Characteristics and distribution research on extracellular polymer substance extracted from sewage sludge

Extracellular polymer substance (EPS) is an important substance in sludge dewatering process and can be divided into slime, loosely bound EPS(LB-EPS) and tightly bound EPS(TB-EPS). The major components in different EPS layers in mechanical dewatered sludge (sample D) and sludge from thickening tank (sample U) were analyzed in the study. Results showed that, for all sludge samples, protein content in slime was much higher than that in LB-EPS and TB-EPS. In addition, from the results of total EPS content in four sludge samples (U: 98.68 mg gvss⁻¹, US (sample U+SDS): 135.27 mg gvss⁻¹, D:138.16 mg gvss⁻¹, DS:211.21 mg gvss⁻¹), it was found that sodium dodecyl sulfate (SDS) extracted more EPS content from sludge, which proved that SDS might cause substantial release of EPS, especially PN from sludge. Increase PS content in LB-EPS, and TB-EPS as addition of SDS, implied sensibility of cells in sludge to SDS. Differential Scanning Calorimetry found that bound water proportion in four different sludge samples ranged as follows: as D>DS>US>U. Results from other analytical techniques,such as FTIR and NMR, were also given the supported proof for the distribution changes of EPS and bound water.