Effects of Activated Sludge Process Conditions on the Production of Extracellular Polymeric Substances: Results of Yearlong Monitoring in a Warm Climate

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.

Naturally occurring nanoparticles in two biological wastewater treatment plants in Southern California

“…Plant 1 was operating with an MLE with recirculation, which would render the ow in the biological treatment similar to a continuous stirred tank reactor (CSTR). (Tseng et al 2015) In contrast, Plant 2 was operating with an L-E with a ow resembling a plug ow. This may explain the signi cant correlation between EPS and their components with CR and Z avg in Plant 2 but not in Plant 1, since the recirculation in Plant 1 mixed the ow, it would be di cult to assess the relationship between EPS and CR or EPS and Z avg in the biological treatment (Table 1, Fig.…”

Seasonal occurrence and fate of nanoparticles in two biological wastewater treatment plants in Southern California

“…Each EPS fraction was quantified by its protein and polysaccharide content using the procedures from the Lowry et al (1951) assay and DuBois et al (1956), respectively. Since this study sought to examine the occurrence of nano‐sized particles with the production (not the morphology) of EPS in the wastewater, we only sought to analyze major EPS components found in a previous study, polysaccharides, and protein (Tseng et al, 2015).…”

“…For the EPS analysis, EPSs of the activated sludge were extracted according to Li and Yang (2007) and Tseng et al (2015) and separated into loosely bound (LB EPS) and tightly bound (TB EPS) fractions. Briefly, 50 ml of well-mixed sludge samples was transferred to 50-ml polypropylene centrifuge tubes and underwent 5 min of centrifugation at 4Á10 3 g. The supernatant was discarded and replaced with the same volume using a F I G U R E 1 Schematic of the process configuration of Plants 1 and 2.…”

Characterization of extracellular polymeric substances produced during nitrate removal by a thermophilic bacterium Chelatococcus daeguensis TAD1 in batch cultures

“…5 There are numerous studies on how operational conditions (e.g., dissolved oxygen, temperature and pH) inuence the composition and the distribution of EPS in biolms or activated sludge. [6][7][8] However, reports about the characteristics and the distribution of EPS of thermophilic nitrogen removal process have rarely been seen according to our knowledge. 9 Bacterial occulation is highly related to EPS.…”