Characteristics of extracellular polymeric substances from sludge and biofilm in a simultaneous nitrification and denitrification system under high salinity stress

Abstract

The composition and distribution of extracellular polymeric substance (EPS) both from suspended sludge and attached biofilm were investigated in a simultaneous nitrification and denitrification (SND) system with the increase of the salinity from 1.0 to 3.0 %. Fourier-transform infrared (FTIR) spectroscopy and three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy were used to examine proteins (PN), polysaccharides (PS) and humic substances (HS) present in EPS. High total nitrogen removal (above 83.9 %) via SND was obtained in the salinity range of 1.0-2.5 %. Total EPS in the sludge increased from 150.2 to 200.6 mg/gVSS with the increase of salinity from 1.0 to 3.0 %, whereas the corresponding values in the biofilm achieved the maximum of 288.6 mg/g VSS at 2.0 % salinity. Dominant composition of EPS was detected as HS in both sludge and biofilm, having the percentages of 50.6-68.6 and 41.1-69.9 % in total EPS, respectively. Both PN and PS contents in soluble EPS (S-EPS), loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) of sludge and biofilm increased with the increased salinity. The FTIR spectrum and 3D-EEM fluorescence spectroscopy of S-EPS, LB-EPS and TB-EPS in the sludge and biofilm showed the changes of functional groups and conformations of the compositions in EPS with the increase of salinity. The results demonstrated that the characteristics of EPS varied from sludge to biofilm. The obtained results could provide a better understanding of the salinity effect on the EPS characteristics in a SND system.

Potential causes of high performance of pure-oxygen aerobic granules in SBR under high organic loading condition

“…High EPS content play an essential role in formation of POAG and maintaining the integrity and stability of spatial structure in mature POAG (Badireddy et al, 2010;Zhao et al, 2016). The variations of EPS for POAS, AAG and AAS are consistent with the trends of their biomass (Fig.…”

“…The results show that pure-oxygen aeration makes POAG harboring compact and sequential structure to promote high DO penetrated into the interior of granules and metabolic products expelled from inside (Meerburg et al, 2016;Zhao et al, 2016). It is favorable to aerobic bacteria growth in POAG (Adav et al, 2010;Bernat et al, 2017;Calderon et al, 2012;Chen et al, 2003), and endures high shock and perturbations from HOLC.…”

“…The samples for analyses of EPS, catalase and dehydrogenase activities in sludge and granules were collected at the end of each SBR cycle. The EPS were extracted using a heat extraction method (Zhao et al, 2016). The polysaccharides (PS) content in the EPS was measured using the Anthrone method (Adav et al, 2008) with glucose as the standard.…”

“…It is characteristics of abundant biodiversity (Adav et al, 2009;Bernat et al, 2017;Meerburg et al, 2016), a dense and strong microbial structure (Adav et al, 2008;Moy et al, 2002), elevated activity of enzymes (Li and Chróst, 2006;Matyja et al, 2016;Tarjányi-Szikora et al, 2013;Yao et al, 2010Yao et al, , 2012Zhang et al, 2016) and a great plenty of EPS secretion (Badireddy et al, 2010;Caudan et al, 2014;Liu et al, 2004;Zhao et al, 2016;Zhu et al, 2012), which makes it harbor good performance under HOLC.…”

“…High organic loading wastewater with complex ingredients and usually over 2000 mg COD L -1 is a great challenge to prevail biological methods in wastewater treatment (Adav et al, 2010;Liu and Tay, 2015;Farzadkia et al, 2016;Moy et al, 2002;Pal et al, 2014;Ramos et al, 2016;Zhao et al, 2016;Zheng et al, 2006). Conventional aerobic granules are usually cultivated by air aeration (Adav et al, 2009;Caudan et al, 2014;Li et al, 2008).…”