以厭氧耐鹽菌處理酸菜廢水

Abstract

酸菜廢水中含有高濃度的鹽分以及有機質，若直接排放會造成嚴重的環境汚染，為解決此問題，本研究以馴化過的海水養蝦池厭氧汙泥處理此高鹽分的酸菜廢水。開始時先以人工廢水馴養厭氧汙泥，以逐步提高鹽度的方式，使菌種對高鹽度產生適應性。接著分別使用5%、7%與10%鹽度的人工廢水與稀釋至鹽度為6%與9%的酸菜廢水進行測試，測試時分別以HRT5天及10天進行操作。 當反應槽進流10%鹽度的人工廢水，在HRT為10天，有機負荷率(organic loading rate, OLR)為4 g COD/L/day的操作條件下，經24天的培養，發現pH從7.25下降至5.04，COD去除率從95.3%下降至64.6%，顯示過高的鹽度下假如不調整反應槽的pH，甲烷菌會受到抑制。 而稀釋酸菜廢水的試驗中，HRT依序操作在10天和5天，OLR分別為0.64 g COD/L/day與1.24 g COD/L/day。當鹽度為6%，HRT為10天時，可達到72%的COD去除率，氣體產率(gas production rate, GPR)與甲烷產率(methane production rate, MPR)分別為0.15 L/L/day與0.09 L CH4/L/day；HRT為5天時，相同的6%鹽度酸菜廢水則可達到75%的COD去除率，並且GPR與MPR分別為0.38 L/L/day與0.21 L CH4/L/day。顯示在6%的鹽度下，增加OLR對GPR與MPR有提升的效果，GPR與MPR在HRT 5天時分別為HRT 10天的3.17倍與2.73倍。 當進流酸菜廢水之鹽度提高至9%，HRT為10天時，OLR增加至0.85 g COD/L/day，GPR與MPR也上升至0.28 L/L/day與0.19 L CH4/L/day，平均COD去除率為78%，甲烷含量為72%，顯示在HRT為10天之條件下，鹽度即使達到9%，對甲烷菌抑制並不明顯。但是當HRT為5天時， pH會呈現持續下降，最後降至5.18，而COD去除率也降至18%。產氣同時也受到影響，GPR降至0.26 L/L/day，MPR降至0.10 L CH4/L/day，甲烷含量則為40%。因此在處理較高鹽度的廢水時，厭氧反應槽須操作在較大的HRT即較低的有機負荷。綜合言之，本研究成功地以馴養過的厭氧汙泥處理酸菜廢水並產生可燃燒的甲烷，對於處理酸菜廢水提供了新的解決方式，。

Pickled mustard wastewater must be treated prior to discharge or it will severely pollute the environment because of its high salinity and organic contents. To solve this problem, this study proposed using the acclimated anaerobic sludge from the seawater shrimp pond to treat this saline wastewater. In the beginning, the anaerobic sludge was acclimated using the synthetic wastewater and through gradually step-increasing salt contents, these anaerobic bacteria were able to adapt to the saline environment. After acclimation, different tests of using 5, 7 and 10% of synthetic saline wastewater, and 6 and 9% of dilute pickled mustard wastewater were conducted. Both types of wastewater were operated at HRTs of 5 days and 10 days. When fed with 10% salt of synthetic wastewater, and operated at 10 days HRT and 4 g COD/L/day of organic loading rate, the performance results showed that pH dropped from 7.25 to 5.04 and COD removal efficiency was decreasing from 95.3% to 64.6% after 24 days. It indicated that the growth of anaerobic bacteria would be inhibited if the pH was not adjusted suitably for the high salt content wastewater. For tests of feeding dilute pickled mustard wastewater, the HRT were sequentially operated at 10 and 5 days with the OLR of 0.64 and 1.24 g COD/L/day, respectively. In test of 6% salt wastewater and 10 days HRT, 72% of the COD removal efficiency, and 0.15 L/L/day of GPR (gas production rate) and 0.09 L CH4/L/day of MPR (methane production rate) were achieved. With the same 6% salt wastewater, in test of 5 days HRT, a better performance results of 75% of the COD removal efficiency, and 0.38 L/L/day of GPR (gas production rate) and 0.21 L CH4/L/day of MPR (methane production rate) were achieved. It clearly indicated that, at 6% salt content, increasing OLR will improve the gas production GPR and MPR effectively. Comparing the results of HRT 5 days and 10 days, GPR and MPR were lifted up to 3.17 and 2.73 times, respectively. When feeding 9% salt content of dilute pickled mustard wastewater, in test of 10 days HRT, the OLR was increasing to 0.85 g COD/L/day. Both GPR and MPR were increasing to 0.28 L/L/day and 0.19 L CH4/L/day, respectively, and 78% of the average COD removal efficiency and 72% of methane content were achieved. It showed that no indication of inhibiting the anaerobic bacteria under the condition of 10 days HRT and 9% of salt content. However, in test of 5 days HRT with the same 9% salt content, the pH kept on decreasing to 5.18 and the COD removal efficiency was decreasing to only 18%. The gas production was affected either, both GPR and MPR were decreasing to 0.26 L/L/day and 0.10 L CH4/L/day, respectively, and the methane content was decreasing to 40%. Therefore, in treatment of the high salt content wastewater, the anaerobic reactor should be operated at a longer HRT, i.e., a lower OLR. In summary, this study provides a new method by using the acclimated anaerobic sludge treated the pickled mustard wastewater and produced the combustible methane gas successfully.