Bioprecipitation as a Bioremediation Strategy for Environmental Cleanup 35

...Table 2.5 contd.

Method

Design

Advantages & Disadvantages

Anaerobic Baffled

Reactor (ABR)

Advantages:

- Good sludge retention times

- No biomass carrier

- High loading rates

Disadvantages:

- NA

Membrane

Bioreactor (MBR)

Advantages:

- Good biomass retention

Disadvantages:

- Fouling

* Red arrow represents gas, blue arrow represents influent and effluent, and green arrow represents recycle process.

2.4 Conclusions

Bioprecipitation offers a sustainable approach to soil and groundwater clean-up for metal(loid)

contamination. The process offers social, economic and environmental benefits as a sustainable

remediation strategy. As a biological treatment method using natural processes, public acceptance

tends to be high in comparison to a more invasive treatment, such as physical, chemical, thermal or

electrical operations.

While bioprecipitation can occur as an in-situ and ex-situ remediation technique, in-situ

treatment offers a more sustainable approach. The operation occurs at the site with minimal soil

disturbance, energy consumption and greenhouse gas emissions. The economic value is also high as

capital, maintenance and transport costs are relatively low.

Bioprecipitation can occur as an oxidative-reductive reaction or a cementation technique. The

desired mechanism of immobilization should be based on the type and degree of contamination

with a focus on chemical stability. For oxidative-reductive reactions an energy source should be

selected to facilitate the reaction. Organic waste is a viable electron donor, showing promise as a

carbon source with high COD/SO4

2– ratios for BSR. Organic waste can be repurposed to a valuable

bioprecipitation additive, enhancing the sustainable nature of the operation.

A thorough site assessment should be conducted at each site prior to implementation as a

remediation strategy. While bioprecipitation shows promise as a bioremediation strategy for

metal(loid) clean-up, laboratory testing is required to better predict its applicability for each

individual case . The strategy should be selected only if it meets the project objectives, the future land

use requirements and can achieve high removal efficacies that adhere to environmental standards.