開發臭味與水溶性有機廢氣減除之生物反應系統

Abstract

本研究利用實驗室篩選之有效除臭菌植種於反應器，針對堆肥場臭味與科技業所產生之水溶性有機廢氣進行減除試驗。

常見於堆肥場所產生之臭味物質包括含氮化合物 (氨氣、有機胺化合物)、含硫化合物 (硫化氫、有機硫化合物) 和短鏈脂肪酸 (C2-C6) 等。第一部份研究以先前實驗室及模場研究成果為基礎，選定大型堆肥場，設計並建置一座將實驗室規模放大 2,800倍之實場模組化生物除臭系統，其設計操作處理風量可達 34 m3 min-1。經實場長時間操作驗證，結果顯示本系統對96 ppm氨氣去除率可達 97%，220 ppm有機胺去除率可達 98%，其他低濃度 (< 10 ppm) 臭味物質則可完全去除。操作參數顯示本系統可長時間操作保持其去除效能，特別是低壓損 (< 45 mmH2O m-1) 之結果表示系統內無堵塞現象，毋須經常更換反應器之濾料或進行翻堆。菌數、二氧化碳及代謝物分析顯示堆肥場臭味物質確實由系統內微生物所分解代謝，轉化為硝酸根離子，循環水可進行濃縮處理，調整成份成為適合液態肥料。此外，本系統採模組化設計，可用適當工作體積應用於各種場所產生之臭味。

國內半導體與光電業排放水溶性揮發有機廢氣以丙酮及異丙醇為最大宗。在先導研究中，氣體滯留時間30秒，對100 ppm 丙酮與異丙醇單獨進流與混合進流氣體，去除效率皆可達到99% 以上。本研究第二部份將已篩得對水溶性揮發有機物具高去除能力之菌株植種至三種實驗室規模生物反應系統 (生物濾床、流體化生物洗滌塔、改良式平板生物洗滌塔) 分別進行降解試驗。結果顯示，生物濾床與改良式平板生物洗滌塔在所有操作條件下，對丙酮與異丙醇去除效率皆可達 90% 以上，而流體化生物洗滌塔對丙酮高進流負荷 (氣體滯留時間10秒，進流濃度300-800 ppm) 條件下去除效率能達到 80-90%。進一步分別在半導體廠與光電廠設置模場規模生物除臭系統進行降解試驗，本研究因考慮去除效率及放大成本而採用流體化生物洗滌塔，模場驗證顯示在操作30-180 天期間，所採用之反應器設計與植種菌株能使得去除效率穩定維持在90% 以上，與實驗室規模降解試驗一致。

綜合以上實驗結果，可知本研究對堆肥場綜合臭味具有實場實效，模組化設計可因應各種臭味來源選擇固定化菌株，有效確保生物除臭系統效能。此外，改良式平板生物洗滌塔之去除效率接近生物濾床，代表改良式平板生物洗滌塔中填充管柱之液氣接觸通道設計得當，有助於提昇生物反應系統效能，其輕量化設計具有商品化潛力。而模場測試確認菌株能有效降解水溶性有機廢氣，未來可搭配反應器設計提昇除臭效能。

This study used a bioreactor system with several effective strains, which were screened by our laboratory, for degradation of odors and water-soluble organic waste gases emitted from composting facilities and electronic industries, respectively.

Some odorous substances are commonly found in composting facilities including nitrogen-containing compounds (ammonia, amines), sulfur-containing compounds (hydrogen sulfide, organic sulfur compounds) and short-chain fatty-acids (C2-C6). The first part of this study was based on previous laboratory- and pilot-scale studies of our group. We designed and established a large-scale modular bioreactor system which was 2,800 fold scaled-up from laboratory-scale in a big composting facility. The flow rate can achieve 34 CMM (cube meters per minute). During a long term operation period, this modular bioreactor system has been proven effective in eliminating odors, with a 97% removal efficiency for 96 ppm ammonia, a 98% removal efficiency for 220 ppm amines, and a 100% removal efficiency of other odorous substances, respectively. The monitoring of operation parameters indicated that this system was stable during a long term operational period. Specially, a low pressure drop (< 45 mmH2O m-1) was observed, indicating that the packing carrier in bioreactor units does not require frequent replacement. The monitoring of bacterial count, carbon dioxide concentrations, and nitrogen-containing metabolites showed that the odorous substances were certainly degraded by the strains and transformed to nitrate. Moreover, the recirculated water can be used as liquid fertilizer. Thus, this modular bioreactor system can be used in field applications to eliminate various odors with compact working volume.

The widespread of acetone and isopropanol (IPA) emitted from semiconductor and optoelectronics industries release tens of thousand tons into the environment. In our preliminary studies, the removal efficiencies of 100 ppm acetone and IPA, either individual or mixed inlet, within a gas retention time (GRT) 30 seconds can achieve 99%. Therefore, the second part of this study inoculated some effective strains in three laboratory-scale bioreactor systems (biofilter, bioscrubber, modified column packed bioreactor) for elimination evaluation. The results showed that the removal efficiencies of acetone and IPA can achieve over 90% within all operational conditions by the biofilter and the modified column packed bioreactor. However, the removal efficiencies of acetone within high inlet loading (GRT 10 seconds, inlet concentration 300-800 ppm) achieved 80% to 90% by the bioscrubber. The bioscrubber type was considered for further pilot-scale test because of the removal efficiencies and cost consideration. Two pilot-scale bioscrubbers packed with raschigs established in a semiconductor and an optoelectronics factory, respectively. The results showed that the proper reactor design and the effective strains used in this study provided a stable removal efficiency of acetone over 90% within a 30-180 days period.

To sum up, the large-scale bioreactor system was effective in odors elimination of composting facilities. The modular reactor units design with proper strains is feasible for various odor components, which can provide operational stability. Besides, the similar removal efficiencies between the laboratory-scale column packed bioreactor and the biofilter indicated that the proper design of liquid-gas contact channel within modified column can elevate the system effectiveness. Eventually, the results of pilot-scale application showed that the inoculated strains can eliminate acetone effectively, and the bioscrubber can be used with a proper reactor design in the future.