The Indoor Simulation Research On The Treatment Of PCBs In Groundwater In Situ Remediation

PCBs （Polychlorinated biphenyls） is not only a kind of persistent organic pollutants（POPs） but also one of the typical environment endocrine disruptors （EDCs）, which hasbeen widely used in heat transfer agent, lubricant, dielectric material in the transformerand capacitor, plasticizer and flame retardants,etc. PCBs exist widely in the water, soil,and the nature of animal tissue inside in the form of traces, and in many kinds of wayslike the transformer oil leaking, volatilization, dry and wet deposition and so on，it enterthe soil and groundwater, can also spread to places in the form of air. PCBs do not breakdown in soil, water or air, but carry on accumulates. PCBs exerts teratogenic,carcinogenic， mutations respectively, environmental estrogen effect, environmentaltoxicology effects in food chain and so on, strongly impair and damage biologicalendocrine system, nervous system and reproductive system, is a serious threat to thehuman survive. Although PCBs has stopped being used for many years, but already existin the environment,where great threat still exist, and carrying on the repair processing isimminent.This article take PCBs pollution of groundwater for example, combined with the PRBtechnology researches the pathway of persistent organic pollutants removal and thein-situ remediation methods and mechanism of Chemical-Biology combination-typereaction wall. In the experimental process, the PCBs migration rule in the shallowgroundwater layer was firstly carried out by a series of simulation experiment; The wallof a chemical reaction medium choice, preparation and mechanism of in-situ remediationwere secondly studied, and finally the chemical-biological sequence combination reactionwall repairing effect and influencing factors were researched. This thesis research resultsprovide some references for the future of PCBs pollution groundwater in situ remediationfield.The main conclusions of this paper give for:（1） PCBs migration rate in the groundwater level was relatively slow, in the sandlayer, groundwater flow rate was8.09cm/d, the permeability coefficient was3.16m/d, at different depths of the groundwater migration rate was different, the average rate was3.10cm/d, the retardation factor （R）=2.63, longitudinal migration trend was notobvious;（2） The experiment selected Fe and Zn combination double metal with particlesize1.0-2.0mm,10%of the amount containing zinc as the main reaction media wall ofchemical reaction;（3） In the experiment, we designed an organic glass column which had50cm long,5cm inner diameter to simulate the chemical reactions wall, and a series of indicators formonitoring like the pH value,（Eh）, PCBs （1242）, Cl^-and Fe²⁺concentration werecontented. The research showed that in the stability stage, PCBs removal rate stabled ataround80%, pH value rose and maintain in8.70, chloride ion concentration in water wasobviously higher, Fe²⁺, Zn²⁺concentration were basic stable.（4） Selected active carbon with particle size1.0-2.0mm as the carrier medium ofbiological reaction wall, combined with the PRB technology, constructed thechemical-biological combination reaction walls, simulating underground environment,removed PCBs groundwater pollution in situ remediation, in more than a monthoperation, the total PCBs removal rate reach93%.