酸碱与农业生物质骨料对污泥脱水效能的影响

Effects of acid and alkali and agricultural biomass as skeleton builder on sludge dewaterability

摘要:

为改善污泥脱水性能,在不同pH条件下考察3种农业生物质即小麦秸秆粉末（WSP）、玉米秸秆粉末（CSP）及稻壳粉末（RHP）对污泥脱水的影响.采用毛细吸吮时间（CST,t_CS）及污泥比阻（SRF,F_SR）等表征污泥脱水性能,用粒径和Zeta电位考察污泥性质的变化,通过离心液浊度,胞外聚合物质（EPS）含量、束缚水和泥饼结构来解释协同作用机制.实验结果显示,当pH控制在3时,污泥脱水效果最好,深度脱水后泥饼含水率下降到61.5%；分别投加WSP、CSP及RHP时,污泥F_SR分别下降到7.32×10⁸,7.41×10⁸及8.29×10⁸ s²/g.pH小于2或pH从8升高到11时t_CS和F_SR都显著升高；在投加0.75 g/g DS WSP、CSP及RHP后,也不能改善污泥脱水效果.pH低于2或者碱性条件使污泥释放更多有机物质和浊度,污泥脱水效果恶化严重.酸及生物质改善污泥脱水性能的机理为酸（pH=3）促进污泥分解EPS释放束缚水,而生物质作为骨料提供水分孔道.

Abstract:

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 (t_CS), filtration resistance (SRF, F_SR), 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, F_SR decreased to 7.32×10⁸, 7.41×10⁸, and 8.29×10⁸ s²/g, respectively. Sludge t_CS and F_SR 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.