Study on Improving Sludge Dewatering Efficiency by Addition of Conditioning Aids

單以飛灰助濾進行物理調理時，對於 無機污泥之脫水效率有較顯著的提升，對 於生物污泥之脫水效率則無顯著影響。添 加飛灰助濾，配合高分子聚合物進行雙重 調理時，在離心脫水試驗及帶濾脫水試驗 中，顯示對於無機污泥而言，與單獨使用 高分子聚合物比較，雙重調理能減少高分 子聚合物的加藥量，並提升污泥之脫水效 率，增加污泥餅的固含量。然而對於生物 污泥而言，雙重調理相對於單獨化學調 理，添加飛灰助濾對於生物污泥脫水效率 並無顯著效應，污泥餅固含量僅隨著飛灰 添加而增加。 污泥以離心機脫水時，毛細汲取時間 與比阻抗為較佳之脫水指標，然而對於帶 濾脫水機而言，以毛細汲取時間、比阻抗 及壓縮係數作為脫水指標，則容易產生加 藥不足之現象。Fly ash from coal-fired power plant can be used as filter aid in sludge conditioning. The scope of this research includes the dewatering characteristics and the rheological properties of conditioning sludge with fly ash / polymer. Physical conditioning with fly ash addition can improve the dewaterability of inorganic sludge, but there is no profound influence on activated sludge. The effect of dual conditioning with fly ash and polymer comparing to a sole chemical conditioning with polymer is investigated. According to the experiment with centrifugation and belt filter press, dual conditioning for inorganic sludge can reduce the dosage of polymer, improve the dewaterability, and produce higher cake solid concentration. However, when comparing dual conditioning to a sole chemical conditioning, fly ash addition shows no significant effect in activatedsludge dewatering, and cake solid concentration just increases as adding fly ash. Capillary suction time (CST) and specific resistance to filtration (SRF)are better criteria for optimal dosage of polymer in dewatering process of centrifuge. However, dosage of polymer is usually insufficient in dewatering process of belt filter press when using CST, SRF, and coefficient of compressibility as operational parameters. In the measurement of the rheological behaviors of sludge, optimal fly ash addition can reduce yield stress, apparent viscosity of inorganic sludge and improve the dewatering characteristic. However, the behavior is not observed in activated sludge conditioning with fly ash addition. As addition of polymer for chemical conditioning or dual conditioning, the relationship between shear rate and shear stress of inorganic sludge changes from straight line to curve with an obvious peak by flocculating the small particles into large and stronger aggregates, but this relationship remains linear for activated sludge. Furthermore, when sludge is treated by chemical or dual conditioning process, both of yield stress and apparent viscosity are increased in underdosing which is attributed to the floc volume and floc strength: The increases are also happened made the condition of overdosing which is due to the polymer residual in the water. According to the experimental result, the turning point showed in yield stress and apparent viscosity curves could be used as operational criterion for optimal dosage of polymer