不同化學調理搭配低溫調理對污泥脫水之影響

Abstract

隨著飲用水質標準及放流水標準之提高，淨水及廢水污泥之產量亦日漸增加。為有效提高污泥脫水效率，適當的調理行為為重要步驟。此外淨水及廢水污泥廣泛使用高分子聚合物為調理劑，但是殘餘之高分子聚合物可能對環境及人體造成影響，研發取代高分子聚合物調理之替代方案則有其必要性。 本研究分別針對淨水污泥及廢水生物污泥，以不同之調理劑，包括常用之合成高分子聚合物、無機性調理劑(PFS)及生物可分解性調理劑(幾丁聚醣)進行調理，並搭配物理性調理(低溫調理)。藉以探討不同之調理劑及低溫調理對污泥性質之影響，並以CST、SRF、界達電位及壓濾實驗評估調理後污泥之脫水特性。在脫水程序方面，利用實驗室規模之壓濾、帶濾及離心式脫水機，模擬實廠脫水狀況。 實驗結果顯示，幾丁聚醣可促進淨水污泥之脫水性，但調理效果較高分子聚合物差，只有在泥餅含水率上，有相近之結果。在生物污泥部分，幾丁聚醣在較高劑量下可達到與高分子聚合物相近之調理成效，並較無過量加藥之問題。此外生物污泥經低溫調理後，再搭配幾丁聚醣調理，可達到較佳之調理效果。在後續脫水程序中，脫水機之最適操作壓力會因脫水機型式而異，以泥餅含水率評估脫水效率，離心式脫水機之脫水效率為三者中之最高。

Because of the higher standards for drinking water and more stringent regulations for industrial effluent, sludges from water treatment plant (WTP) and wastewater treatment plant (WWTP) increase rapidly. Efficient sludge dewatering depends on appropriate conditioning. Polymer conditioning has been widely applied to WTP and WWTP sludges. Since the residual polymer may cause long term adverse effect on both environment and human health, it is necessary to search for alternatives for polymer conditioning. The study examined the conditioning efficiencies of polymer, polyferric sulphate (PFS) and chitosan, as well as low temperature treatment, on sludge dewatering. CST, SRF, ZP and water contents of sludge cakes were monitored as dewatering characteristics. Sludges were dewatered with laboratory-scale filter press, belt press and centrifuge to simulate the full scale dewatering. Experimental results indicate that although the chitosan conditioning improved the dewaterability of WTP sludge, particularly in the water content of the sludge cake, it is generally less efficient than the polymer conditioning. The chitosan, at higher dosage, achieved the same extent of dewatering on biological sludge as the polymer. Unlike the polymer, the chitosan had less overdosing effect. Better conditioning by chitosan was observed when the biological sludge was first treated with low temperature. In the study on dewatering process, various optimal pressure was discovered for each dewatering device. When evaluated with water contents of sludge cakes, centrifuge had the highest efficiency in the three dewatering devices.