Enhanced waste activated sludge dewaterability by tannic acid conditioning: Efficacy, process parameters, role and mechanism studies

Extracellular polymeric substances (EPS), especially proteins, exert a vital role in sludge dewatering. Tannic acid (TA), a plant secondary metabolite , is capable of bonding with proteins, and herein we employed it as a novel conditioner for sludge dewatering . The results indicated that TA enhanced sludge dewaterability with high reductions of 81.3% capillary suction time, 87.5% specific resistance of filtration and 13.4% water content of dewatered sludge under the optimized process parameters: TA dosage of 0.15 mmol/gTS, stirring speed of 200 r/min for 1 min, and settling time of 15 min. TA altered sludge properties pronouncedly including viscosity, particle size, zeta potential , pH and EPS contents and correlation analysis revealed their associations with sludge dewaterability. Moreover, EPS fluorescent components, sludge functional groups and surface morphology were detected for a better understanding of TA conditioning mechanism. The findings provide not only the feasibility of TA but also the potential of TA-containing plant waste in sludge treatment .