胞外聚合物對生物重金屬溶出程序之影響

Abstract

因微生物胞外聚合物 (Extracellular Polymeric Substance, EPS) 在生物處理程序中可促進微生物群體之膠凝作用，進而形成顆粒化污泥或附著性生物膜，有助於微生物總量之增加和多元化菌種之截流，以達廢水中污染物之徹底分解。而由於 EPS 在生物溶出法中主要三大機制: (1) 保護作用、(2) 吸附作用及(3) 酵素作用。所以可見 EPS對於生物溶出法具有一定的影響力。 以實驗設計的規劃為二因子 (X1= 固體物濃度、X2= 硫片添加量) 的中央合成設計，而每個獨立因子變數分別具有 5 個水準範圍，固體物濃度 (X1) 從 0.5% 至 5.0% (w/w)；硫粉添加量 (X2) 則是從0.5% 至 4.0% (w/w)。而根據實驗設計並以氣提示反應槽來進行反應所得到的結果如下: pH: 1.15-5.82；EPS 產生量: 210-4300 mg/L；硫酸根濃度: 5540-28300 mg/L；懸浮固體物去除率: 30-65%；揮發性懸浮固體物去除率: 15-62%；銅溶出率: 23-98%；鎘溶出率: 23-98%；鉻溶出率: 11-91%；鉛溶出率: 17-52%；鋅溶出率: 42-99%；鎳溶出率: 54-98%；錳溶出率: 24-99%。由反應曲面及等高線圖可知，只要將固體物濃度控制在 0.5-1.5% 且硫片添加量在0.5-2.0% 之間時，重金屬溶出率即可達到 95% 以上。由 AFM 及SEM 觀察可有效證實胞外聚合物之吸附及酵素作用，故 EPS 對污泥重金屬溶出程序確實具有一定的影響作用。pH 除了對重金屬溶出效率和硫酸鹽產率有一定的影響之外，對於微生物群體及 EPS 的產生也會有相當影響，所以 pH 值對於生物溶出法為一非常重要的因子。

Because Extracellular Polymeric Substances (EPS) promote bacterial be adhesive biofilm and agglomerates. By mean of bioflocculation, it will raise bacterial population and increase capability of decompose pollutants. EPS are having three major functions in bioleaching such as adsorption, protection and catalysis on bioleaching process. Using the experimental design method to plan Central Compose Design of two factors (X1= sludge concentration; X2= sulfur addition). The result is: pH: 1.15-5.82; yield of EPS: 210-4300 mg/L; concentration of SO42-: 5540-28300 mg/L; SS removal ratio: 30-65%; VSS removal ratio: 15-62%; Cu solubilization: 23-98%; Cd solubilization: 23-98%; Cr solubilization: 11-91%; Pb solubilization: 17-52%; Zn solubilization: 42-99%; Ni solubilization: 54-98%; Mn solubilization: 24-99%. AFM and SEM imaged EPS include adsorption and catalysis. EPS can reduce processing period and upgrade processing efficiency for removing heavy metals from sludge. The EPS production has increased with TS increased. However, it has a clear pick at 10-16 days. It is mean that when solution have a large number of H+ and SO42- and metal ions it will let bacterial product large EPS. Consequently, heavy metals solubilization and EPS production have effected by pH. So pH value will be a very important factor on bioleachinig process.