Research On Remediation Of Groundwater Contaminated By Nitrobenzene

Nitrobenzene is a kind of chemical raw material which has been applied in chemical industry market widely and which mainly aims at dyestuff, spice, agrochemical and explosive industry etc. The washes are one of the greatest pollution sources, the concentration of which reaches 2000 mg/L or so. Generally speaking, although the water quality of groundwater keeps steady, once contaminated, the treatment will be quite tough. Therefore, the contamination problem caused by nitrobenzene has been increasingly posed among the general public. At the same time, we must notice that the production of nitrobenzene is raising, the application is very extensive and correlative departments breach of duty. Consequently, the washes leak into ground, which render groundwater to be contaminated. So, it is high time to take measures to solve the problem.PRB (permeable reaction barrier) is one of in situ remediation methods, which is installed in the aquifer and in the perpendicularity of water direction. When the water runs through the PRB with the hydraulic grade, the contaminants are degraded.Heterotopic remediation is so-called drawn out to treat, which need remove contaminants to reactor. This kind of technique is approximate to surface-treatment of nitrobenzene wastewater.In this paper, the groundwater contaminated by nitrobenzene will be researched. Through the comparison of in situ and Heterotopic remediation and the analysis of running cost, the conclusion can be reached. The research content will be as follows: In the in situ remediation part, the adsorptive capacity of activated carbon is 3.72mg/g, which showed that the main role that activated carbon played is cathode and carries out prime cell reaction as a cooperation with electric field, oxido-reduction and coagulation, while the adsorption is only a super tiny part.Parameters influencing remediation effect include pH value, retention time, and ferrous-carbon ratio. Accordingly, the orthogonal experiment with three factors and three levels was designed. The result demonstrates that pH value and retention time are significant factors, while the ferrous-carbon ration is fewer significant one.Whereas the zero-valent irons rush abroad, a static experiment was performed in order to ascertain whether the effect of zero-only or the ferrous-carbon remediation would be better. The result was that the effect of the latter is 30% times better than the former, which showed that the former was only a tiny part of the latter. The other conclusion can be reached that nitrobenzene was deoxidized into aniline, and that some compounds containing iron took on great flocculation function that can adsorb much organic matters and color. In addition to these functions, the latter can destroy the phenyl further and which will be mineralized to inorganic nontoxic matters. As a result, the ferrous-carbon system was introduced to simulation model.The dynamic simulation model was designed according to such conditions that surface velocity was from 0.15 to 0.6 m/d, temperature was 10 to 16 degree centigrade, and ferrous-carbon ration was 1 to 1; which makes great success. Consequently, the concentration of nitrobenzene was far less than 5 mg/L and COD was 50mg/L or less, and the removal ratio was 98% and 93% respectively. In the Heterotopic remediation part, influence factors include ferrous-hydrogen peroxide ration, pH value, reagent dosage, reaction time, and temperature, Optimal parameter of which were 1 to 9, 3, 120mg/L ferrous, 2h, 30 degree centigrade. The verification experiment was performed, and the content of nitrobenzene was 1.80mg/L, aniline was 2.44mg/L, and COD was 57mg/L; the removal ratio of which was 97.91%, 97.58%, and 81.95%. Then, the outlet water was treated by coagulation, so each index meets the discharge standard.In short, both in situ and Heterotopic remediation gain great effect, however, some disadvantages were shown. Therefore, it's necessary to analyze the costs briefly.The economic benefit must be taken into consideration when the environmental effect meets. The advantage of in situ remediation is that once installed, rare run expense is spent. Only cost were facility investment, land construction, and material expenditure. The cost of Heterotopic method is more in spite of its excellent management. According to computation, the cost of in situ method and Heterotopic was 2.09 and 3.03 Yuan per ton water. From the context above, effective run parameters and operational experience can be obtained. In the practical work, the hydrological condition and treatment effect as well as costs should be taken into account all together to select appropriate and feasible method.