Abstract
Abstract
Extracellular polymeric substances (EPS) play a key role in the activated sludge process (ASP) of wastewater treatment plants since they help bioflocculation and thus influencing sedimentation and dewatering. Previous long-term studies have examined effects of operating conditions on EPS in membrane bioreactors, while here we introduce a long-term study on activated sludge (AS) followed by gravity separation. To better understand dynamics of EPS variation and composition in the ASP, the present study focused on effects of operating conditions as well as of seasonal environmental cycles on EPS at different sampling locations along AS trains. Two ASP trains—one with full nitrification/denitrification (DN) with internal recirculation and the other with partial nitrification/DN and no recirculation—were monitored for 13 months. Results revealed that the ASP with internal recirculation had uniform EPS concentrations within the treatment train, whereas the process without internal recirculation exhibited a decreasing EPS trend along the treatment train. Concurrently, EPS concentrations in both ASP trains did not exhibit seasonality. In other words, EPS production appeared process dependent but not temperature dependent. While mean cell retention time of the AS was shown to have no effect on EPS, total inorganic nitrogen concentration from primary effluent was demonstrated to have a significant and direct relationship with EPS protein and overall EPS production.
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