Insights into the resistance of different extracellular polymeric substance (EPS) layers to the fermentation environment in sludge anaerobic digestion

Enhancing volatile fatty acids production from waste activated sludge: The role of pretreatment by N,N-bis(carboxymethyl)-l-glutamate (GLDA)

“…However, the intensity of this peak gradually increased with increasing GLDA dosage, indicating that the C O group in the chelating agent might contribute to this peak. In addition, the relationship between different functional groups in sludge samples pretreated with GLDA was verified by FTIR 2-COS maps [ 9 ]. As shown in Fig.…”

“…The exposed hydrophobic sites might benefit bacteria to contact and utilize the organics in sludge. Considering that the hydrogen bond (about 2 kcal mol −1 ) is the main force for maintaining secondary structure, it may also suggest that GLDA pretreatment could damage the hydrogen bond of sludge protein [ 9 ], which further reduces the energy barrier required for sludge hydrolysis.…”

“…The initial weight loss in WAS is attributed to moisture evaporation, including cellular and external bound water. Further weight reduction within the range of 240–600 °C can be attributed to destroying the organic fractions of sludge, such as proteins, polysaccharides, lipids, and humic acids [ 9 ]. This indicated that the pretreatment imposed little effect on the thermos-stability of the WAS flocs.…”

“…The original and secondary derivative FTIR spectra were obtained at 4000–400 cm −1 with an FTIR spectrometer (Nicolet iS20, Thermo Scientific, USA). Then, two-dimensional correlation spectroscopy (2D-COS) was adopted to improve the spectral resolution and characterize the change order of different functional groups of all the samples [ 9 ].…”

“…The solubilization and hydrolysis processes are commonly regarded as the rate-limiting steps of anaerobic fermentation owing to the stable semi-rigid structure of WAS flocs [ 7 , 8 ]. WAS comprises bacterial cells, extracellular polymeric substances (EPS), and other organic or inorganic components [ 9 ]. Among them, EPS is regarded as the backbone of WAS and is responsible for its stability [ 8 ].…”