in wastewater starting with the level of 50 mg L−1 can induce pinpoint flocs and decrease wastewater treatment efficiency. APE showed a stronger impact on the decrease in floc size and microbial activity than alcohol ethoxylate did. APE was also more difficult to biodegrade than AE. Comparing the efficiency of wastewater treatment (in terms of COD removal) in the presence of nonionic and anionic surfactants at the same concentration of 50 mg L−1, the degree of organic pollutant removal was found to be higher by about 10% for anionics than for nonionics.