活性污泥表面性质对絮凝沉降性能与出水悬浮物的影响

为了研究污水处理厂活性污泥表面性质对絮凝性能(flocculation ability,FA)和出水悬浮物(effluent suspend solid,ESS)的影响,测定了北京市7个不同污水处理厂活性污泥的表面性质,包括污泥容积指数(sludge volume index,SVI)和胞外聚合物(extracellular polymeric substance,EPS)中的蛋白质/多糖(protein/carbohydrate,P/C)比例、Zeta电位以及二维分形维数(twodimensional fractal dimension,D2f),并且通过相关性分析和拟合,探讨了这几个参数与活性污泥的FA和ESS的关系.结果表明,SVI与活性污泥的FA和ESS并不存在明显的相关关系,但FA和ESS存在明显的负线性相关关系(R_2=0.787);当EPS中的P/C从1.28增加到25.34时,FA可从0.19增加到0.73,ESS从14.89 mg·L~(-1)降低到6.08 mg·L~(-1),蛋白质中的氨基带有正电荷能够中和絮体表面的负电荷,其在EPS中所占的比例越大,有利于降低表面Zeta电位的绝对值和形成更稳定的絮体结构,进而提高絮凝能力.而且,Zeta电位与活性污泥的FA和ESS分别存在负线性相关(R_2=0.883)和正线性相关(R_2=0.902),当Zeta电位的绝对值每减小1 m V,FA提高0.059,ESS减少0.934 mg·L~(-1).此外,活性污泥的D2f与FA基本上呈现指数关系(R_2=0.935,P0.01),当D2f从1.10增加到1.45,FA提高了4.3倍,而同时D2f与ESS具有较好的负线性相关(R_2=0.868).

Influence of Activated Sludge Surface Properties on Flocculating Settling and Effluent Suspend Solid

In this paper, the influence of the surface properties of the activated sludge on flocculating settling and ESS was studied in seven different sewage treatment plants in Beijing, such as the sludge volume index (SVI), the protein/carbohydrate (P/C) ratio in extracellular polymeric substance, Zeta potential, two-dimensional fractal dimension(D_2f). The relationships between the surface properties of the activated sludge and flocculation ability (FA) or effluent suspend solid(ESS) were also analyzed. The results showed that no obvious correlation was obtained between SVI and FA or ESS, but obvious negative correlation between the FA and ESS (R²=0.787) was observed. When the P/C increased from 1.28 to 25.34, the FA could increase from 0.19 to 0.73 correspondingly, but the ESS decreased from 14.89 mg·L^-1 to 6.08 mg·L^-1. This was because the amino acids in protein with positive charge could neutralize the negative charge on the surface of floc, the increase of protein ratio in EPS could decrease the absolute value of Zeta potential, which made a contribution to form more stable floc structure, and improved the ability of flocculation. Moreover, the Zeta potential had a positive correlation with FA but a negative correlation with ESS. The absolute value of Zeta potential decreased by 1 mV, FA increased by 0.059 and ESS decreased by 0.934 mg·L^-1 correspondingly. In addition, there was an obvious index correlation (R²=0.935, P<0.01) between D_2f and FA; While D_2f increased from 1.10 to 1.45, FA could increase by 4.3 times and ESS decreased linearly (R²=0.868).