Electrokinetic Biofences

Number of charged particles caught by the fence Number of charged particles entering the fence area 

Cb = concentration in front of the fence (iUg/1), and Ce = concentration behind the fence 

Electrochemical Remediation Technologies for Polluted Soils, Sediments and Groundwater, Edited by Krishna R. Reddy and Claudio Cameselle Copyright 2009 John Wiley Sons, Inc. 

The yield can be determined by computer simulations that calculate the velocity of the charged particles coming toward the fence for each value of the relevant physical/chemical and geohydrological parameters. Important parameters in this respect are Usted in Table 17.1. 

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Electrokinetic biobarriers (also known as electrokinetic biofences) are modified electrokinetic barrier used to contain and biodegrade organic pollutants in ground-... 

Depending on site-specific circumstances, an electrokinetic biofence is set up according to the following configuration A row of alternating anode and cathode... 

At the site of chemical laundry, a project with an electrokinetic biofence (EBIS ) started in April 2001. This fence has been installed to disperse nutrients in the ground and groundwater in order to enhance reductive dechlorinization of present perchloroethene (PCE), trichloroethene (TCE), cw-l,2-dichloroethene (C-DCE),... 

Figure 17.2. Schematic representation of an electrokinetic biofence. The enhancement of biodegradation inside and downstream of the fence area was by inducement of nutrients and homogeneous dispersion of nutrients.

The electrokinetic biofence consists of three cathodes and two anodes. The electrode wells have been placed in a row at a mutual distance of 5 m, downstream of the chemical laundry up to 10 m depth. At a distance of approximately 2 m upstream of the electrode wells, 24 infiltration wells have been installed, 19 of which are in use so far. These infiltration filters consist of polyethylene (PE) filter tubes with a diameter of 50 mm, length of 10 m, and perforation from 1 to lOmbgs. Each filter can be filled with approximately 13 kg of solid nutrients, consisting of sodium, calcium, nitrogen, phosphorus, and ammonium compounds. 

Table 17.2 indicates that sufficient nutrients in the form of a carbon source (DOC), nitrogen (N-Kjeldahl), and phosphorus are present in the groundwater.The concentration of nitrogen increased with nearly a factor 10 during measurement in July 2003 and decreased to a concentration of about 6mg/l at the end of last year. Phosphate increased 5 times in July 2003 and 15 times at the end of 2005. The concentration of DOC first increased with a factor 2 but decreased in the last period to 52mg/l. It cannot be derived from the determination of DOC whether all present carbon forms a suitable source for the decomposition of VOCs. Experience and data from literature indicate that the nutrients, administered through the electrode wells and infiltration filters, are quickly decomposed and that they have a positive influence on the decomposition process of VOCs. The data show clearly that the concentration of these nutrients and electron donors increases, caused by the infiltration and dispersion of nutrients by the electrokinetic biofence. 

VOCs An electrokinetic biofence is designed to remove VOCs in a groundwater plume or to stop their downstream migration. The biofence will stimulate and create optimal conditions for biological activity to dechlorinate VOCs downstream of the fence. In Figures 17.6 and 17.7, the development in concentrations of PCE + TCE and C-DCE + VC is represented. Note that the building of the chemical laundry starts just 1 m south of the nutrient infiltration. 

Godschalk MS, Lageman R. (2005). Electrokinetic biofence, remediation of VOCs with solar energy and bacteria. Engineering Geology 77(3-4) 225-231. 

Electrokinetic Biofence (EBF). Besides the chain of electrodes, a row of filters with nutrients is placed upstream of the electrodes. Groundwater transports the dissolved nutrients toward the electrodes. Under the influence of the electrical field, the electrically charged nutrients are dispersed homogeneously between the electrodes, enhancing biodegradation (see Chapter 22). 

Lageman R, Pool W (2009) Electrokinetic biofences. In Reddy KR, Cameselle C (eds) Electrochemical remediation technologies for polluted soils, sediments and groundwater. Wiley, Hoboken, pp 357-366... 

Electrokinetic biofence (EBF) consists of a row of alternating cathodes and anodes with a mutual distance of 5 m. Upstream of the line of electrodes, a series of infiltration wells were installed, which have been periodically filled with nutrients. The aim of the EBF is to enhance biodegradation of the VOCs in the groundwater at the zone of the fence by electrokinetic dispersion of the dissolved nutrients in the groundwater. After running the EBF for nearly 2 years, clear results have been observed. The concentration of nutrients in the zone has increased, the chloride index is decreasing, and VOCs are being dechlorinated by bioactivity. 

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