碱性缺氧环境下地下水中苯和甲苯的生物降解

BIODEGRADATION OF BENZENE AND TOLUENE IN GROUNDWATER UNDER AN ALKALINE AND ANOXIC CONDITION

在缺氧环境下,不额外加入电子受体和营养盐,从长期受原油污染的包气带介质中分离、培养驯化得到了降解苯或甲苯的3种优势菌群:B-bacteria、T-bacteria和M-bacteria,采用批试验方法研究了高pH环境下3种菌群降解苯和甲苯的速率。结果表明:苯和甲苯的降解符合零级反应动力学,速率常数在0.22～0.68 mg/(L.d)。初始pH从8.7升高到9.6和10.6时,B-bacteria降解苯的速率降低都在10%以内;T-bacteria降解甲苯的速率降低率从pH9.6时的16.22%剧增到pH10.6时的41.23%;而M-bacteria降解苯和甲苯的速率降低从pH9.6时的30%左右增到pH10.6时的45%左右。高pH环境下微生物仍能完全降解苯和甲苯。故设计化学-生物连续反应格栅治理该类污染羽时,在两个单元中间可不构筑pH调节缓冲单元。

Three predominated classes of microbes,B-bacteria,T-bacteria and M-bacteria,were inoculated from soils which were collected from a vadose zone chronically contaminated by cruel oil,fed with benzene and toluene and cultured without extra nutrients and electron acceptors under anoxic conditions.Laboratory batch studies were performed to assess the potential for biodegradation of benzene and toluene at high pH levels.The results showed that the degradation processes fit zero-order kinetics equations well and the rate constants ranged from 0.22 to 0.68 mg/（L·d）.The rates of benzene and toluene biodegradation by the three cultures decreased variously when increasing the initial pH values from 8.7 to 9.6 and 10.6,respectively.The rates of benzene biodegradation by B-bacteria were reduced by less than 10%;the rates of toluene biodegradation by T-bacteria were decreased from 16.22% at the initial pH 9.6 to 41.23% at the initial pH 10.6;and the rates of benzene and toluene biodegradation by M-bacteria were decreased from about 30% at the initial pH 9.6 to about 45% at the initial pH 10.6.Benzene and toluene could be thoroughly biodegraded even at pH 10.6.It is recommended that no extra pH buffer zone between an Fe0-PRB and a bio-wall should be necessary for designing sequential PRBs to treat such pollutants in aquifers.