Effects of salinity on the morphological characteristics of aerobic granules

Abstract

Saline wastewater is ubiquitous in industries. The present study reports the effects of salinity on the morphological properties of aerobic granules. Within a wide range of salinity from 1% to 5%, good aerobic granules were successively cultured in sequencing batch reactors (SBRs). It was found by scanning electron microscope (SEM) analysis that the granular surface turned to be smoother and more regular with increase of salinity, and under lower salinity (1%) the microbe was cocci-dominated, while under higher salinity (5%) the microbe was filaments-dominated. As a result of size distribution analysis, the granules were found to grow faster, larger and with a wider size spectrum under higher salinity. However, the porosities of the granules under the salinity of 1%, 2.5% and 5% were 0.90, 0.89 and 0.82, respectively, indicating that higher salinity may result in more compact granules. It can be concluded from this study that formation of large and compact granules is possible under salinity as high as 5% and filamentous microorganisms did not necessary lead to sludge bulking and granule breakage.

Long-term impact of salinity on the performance and microbial population of an aerobic granular reactor treating a high-strength aromatic wastewater

“…This transformation seemed to be caused by the high salinity of the wastewater, but other studies treating readily biodegradable substrates found the opposite effect since a high salinity (33-50 g NaCl L -1 ) produced a compaction of the aerobic granules (Li and Wang, 2008;Pronk et al, 2013). The difference between these studies and this one lies in the kind of organic matter treated.…”

“…To the best of the authors knowledge, aerobic granules have been usually used for treating a single toxic/recalcitrant compound and a single salt (usually NaCl) (Li and Wang, 2008;Pronk et al, 2013;Taheri et al, 2012;Wan et al, 2014). Moreover, these studies have been carried out in sequencing batch reactors (SBRs).…”

Effects of salinity on performance, extracellular polymeric substances and microbial community of an aerobic granular sequencing batch reactor

“…Figueroa et al [7] reported that the GSBR could achieve complete organic matter removal in the presence of nitrification-denitrification activities in the treatment of fish canning effluent with 30 g L À1 NaCl. Some researches illustrated that the compact granular sludge can form at 5% salinity in the influent, whereas filamentous microorganisms in the granular sludge do not lead to sludge bulking and breakage [8,9]. Pronk et al [10] observed that ammonium oxidation was not affected in the GSBR by an increase in Cl À from 0.2 to 20 g L À1 in the influent, whereas nitrite oxidation was http://dx.doi.org/10.1016/j.seppur.2015.02.042 1383-5866/Ó 2015 Elsevier B.V. All rights reserved.…”

Gradual adaptation to salt and dissolved oxygen: Strategies to minimize adverse effect of salinity on aerobic granular sludge

“…Using flocculent activated sludge as inoculum, it took 75 days for mature granules to form at salinity of 11-15 g/L NaCl. Li and Wang (2008) reported that granules grew faster and larger at high (50 g/L NaCl) than low salinity (10 g/L NaCl). This disagreement in the above results could be attributed to the difference in the operational mode, salt concentration and substrates composition.…”