Spatial Stability of Floc Blanket in Full-Scale Floc Blanket Clarifiers

實廠污泥毯澄清池中泥毯之空間分佈穩定性

宋尚軒(S. S. Sung) ； 林文煒(W. W. Lin) ； 陳兩全(L. C. Chen) ； 李篤中(D. J. Lee)

《Journal of the Chinese Institute of Chemical Engineers》 34卷4期 (2003/07) Pp. 447-456

https://doi.org/10.6967/JCICE.200307.0447

摘要

本文監控平鎮淨水廠中污泥清池泥毯隨聚氯化鋁調理劑量作階段性改變之動態行為。在原水濁度範圍7-13NTU、聚氯化鋁調理劑量由1.86 ppm陡降至0.95 ppm含鋁量時，傳統凝聚-澄清程序產生之泥毯其粒徑與固含量分佈皆發生波狀擾動之失穩現象；在傳統程序前加入前凝聚一前沉澱程序（二階段程序）則可穩定化泥毯空間分佈。杯瓶實驗顯示可與聚氯化鋁反應之有機物可能是造成泥毯失穩之主因，而動態小角度散射實驗亦支持此一假說。本文亦以線性穩定性分析闡明泥毯空間分佈對微小參數擾動之變動情形：當流體上升速度大於某極限值時泥毯空間分佈即會失穩，二階段程序可產生具較大沉降速度之大型膠羽進而穩定化泥毯分佈。

並列摘要

We monitored the dynamic responses of the blankets in the full-scale floc blanket clarifiers at PingTsan Water Works with dosed polyaluminium chloride (PACI) subjected to step-changes. With the raw water turbidity ranging 7-13 NTU, the sudden drop in PAC1 dose from 1.86 to 0.95 ppm as Al in conventional coagulation-clarification process led to a wave-like spatial instability in distributions of both solids fraction and floc size of the blanket. Adding a pre-coagulation and pre-sedimentation prior to the conventional stage (two-stage process) produced rather stable blanket that was only mildly deteriorated at insufficient coagulant dose. Jar tests with single or two-stage coagulation-sedimentation revealed that the organic matter readily interacted with dosed P ACI and might be responsible for the observed blanket structure deterioration. Dynamic flocculation tests using smallangle light scattering technique support this speculation. Linear stability analysis was conducted to demonstrate the blanket stability at infinitesimal process parameter change. The blanket would become linearly unstable at an upflow velocity exceeding a threshold value. Two-stage process produced large floes, which exhibit high settling velocity, hence stabilizing the blanket clarification process.

並列關鍵字

Flocculation clarifier ； Blanket ； Organic matter ； Stability analysis