BTEX在河流渗滤系统中的降解行为实验模拟研究

河流渗滤是一种自然净化过程,污染河水通过该过程在河流沉积层中发生各种物理、化学和生物作用,使得污染物浓度降低,河水水质得到净化,从而达到增加地下水开采量的目的。本项研究通过淋滤实验,利用自行设计的土柱实验装置和人工配制的淋滤液,模拟了BTEX污染河水在下渗通过河流渗滤系统的过程中发生的降解行为。实验历时48 d,获得了该过程中BTEX各组分和电子受体的质量浓度变化历时曲线,得出的结论包括：污染河水中的BTEX在通过河流渗滤系统时将发生两种环境行为—吸附和降解。其中,吸附作用对于BTEX的净化效果较为有限,当吸附达到饱和之后,在存在电子受体的情况下,BTEX能够发生厌氧微生物降解,降解作用能够更有效的去除BTEX污染物。其中去除效率最高的是间二甲苯,在以NO3-为电子受体的情况下平均去除率为85.5%,在以SO42-为电子受体的情况下平均去除率为82.4%,其次是乙苯、甲苯,去除率最差的是苯,在两种电子受体的系统中平均去除率分别为68.5%和63.5%。由于吸附作用的影响,微生物降解相对于BTEX浓度变化存在一个滞后期,BTEX各组分的土壤-水吸附分配系数Kd越大,总的降解效率也就越低。通过河流渗滤系统这一自然净化过程,可以有效地去除浓度较高的BTEX混合污染,各组分平均去除效率都超过了60%,最高去除率均超过了80%。对于持续不断入渗的污染河水,当土壤吸附达到饱和、微生物活性受到抑制,去除效率会大大降低,从而使BTEX穿透河流沉积层进入含水层,对地下水产生危害。

Experimental simulation study of microbial degradation of BTEX in the river filtration system

River filtration system is a natural purification,which means while the river water passing through the soil and the aquifer material,potential contaminants in the river water are filtered and attenuated by a series of physical,chemical and biological actions.In this study soil column experiments were carried out with self-designed experimental device and artificial leachate to simulate the degradation of BTEX during the process of the polluted river water passing through the river filtration system.The experiment duration was 48d,and the duration curves of the four components of BTEX and two electron acceptors were obtained.The results revealed that environmental behaviors of BTEX in the river filtration system were including adsorption and microbial degradation.The purification effect of adsorption was limited.On the other hand,BTEX contamination could be well removed by degradation.Among the removal ratios of the four components of BTEX,that of M-xylene was the highest,the average removal ratios of which under the conditions of the two different electron acceptors NO3-and SO42-were respectively 85.5% and 82.4%,the second was Toluene and Ethyl-benzene,and that of Benzene was the lowest,which reached 68.5% and 63.5%.The degradation of BTEX lagged behind the changing of the concentration of BTEX due to the effect of the adsorption.The soil-water partition coefficient Kdof each component of BTEX was the higher,the degradation ratio was the lower.The results showed that all of the best removal ratios of the four components of BTEX were over 80% and the average removal ratios were also over 60%.As a natural purification river filtration could efficiently remove the BTEX mixed pollution within a quite high concentration range and protect the ground water from being contaminated,but its purification effect was limited within a certain range of time and concentration.When the adsorption saturation was achieved and microbial activity was restrained,BTEX contamination would penetrate through the riverbed sediments and threaten the security of the ground water.