固定生物程序結合薄膜系統處理廢污水之研究

Abstract

固定微生物處理方法(Immobilized Bio-Process, IBP)可用來去除廢污水中的有機碳(SCOD)與氨氮(NH4+-N)，本研究分別以食品工業廢水(TCOD濃度810~1,306 mg/L)與複合工業廢水(TCOD濃度279~531 mg/L)為進流水進行實驗。在EMLSS(Entrapped Mixed Liquor Suspended Solids)濃度為3,000 mg/L、5,000 mg/L及9,000 mg/L，並在12 h和24 h二種水力停留時間（HRT）之操作條件下，進行工業廢水有機碳與氨氮平均去除率研究，結果顯示IBP 提供較長的污泥停留時間 (SRT)，可較有效去除廢水中的有機碳與氨氮。食品工業廢水在IBP操作下表面去除率(Surficial Removal Rate)可達0.011~0.056 kg COD/m2-d、容積去除率(Volumetric Removal Rate)可達2.34~11.58 kg COD/m3-d，與可溶性生化需氧量去除率可達88~92%，且氨氮去除率可達87~93%；另複合工業廢水在IBP操作下表面去除率可達0.0048~0.016 kg COD/m2-d、容積去除率達1.01~3.40 kg COD /m3-d，與可溶性生化需氧量去除率可達59~80%，且氨氮去除率可達41~67%。實驗結果亦顯示雖然較低的HRT(12 h)與EMLSS濃度值(3,000 mg/L)，可溶性生化需氧量與氨氮濃度仍可有效去除，進一步說明了IBP系統具有操作簡單、較高處理效率與不需污泥迴流等條件優勢。 固定薄膜生物反應系統(Immobilized Membrane Bio-Reactor, IMBR)是由IBP系統與微濾膜(Mircofiltration, MF)所組成，並在EMLSS濃度5,000 mg/L及HRT為24 h之操作條件下，以食品工業廢水(TCOD濃度810~1,306 mg/L)進行試驗，結果顯示IMBR對SCOD去除率高達96~97%，較IBP處理方式去除率更佳，且可降低溶解性微生物產物(Soluble Microbial Products, SMP)，減緩薄膜積垢形成，並延長IMBR使用壽命。廢水經IBP處理後總SMP濃度是47 mg/L，其中包含了蛋白質(Protein) SMPP濃度是25 mg/L和碳水化合物(Carbohydrate) SMPC濃度是22 mg/L；其再經過IMBR之MF處理後出流水之SMPP和SMPC的濃度分別是22 mg/L和15 mg/L，顯見MF裝置可再去除33%碳水化合物與11%蛋白質濃度，進一步推論碳水化合物極可能在薄膜積垢濾餅層(Cake Layer)或膠體層(Gel Layer)形成中扮演一重要角色，且比蛋白質對薄膜積垢有較大的影響。IMBR另在連續和間斷過濾、曝氣和不曝氣、及以纖維(Fiber Filter, FF)前置過濾等不同操作處理條件下實驗，結果顯示FF前置過濾對於控制薄膜積垢形成有限，但間歇曝氣操作條件下可提升IMBR處理效率，且顯著地控制薄膜積垢形成。

The immobilized bioprocess (IBP) was investigated for the removal of organic carbon and ammonia nitrogen from wastewater. Two wastewaters (a food industry wastewater and a composite industrial wastewater) were investigated, one containing high concentration (810~1,306 mg/L) and the other medium concentration (279~531 mg/L) of chemical oxygen demand (TCOD). Three entrapped mixed liquor suspended solids (EMLSS) (3,000 mg/L、5,000 mg/L and 9,000 mg/L) in the IBP and two hydraulic retention times (HRT)(12 h and 24 h) were employed representing different surface loading and volume loading factors. IBP provides high sludge retention time (SRT), enabling improved removal of COD and ammonia nitrogen. The results showed 88~92% and 87~93% removals of soluble COD (SCOD) and ammonia (NH4+-N), respectively, from the food industry wastewater, when the surficial removal rate and volumetric removal rate in the IBP were 0.011~0.056 kg COD/m2-d and 2.34~11.58 kg COD/m3-d, respectively. For the composite industrial wastewater, removal of SCOD and NH4+-N were 59~80% and 41~67%, respectively, when the surficial removal rate and volumetric removal rate were 0.0048~0.016 kg COD/m2-d and 1.01~3.40 kg COD/m3-d, respectively. The results further show stable removals of COD and NH4+-N, albeit decreasing with decreasing HRT and MLSS. IBP facilitates simple operation and good effluent quality without requiring sludge recycling. The immobilized membrane bioreactor (IMBR) was investigated for the removal of organicmatter and its membrane fouling condition in treating food processing wastewater. The IMBR contains 5,000 mg/L entrapped mixed liquor suspended solids with hydraulic retention time of 24 h. The advantages of IMBR include high sludge retention time, improved removal of COD, ammonia nitrogen, and reduced membrane fouling frequency with much less production of soluble microbial products (SMPs). The results showed that the IMBR was an effective organic matter removal system because it achieved 96~97% removal of COD consistently. The concentration of total SMP in the IMBR was measured at 47mg/L which included 25 mg/L of protein and 22mg/L of carbohydrate. Steadily, approximately 33% of carbohydrate and 11% of protein were rejected by the microfiltration (MF) membrane. For this reason, it was concluded that carbohydrate poses a more significant impact on membrane fouling through formation of cake/gel layer than protein. Further, various operating conditions during membrane filtration were experimented which included continuous and intermittent filtration, aeration and non-aeration, and with fiber filter (FF) as pretreatment. It was discovered that while adding an additional FF filtration before MF might improve suspended solid retention, SMP was instead discovered to be the major cause of membrane fouling. In addition, aeration in the membrane tank could significantly improve membrane performance by scouring lightly attached particles from the membrane surface.