**5. Field implementation**

Ct

where

where

Ct

= parent compound present at time t

k = zero-order reaction rate constant

C = parent compound concentration

k = first-order reaction rate constant

= parent compound present at time t

Solving for concentration yields Eq. (13):

and parameters are as defined above.

t = corresponding sampling time.

Co = initial concentration of parent compound k = first-order reaction rate constant (time−1)

t = corresponding sampling time

integration yields Eq. (12):

t = corresponding sampling time.

to its biodegradation, Eq. (11):

Co = initial concentration of parent compound

320 Soil Contamination - Current Consequences and Further Solutions

First-order reactions have rates that depend on mass transfer of parent compound concurrent

kt C Ceo

Biosurfactants may be the strategic choice for increasing contaminant bioavailability in bioreactors while minimizing toxicity to biodegraders. An examination of the literature indicates that synthetic surfactants while effective for increasing contaminant mass transfers at the recommended concentration may show inhibitorial effects on the microorganisms in the bioreactor [27, 28]. In such case, this will inhibit cell proliferation and thus the biodegradation of organic contaminants. According to empirical evidence, surfactant toxicity was found to be primarily dependent on its molecular structure, in order of toxicity, generally non-ionic <anionic < cationic [28]. Several practical approaches may be implemented to reduce surfactant

dC/dt= kC - (11)

Ln C Ln ( t o ) - = =- (C Ln ) (C /C kt t o ) (12)


First and foremost, site access should be restricted to minimize human and wildlife exposure to contamination. As a contaminated site, safety should be implemented and followed at all

**Figure 4.** Approach to main components of implementing a field bioremediation program.

time. A site assessment and site characterization program should be conducted prior to excavating and bioremediating the contaminated soil. A site characterization will involve a more rigorous and field testing program (i.e., drilling and installing groundwater monitoring wells, chemical parametrization of soil samples, soil gas sampling). A good site assessment program should provide basic and qualitative information such as how much? When? What types of contaminants was released? It should also allow to generate site-specific information pertaining to soil physical, chemical, and biological properties critical in the success of the bioremediation program. **Figure 4** provides a simplified overview of environmental site assessment approach. The site characterization should be conducted in a phased approach. Each evolutionary phase should be designed to assess the CSM. As such, this will increase the investigation capacity to perform risk analysis.

Once the areal extent of vadose contamination has been delineated and staked out, excavation can safely proceed ahead. The excavation process should be managed to prevent any additional pollution and protect the environment and human health. Common equipment used to excavate and move soils around the site includes but not limited to: a bulldozer or dozer pushes soil with a hydraulically controlled blade. A backhoe uses a toothed bucket attached to a loom or dipper stick. Front-end-loaders are tractors equipped with buckets that can be used for excavation, lifting, hauling and dumping soil material, hydraulic excavator with primary function for digging, and articulated trucks are used as versatile hauling units.

**Figure 5.** Flow diagram of a typical batch sequencing slurry bioreactor.

Several bioremediation option processes can be contemplated for on-site and off-site treatment of the excavated contaminated soil material. Irrespective of the system configuration and design, process fundamentals of a surfactant-enhanced-bioremediation efficiency requirements must be optimized prior and during project implementation. Aqueous slurry conditions typically ranging from 20 to 40% w/v are one of the most important types of *ex situ* technique [30–32]. A slurry bioreactor may consist of a vessel or a lined lagoon, which is typically run in a batch or semi-continuous operation mode. Sometimes, they may be operated in sequencing batch reactors to achieve a desired treatment train objective as illustrated in **Figure 5**. Dehalogenation under anaerobic conditions of chlorinated contaminants is initially necessary prior to aerobic treatment. When dehalogenation is not required, the treatment process can be carried out aerobically only. During treatment, slurry mixing may be performed with mechanical or pneumatic devices in a rather intermittent than continuous mode.

time. A site assessment and site characterization program should be conducted prior to excavating and bioremediating the contaminated soil. A site characterization will involve a more rigorous and field testing program (i.e., drilling and installing groundwater monitoring wells, chemical parametrization of soil samples, soil gas sampling). A good site assessment program should provide basic and qualitative information such as how much? When? What types of contaminants was released? It should also allow to generate site-specific information pertaining to soil physical, chemical, and biological properties critical in the success of the bioremediation program. **Figure 4** provides a simplified overview of environmental site assessment approach. The site characterization should be conducted in a phased approach. Each evolutionary phase should be designed to assess the CSM. As such, this will increase the

Once the areal extent of vadose contamination has been delineated and staked out, excavation can safely proceed ahead. The excavation process should be managed to prevent any additional pollution and protect the environment and human health. Common equipment used to excavate and move soils around the site includes but not limited to: a bulldozer or dozer pushes soil with a hydraulically controlled blade. A backhoe uses a toothed bucket attached to a loom or dipper stick. Front-end-loaders are tractors equipped with buckets that can be used for excavation, lifting, hauling and dumping soil material, hydraulic excavator with primary

Several bioremediation option processes can be contemplated for on-site and off-site treatment of the excavated contaminated soil material. Irrespective of the system configuration and design, process fundamentals of a surfactant-enhanced-bioremediation efficiency requirements must be optimized prior and during project implementation. Aqueous slurry conditions typically ranging from 20 to 40% w/v are one of the most important types of *ex situ* technique [30–32]. A slurry bioreactor may consist of a vessel or a lined lagoon, which is typically run in

function for digging, and articulated trucks are used as versatile hauling units.

investigation capacity to perform risk analysis.

322 Soil Contamination - Current Consequences and Further Solutions

**Figure 5.** Flow diagram of a typical batch sequencing slurry bioreactor.


**Table 5.** Matrix of CSF for *ex situ* surfactant enhanced bioremediation.

Mixing will play a critical role by increasing mass transfer rates and bioavailability of contaminants as enhanced by the presence of surfactant, provide slurry homogenization, keep solid particles in suspension, and help achieving oxygen transfer in aerobic bioreactor. In its simple design, a SB construction will consist of soil handling and conditioning area, aeration device, the bioreactor (anaerobic/aerobic) itself, drying and storage area of treated material, off-gas treatment, and chemical storage area. Air quality monitoring should be conducted at and around the site.

A matrix summary of critical success factors (CSFs) for *ex situ* surfactant enhanced bioremediation has been best summarized in **Table 5**.
