UASB反應器處理低濃度廢水之質傳及動力行為

Mass transfer and kinetic behavior of UASB reactors treating low-strength wastewater

賴逸軒(Yi-Syuan Lai)

指導教授 ： 黃汝賢

共同指導教授 ： 周信賢(Hsin-Hsien Chou)

崑山科技大學/工程學院/環境工程研究所/碩士(2012年)

摘要

本研究除了建立UASB反應器動力模式(incorporating intrinsic kinetics)及經驗模式(incorporating apparent kinetics)外，亦使用二組UASB反應器(us = 1.0 m/h ；操作溫度= 30℃)處理低濃度糖蜜廢水以獲得實驗數據。一組UASB反應器(反應器A)採固定糖蜜基質進流濃度(COD = 500 mg/L)但陸續改變三種水力停留時間(12、6及4 h)；另一組UASB反應器(反應器B)採固定水力停留時間但改變三種有機負荷率(1.0~3.0 kg COD/m3-d)。據此，不僅可瞭解UASB反應器處理低濃度糖蜜廢水之效能及污泥顆粒特性，亦可釐清基質降解動力及質傳效應，最後以實驗數據驗證動力模式與經驗模式之適用性。
反應器A及B分別在水力停留時間12~4 h及有機負荷率1.0~3.0 kg COD/m3-d之操作條件下，不僅沒有揮發酸累積現象(COD去除率達93%以上)，且反應器內污泥顆粒化穩定、沉降性良好。此外，反應器A及B之污泥顆粒比重(1.06~1.08；1.06~1.08)及污泥顆粒平均生物密度(142900~146100 mg VSS/L；144000~145700 mg VSS/L)變化不大，但污泥顆粒平均粒徑(0.68~1.00 mm；0.64~1.31 mm)則隨有機負荷率之增加而增大。
經由批次實驗求得糖蜜基質厭氣降解intrinsic k值(0.81~0.88 mg COD/mg VSS-d)大於apparent k'值(0.70~0.78 mg COD/mg VSS-d)，intrinsic Ks值(120~130 mg COD/L)則小於apparent K's值(170~178 mg COD/L)。藉由動力模式求得之質傳參數(??2 = 3.8~16.1、Bi = 2.8~12.5及η = 0.92~0.98)得知三項訊息：(1)污泥顆粒之內部質傳阻抗明顯大於外部質傳阻抗，(2)污泥顆粒之內部質傳阻抗對整體基質去除速率之影響不大，及(3)糖蜜降解速率對整體基質去除速率之影響很大。本研究建立之動力模式及經驗模式模擬之COD去除率與UASB反應器處理低濃度糖蜜廢水實驗値之誤差在 11%範圍內，而動力模式與經驗模式模擬值之間差異百分比則僅在3.5%範圍內。

關鍵字

上流式厭氣污泥床 ； 低濃度有機廢水 ； 污泥顆粒特性 ； 質傳效應 ； 反應動力 ； 動力/經驗模式 ； 模式驗證

並列摘要

A kinetic model (incorporating intrinsic kinetics) and a homogeneous empirical model (incorporating apparent kinetics) that can be used for simulating variations in substrate residual concentration with different operating conditions in the upflow anaerobic sludge bed (UASB) reactor are formulated. Two UASB reactors (us = 1.0 m/h; operating temperature = 30℃) were also used to treat low-strength molasses wastewater to generate experimental data. One UASB reactor (reactor A) was maintained at a fixed influent COD concentration of 500 mg/L but with different hydraulic retention time (HRT = 12, 6 and 4 h) whereas the other UASB reactor (reactor B) was maintained at a fixed HRT (6 h) but with different organic loading rates (OLRs = 1.0, 2.0, and 3.0 kg COD/m3-d). Thus, not only the performance and granule characteristics of UASB reactors treating low-strength molasses wastewater can be evaluated but the associated mass transfer and reaction kinetics can also be elucidated. When the reactor A and B were respectively maintained at the HRT of 12–4 h and the OLR of 1.0–3.0 kg COD/m3-d, not only an accumulation of volatile fatty acids was not observed (above 93% of COD removal) but fairly good sludge granulation/settling can also be achieved. In addition, the granule’s specific gravity (1.06–1.08; 1.06–1.08) and the microbial density (142900–146100 mg VSSL; 144000–145700 mg VSSL) varied slightly but the average granule diameter (0.68–1.00 mm; 0.64–1.31 mm) increased with increasing OLR.
From the batch experiments, the obtained Monod kinetic parameter intrinsic k values (0.81–0.88 mg phenol/mg VSS-d) are larger than the apparent k' values (0.70–0.78 mg phenol/mg VSS-d). The intrinsic Ks values (120–130 mg phenol/L; increases with increasing OLR) are smaller than the apparent K's values (170–178 mg phenol/L). By using the validated kinetic model, the calculated mass transfer parameter values (??2 = 3.8–16.1, Bi = 2.8–12.5, ?? = 0.92–0.98) reveal three messages: (1) internal mass transfer resistance to the granule is higher than extermal mass transfer resistance, (2) the internal mass transfer rate imposes a slight effect on the overall substrate removal rate in the UASB reactors, and (3) the overall substrate removal rate is rather significantly affected by the molasses degradation rate. The calculated COD removal efficiencies using kinetic and empirical models are 11% deviated from the experimental results. The variations of the simulated results using kinetic and empirical models are within 3.5%.

並列關鍵字

upflow anaerobic sludge bed ； low-strength wastewater ； granule characteristics ； mass transfer parameters ； reaction kinetics ； kinetic/empirical model ； model validation

參考文獻

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