Permeable reactive barrier reamins the most efficient and economical option. Your views!
simply the most effective, cheapest, environmnetal friendly tech used is by air stripping. Using a blower to with a diffuser to increase the rate of air/water exchange will enhance the direct stripping and biotreatment of remaining VOC.
Ir depends on the specific case AND constraints The best soluciona can be different
Omar Algha, your response is quite impressive. But how do you compare air stripping to Permeable Reactive Barrier in terms of cost and efficiency?
The se are cases of study which can be compared using process engineering tools
Angel, your comments are highly appreciated, but please respond with more precise explanation of what technigues you consider most efficient and economical in VOC removal from groundwater.
I think there is no absolute low cost. It needs more investigations. I believe PRB might be cheap in terms of its longevity, but this still questionable as there is no real long term efficiency case studies. It also highly dependent on the construction technique and the materials being used. We are investigating a real field study using LCA and this seems to be the case of low and efficient PRB system.
It depends on the concentration. If you have high levels I think you should try an ex-situ air stripping.
To Ewa Lizpczynska- Kochany , Different compositions of Organoclay - inorgano-Organoclay and zeolite installed using soil mixing technology.
Diffused air floatation is one of the best options for VOC removal. Gas could be taken based on local availability.
The answer is a lot more complicated that the question.
Are there low permeability zone in the aquifer?
How deep the contamination?
Do you require containment?
How long do you want your system to operate? Cost?
What is the permeability of the aquifer?
What is the seepage velocity?
How large is the plume?
How old is the plume?
For deep contamination PRBs and soil mixing will not be effective, but they are great technologies for shallow contamination.
A couple of other technologies for deeper contamination are thermal (expensive), enhanced in-situ bio with bioaugmentation.
Dave, you can give the most suitable options for different pollution levels. Those are the facts the question solicits.
We have an new field-scale technology specifically designed for low-permeability contaminated zones. We call it EK-Bio. I am working with Geosyntec and Niras to field the technology. It uses Direct Current to distribute both electron donor (lactate) and Dehalococcoides microorganisms into low permeability soils with hydraulic conductivities from 10-9 to 10-5 cm/s. The electric field drives the negative charged amendments into the soil by ion migration and electro-osmosis. We completed a successful pilot test last year in Denmark and will start the full scale system in December 2012.. The contaminant is PCE. The results of the pilot study have been presented at several environmental conferences in US and EU. The target treatment zone is 3-8 meters below the surface. We just received approval for a full-scale pilot test at a US DoD site with PCE contamination in a low permeability zone that is 20-25 ft below ground surface. The best journal articles about this technology are:
Xingzhi Wu, David B. Gent, Jeffrey L. Davis, Akram N. Alshawabkeh Lactate injection by electric currents for bioremediation of tetrachloroethylene in clay, Electrochimica Acta, , Available online 22 June 2012
and
Xuhui Mao, James Wang, Ali Ciblak, Evan E. Cox, Charlotte Riis, Mads Terkelsen, David B. Gent, and Akram N. Alshawabkeh (2012), Electrokinetic-enhanced bioaugmentation for remediation of chlorinated solvents contaminated clay, Journal of Hazardous Materials, Volumes 213–214, 30 April 2012, Pages 311-317
By the way, any one with the test procedure of 4Chloroanilina and nitrobenzene part from GC MS
Electrochemical treatment is indeed an interesting technique for dense soils where (clay) particles can help transfer electrical charges and where other techniques are hindered by the low permeability of the soil. For more sandy soils, electrochemical treatment is less effective, unless additional electrolyte (salt) is added for charge conduction.
Other options for VOC removal are inserting a barrier of zero valent iron in the soil to reduce the contaminants, though ZVI will corrode (oxidize) and thus has a limited life span. Also pump and treat systems can be feasible, where pumped water can be aerated by e.g. plate aerators or tower aerators to strip the volatiles.
Your comments make a lot of sense. Certainly laboratory experiments can only be simulated in the real environment but the results may be different . Grateful for such an insightful contribution.
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