河流渗滤系统中苯系物污染去除机理实验模拟研究

EXPERIMENTAL SIMULATION STUDY OF REMOVAL MECHANISM OF BTEX IN RIVER FILTRATION SYSTEM

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。通过静态吸附实验和淋滤实验模拟了苯系物(BTEX)在河流渗滤系统中的吸附行为和降解行为。两种环境行为中吸附作用对于BTEX的净化效果较为有限,当吸附达到饱和之后,并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,其次是乙苯、甲苯,去除率最差的是苯。微生物降解作用相对于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,在两种电子受体的情况下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情况下,去除效率会大大降低,从而使BTEX穿透包气带进入含水层,对地下水产生危害。

River filtration system is a natural purification.It means that during 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 action.Multiple analogue experiments including soil test and static adsorption experiments were applied in this study in order to reveal the environmental behaviors and removal mechanism of BTEX（benzene,toluene,ethylbenzene and xylene）in the river filtration system.Adsorption and microbial degradation were the primary environmental behaviors of BTEX in the river filtration system.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,M-xylene was the highest,the second was Toluene and Ethyl-benzene,and that of Benzene was the lowest.The stability of the structure of Benzene determined its relatively lower degradation efficiency,and the low removal ratio of Toluene was due to the effect of adsorption on degradation.The soil-water partition coefficient Kd of each component of BTEX was higher,the degradation ratio was lower.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 unsaturated zone and threaten the security of the ground water.