Three agricultural biomasses

wheat stalk powder (WSP)

corn stalk powder (CSP)

and rice husk powder (RHP) were used to enhance sludge dewaterability at different pH values. Capillary suction time (tCS)

filtration resistance (SRF

FSR)

etc. were used to characterize sludge dewatering performance. Sludge particle size and Zeta potential were investigated to reflect the changes of sludge properties. Turbidity

extracellular polymeric substance (EPS)

bound water

and sludge cake structure were used to explain the mechanism of synergistic effect. The results showed that the optimum sludge dewatering performance was achieved when the pH value was 3 with a dewatered sludge cake moisture content of 61.5% under 2 MPa pressure. When WSP

CSP

and RHP were dosed separately

FSR decreased to 7.32×108

7.41×108

and 8.29×108 s2/g

respectively. Sludge tCS and FSR increased remarkably with pH values lower than 2 or ranging from 8 to 11

and 0.75 g/g DS biomass could not improve sludge dewaterability

especially under strong alkali conditions. Strong acidity and alkali made sludge release more turbidity and organic matter which would block sludge cake and filter medium. The mechanism of acid and biomass improving the sludge dewatering performance of sludge is that acid (pH=3) promotes sludge extracellular polymerization (EPS) decomposition

while biomass provides water pore channels for dewatering as skeleton builder.