好氧生物顆粒之氧氣擴散係數

Abstract

本論文中，藉由微電極儀器去量測好氧顆粒DO反應數據，並利用適合的質傳方程式去求解擴散係數。因實驗樣品不同，分為兩部分討論。第一部分，量測反應活性較小的兩種好氧顆粒，分別為貯存於4oC冰箱數個月的醋酸及酚好氧顆粒。生物外觀上觀察，可明顯看出醋酸好氧顆粒的粒徑大於酚好氧顆粒。在較高的水流流速通過好氧顆粒，減少表面質傳阻力至忽略。一維無反應質傳方程式，進行估算可發現，直徑對擴散係分為兩區：較大顆粒的醋酸好氧微顆粒，1.28-2.50 mm，具有較大的擴散係數1.24-2.28 x10-9 m2 s-1 ;較小顆粒的酚生顆粒，0.42-0.78 mm，具有較小的擴散係數2.50-7.65 x10-10 m2 s-1。 藉由微電極及雷射共軛焦顯微鏡量測，可發現好氧顆粒內部為層狀結構。穏態酚生顆粒內溶氧濃度數據說明好氧顆粒之表層具有高反應活性。考慮內部平均氧氣濃度做為邊界可求出擴散係數為1.34-1.82x10-9 m2 s-1。同時處慮非穏態及態態的溶氧數據可知，醋酸好氧顆粒表層之擴散係數為0.6-1.3x10-9 m2s-1；而酚好氧顆粒則為2.5-4.6x10-10m2s-1。由實驗結果顯示，反應及擴散圴為好氧顆粒內部氧氣傳輸的限制因素。

The dissolved oxygen (DO) concentration in aerobic granules were measured using microelectrodes, based on which the diffusivity of oxygen was thereby estimated. Considering granules of low bioactivity, the acetate-fed granules of size 1.28-2.50 mm exhibited diffusivity of 1.24-2.28 x10-9 m2 s-1; while phenol-fed granules of size 0.42-0.78 mm had diffusivities of 2.50-7.65 x10-10 m2 s-1. Based on confocal laser scanning microscope testing the interior of granules exhibited layered structure. The steady-state DO concentrations of phenol-fed granule were recorded, showing that oxygen had been depleted in the surface reacting layer of granule. The oxygen diffusivity inside this reacting layer was estimated 1.34-1.82x10-9 m2 s-1 by assuming an mean oxygen concentration. Considering both steady-state and transient DO responses, the acetate-fed granule had diffusivity of oxygen of 0.6-1.3x10-9 m2s-1, while the phenol-fed granules had diffusivity of 2.5-4.6x10-10m2s-1. Both reaction and diffusion limits the oxygen transport in aerobic granules.