Abstract
To investigate the effect of free ammonia (FA) on the nitrogen removal performance, extracellular polymeric substances (EPSs), and physicochemical properties of activated sludge, four laboratory-scale sequencing batch reactors (SBRs) were operated at FA concentrations of 0.5, 5, 10, and 15 mg/L (R0.5, R5, R10, and R15, respectively). Results showed that nitrogen removal and the production of EPSs and their components (including polysaccharides, proteins, and nucleic acid) significantly increased with the increased FA concentration from 0.5 to 10 mg/L; however, they decreased with a further increase in FA to 15 mg/L. Moreover, the capillary suction time (CST), specific resistance of filtration (SRF), and sludge volume index (SVI) decreased when FA concentration increased, indicating that better settleability and dewaterability of activated sludge was obtained. Additionally, a path diagram showed that Nitrosomonas was positively correlated, while Denitratisoma was negatively correlated with EPSs and their components. Thauera was positively correlated, while Zoogloea was negatively correlated with the settleability and de-waterability of activated sludge.
Highlights
There must be a certain concentration of free ammonia (FA), because that FA mainly depends on the ammonia concentration, temperature, and pH value of the wastewater [6]
In specific resistance of filtration (SRF) between the two FA concentrations, except between 10 and 15 mg/L (ANOVA, p < 0.05, Figure 4c). These results clearly indicate that changes in influent FA concentration have an impact on the performance of sludge–water separation
This paper presents a comprehensive insight into the response of Extracellular polymeric substances (EPSs) and their components, as well as sludge characteristics to different FA concentrations
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Activated sludge was regarded as the core functional body in biological wastewater treatment plants (WWTPs) [1,2,3]. Extracellular polymeric substances (EPSs) that accounted for 80% of the activated sludge matrix are types of metabolism or lysis of microorganisms, which play a significant role in the composition of activated sludge [4,5]. Ammonia nitrogen, as a kind of main pollutant, widely exists in various wastewaters. There must be a certain concentration of free ammonia (FA), because that FA mainly depends on the ammonia concentration, temperature, and pH value of the wastewater [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
