High polymer demand in sludge conditioning is an intractable aspect of the water industry. This study investigated the effects of extracellular polymeric substances (EPS) fractions on polyacrylamide demand for conditioning and dewatering performance. Specifically, it examined aerobically and anaerobically digested sludges from seven full-scale wastewater treatment plants (WWTPs). Our study successfully quantified the contributions of soluble EPS to polyacrylamide demand during conditioning and explained the role of tightly bound EPS (TB-EPS) in determining the digested sludges’ dewatering performance. Results show that the concentrations of soluble EPS in the sludges varied between 92 – 1148 mg/L. Experimental results also demonstrated that between 25% - 80% of polyacrylamides used for conditioning were wasted in “parasitic” reactions with soluble EPS. The residual cationic polyacrylamide left in solution, after the parasitic reactions, was substantial and varied between 35 – 254 mg/L. Despite this outcome, the zeta potential values of dewatered sludge cakes remained negative, i.e. between -24 – -35 mV. These indicated that the residual soluble cationic polyacrylamides would not have been absorbed on the negatively charged sludge particles. This explained the relatively poor performance of the dewatering stage in the treatment plants studied. Furthermore the results suggested the TB-EPS attached to the sludge particles would be responsible for the poor dewatering. We postulated that the TB-EPS would gelify and immobilize the water surrounding the sludge particles. Our study suggested that new and more effective polymers for conditioning are needed to both: (i) reduce polymer demand; and (ii) improve the dewatering performance.

污泥处理中高聚物的需求是水工业的一个棘手的方面。这项研究调查了细胞外聚合物质（EPS）组分对聚丙烯酰胺调理和脱水性能的影响。具体来说，它检查了来自七个大型污水处理厂（WWTP）的需氧和厌氧消化的污泥。我们的研究成功地量化了调节过程中可溶性EPS对聚丙烯酰胺需求的贡献，并解释了紧密结合EPS（TB-EPS）在确定消化污泥脱水性能中的作用。结果表明，污泥中的可溶性EPS浓度在92 – 1148 mg / L之间变化。实验结果还表明，用于调理的聚丙烯酰胺中有25％-80％在与可溶性EPS的“寄生”反应中被浪费了。寄生反应后，溶液中残留的阳离子聚丙烯酰胺残留量很大，在35 – 254 mg / L之间变化。尽管取得了这一结果，脱水污泥饼的zeta电位值仍为负，即在-24 – -35 mV之间。这些表明残留的可溶性阳离子聚丙烯酰胺将不会被带负电的污泥颗粒吸收。这解释了在所研究的处理厂中脱水阶段的性能相对较差。此外，结果表明，附着在污泥颗粒上的TB-EPS可能导致脱水不良。我们假设TB-EPS会胶凝并固定污泥颗粒周围的水。我们的研究表明，需要新的，更有效的调理聚合物来实现：（i）减少聚合物需求；（ii）改善脱水性能。