以分子大小排斥層析法分析水中溶解態有機物

Abstract

本論文以分子大小排斥層析法 (size exclusion chromatography, SEC) 對溶解態有機物 (dissolved organic matter, DOM) 進行研究，內容可分為四個部份：第一部份以牛血清蛋白 (bovine serum albumin, BSA) 和腐植酸 (humic acid, HA) 為天然有機物模型，以親和層析樹脂後面接離子樹脂對有機物分級，配合分子量分佈、溶解態有機碳 (dissolved organic carbon, DOC) 和螢光激發-放射圖譜 (excitation-emission matrix, EEM) 分析每個部分的有機物性質。BSA 和 HA 單獨測試，主要為疏水中性物質 (HPON) 和疏水酸性物質 (HPOA)，疏水部份平均佔 85%； BSA-HA 混和物測試，疏水部份分別只有 71.7% 和 60.9%，漏出的部分為親水鹼性物質 (HPIB)，顯示 BSA 和 HA的交互影響下，疏水性和酸性都減弱。 第二部份以 SEC 分級和樹脂分級研究原水有機物性質，在原水中 DOM 分子量在 1200 – 10,000 Da 五種有機物，螢光特徵皆纇似腐植酸和蛋白質類物質，且大部份的有機物為疏水物質。以分子量分佈和 EEM 觀察長興淨水廠程序水和原水，以聚氯化鋁 (Polyaluminum Chloride, PACl) 混凝加藥及活性碳吸附移除 DOM，水廠程序只能移除部份大分子，且對 DOC 移除貢獻很少。PACl 能移除大分子量的有機物，對小分子無任何效果，活性碳則能完全吸附螢光物質。

第三部份是將不同填埋齡和生物處理程序的滲濾液，以 SEC 進行分子量分級，配合DOC、UV254、折射率 (refractive index, RI)和 EEM 測量。新鮮滲濾液 S1 主要是分子量 1800-300 Da 的碳水化合物和蛋白質，佔總 DOC 的 85.2%，在填埋齡達 3-7年可降解99%，殘留部分為螢光物質。小於300 Da分子佔 S1 11% DOC，具有很強的螢光和些許 RI 訊號，但沒有 UV254 吸收，長時間填埋可降解 91%。大於 1800 Da分子在 S1 雖只佔少量，但有很強的 UV254和螢光，填埋齡 1 – 2 年可降解 44%，更長的填埋齡並不能有效移除。厭氧和好氧處理程序可有效移除小分子 (< 300 Da)，大分子 (> 10,000 Da) 只能降解成較小的分子 (2000 – 10,000 Da)。由螢光 EEM 顯示，滲濾液的蛋白質類和腐植質類有機物，隨著長時間填埋和厭氧、好氧生物處理而增加。 第四部份亦使用SEC技術，將酚培養的好氧生物顆粒填充於管柱內，以分子量標準品PEG 200 – 20000為探源 (tracer)，偵測生物顆粒內部的孔隙度，生物顆粒直徑0.46 mm、1.08 mm和 1.28 mm對應的排斥極限為139,000 Da、123,000 Da 和 54,500 Da，顯示小的生物顆粒有較開放的結構。測得的沖提曲線配合對流分散模型和雙重孔隙介質，可得到探源於生物顆粒內部的分散係數。有效孔隙度和 Pe數隨分子量和生物顆粒尺寸增加而減小。越大的分子有較低的內外滲透性比 (內外速率比)，滲透性比高的生物顆粒，生物活性沒有比較高，對應的通過時間也比較長，因此孔隙度反映的可能只是生物活性的部份因素。

This thesis reported the characteristics of dissolved organic matters using size exclusion chromatography (SEC). First work adopted IHSS humic acid (HA) and bovine serum albumin (BSA) as the model NOM. For HA and BSA alone tests, major fraction was consist of hydrophobic acid (HPOA) and hydrophobic netural (HPON), and the hydrophobic compounds contributed 85% of total DOC on average, while the two BSA-HA mixture tests were only 71.7% and 60.9% in hydrophobic part respectively. The leakage part was collected as hydrophilic base by a cation exchange resin. Hence, the interplay of HA and BSA exhibits reduced hydrophobicity and reduced acidity. Second, the DOM in raw water from Chang-Hsing treatment plant was characterized by SEC and resin fractionation and measurements as the previous description. Five peaks between 1200-10,000 Da were related to the same humic-like and protein-like fluorescent compound, and most DOM were absorbed as hydrophobic fraction by DAX-8 resin. The DOM removal by treatment train showed no significant difference in DOC and reduced only part of high molecules. For coagulation-flocculation tests, high MW DOM can be gradually removed with increasing PAC dosing probably because of forming electrostatic patch and sweep, but no effects for small molecules. For activated carbon treatment, most of fluorescent compound can be adsorbed. Third, the leachate samples from different landfill age and bio-treatment were fractionated in molecular weight (MW) using size exclusion chromatography coupling with DOC, UV254, RI and EEM measurement. The leachate from fresh waste had DOC of 19900 mgL-1, with 85.2% of which being carbohydrates and alike with some aromatic proteins of MW 300-1800 Da. Over 99% of this fraction of DOM was degraded following 3-7 years of landfill, leaving those with fluorescent activity. The DOM in leachate from fresh waste of MW<300 Da, accounting for 11% of DOC in S1 and having strong EEM intensities, certain RI but no UV254 absorbance, could be degraded by 91% in landfill up to seven years. The DOM in leachate from fresh waste of MW>1800 Da, having low DOC content, strong UV254 absorbance and strong EEM peaks, could be degraded by near 44% in landfill in the first 1-2 years. Further landfilling could not effectively remove this fraction of DOM. Anaerobic or aerobic treatment of landfill leachate could degrade DOM of MW<300 Da, and transformed those with fluorescent activities of MW>105 Da to those of 2000-105 Da. The aromatic proteins and humic substances were enriched in landfill leachate along with landfill age and with anaerobic/aerobic treatments. Fourth, the elution of polyethylene glycols (PEG) of molecular weight 200-20000 from aerobic granules were experimentally evaluated, from which the pore size distribution characterized with PEG molecular weights and the corresponding internal permeability of phenol-fed, aerobic granules were estimated with the help of one-dimensional convection-dispersion model and double porosity model. The exclusion limits in terms of molecular weight are 139,000 Da, 123,000 Da, and 54,500 Da, for 0.46 mm, 1.08 mm, and 1.28 mm granules, respectively. The available porosity and Peclet number decreased with increase in molecular weight of the molecules and granule size. The granule with high permeability ratio can’t guarantee high bio-activity while with long transit time. Therefore, the porosity only reflect part of bio-activity.