ABSTRACT
Sludge dewaterability was chemically and morphologically explored during sewage sludge treatment by vermifiltration. The results, with a conventional biofilter (BF, no earthworms) as a control, demonstrated that the capillary suction time(CST) and specific resistance of filtration(SRF) of vermifilter (VF, with earthworms) treated sludge were 64.9±1.7s and (23.1±1.3)×1012m/kg,16.8% and 36.0% lower than that of the BF, respectively. Additionally, the VF could efficiently decompose loosely bound extracellular polymeric substances (LB-EPS), releasing more water trapped inside biofilm. Furthermore, the VF enable to reduce the electrostatic repulsive forces between particles, verified by 9.61±0.19mV of the absolute value of zeta potential, 19.6% lower than that of the BF. Notably, based on scanning electron microscopy (SEM) analysis, the fractal dimension (Df) of sludge floc structure stated that more small and loose sludge flocs tended to aggregate into bigger inorganic particles. Therefore sludge flocs with highly compacted structure and smooth surface can transform part of vicinal water and water of hydration into easier-removed interstitial water, improving the dewaterability.
