Disadvantages

*Trace Metals in the Environment - New Approaches and Recent Advances*

Windrows is bioremediation techniques depends on periodic rotating the piled polluted soil to improve bioremediation by increasing microbial degradation activities of native and transient hydrocarbonoclastic present in polluted soil. The periodic turning of polluted soil increase in aeration with addition of water, uniform distribution of nutrients, pollutants and microbial degradation activities, accordingly increase the rate of bioremediation, which can be proficient through acclimatization, biotransformation and mineralization. Windrow treatment as compared to biopile treatment, showed higher rate of hydrocarbon removal however, the effectiveness of the windrow for hydrocarbon removal from the soil [17]. However, periodic turning associated with windrow treatment not the best selection method to implement in bioremediation of soil polluted with toxic volatiles compounds. The use of windrow treatment has been associated in greenhouse gas (CH4) release due to formation of anaerobic zone inside piled polluted soil, which

Land farming is the simplest, outstanding bioremediation techniques due to its low cost and less equipment requirement for operation. It is mostly observed in exsitu bioremediation, while in some cases of in-situ bioremediation technique. This consideration is due to the site of treatment. Pollutant depth is important in land farming which can be carried out ex-situ or in-situ. In land farming, polluted soils are regularly excavated and tilled and site of treatment speciously regulates the type of bioremediation. When excavated polluted soil is treated on-site, it is ex-situ as it has more in common than other ex-situ bioremediation techniques. Generally, excavated polluted soils are carefully applied on a fixed layer support above the ground surface to allow aerobic biodegradation of pollutant by autochthonous microorganisms [19]. Over all, land farming bioremediation technique is very simple to design and implement, requires low capital input and can be used to treat large volume of polluted soil with minimal environmental impact and energy requirement [20].

Bioreactor is a vessel in which raw materials are converted to specific product(s) following series of biological reactions. There are different operational modes of bioreactors, which include: batch, fed-batch, sequencing batch, continuous and multistage. Bioreactor provides optimal growth conditions for bioremediation. Bioreactor filled with polluted samples for remediation process. The bioreactor based treatment of polluted soil has several advantages as compared to ex-situ bioremediation procedures. Bioreactor-based bioremediation process having excellent control of pH, temperature, agitation and aeration, substrate and inoculum concentrations efficiently reduces bioremediation time. The ability to control and manipulate process parameters in a bioreactor implies that biological reactions. The flexible nature of bioreactor designs allows maximum biological degradation while

**5.2 Windrows**

frequently reduced aeration [18].

**5.3 Land farming**

**5.4 Bioreactor**

minimizing abiotic losses [21].

Advantages of ex-situ bioremediation

• Suitable for a wide range of contaminants

• Suitability relatively simple to assess from site investigation data

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