Question

Which of the following is an example of in-situ bioremediation?

• A. Pumping contaminated groundwater to the surface for treatment
• B. Excavating contaminated soil and treating it in a bioreactor
• C. Injecting microorganisms directly into the contaminated site
• D. Spraying chemical agents onto polluted surfaces

Hint:

• In-situ bioremediation Treatment occurs at the contaminated site itself (e.g., bioventing, biosparging, bioaugmentation by injection). Latin "in situ" means "in the original place."
• Ex-situ bioremediation Contaminated material is excavated/removed and treated elsewhere (e.g., landfarming, biopiles, bioreactors). Latin "ex situ" means "out of place."

Answer 1

The Correct Option is C

Bioremediation techniques can be broadly classified as in-situ or ex-situ:

• In-situ Bioremediation: Involves treating the contaminated material (soil, groundwater) at its original location, without excavation or removal. This often involves stimulating the activity of indigenous microorganisms or introducing specialized microbes directly into the contaminated zone.
• Ex-situ Bioremediation: Involves removing the contaminated material from its original location and treating it elsewhere, e.g., in bioreactors, landfarms, or biopiles.

Let's analyze the options:
(a) "Pumping contaminated groundwater to the surface for treatment": This is an ex-situ method (specifically, "pump-and-treat"). The water is removed from its site for treatment.
(b) "Excavating contaminated soil and treating it in a bioreactor": This is an ex-situ method. The soil is removed.
(c) "Injecting microorganisms directly into the contaminated site": This describes an in-situ approach. The treatment occurs at the location of contamination. This can involve bioaugmentation (adding microbes) or biostimulation (adding nutrients/oxygen to enhance indigenous microbes).
(d) "Spraying chemical agents onto polluted surfaces": This describes chemical remediation, not bioremediation (which uses biological agents).
Therefore, injecting microorganisms directly into the contaminated site is an example of in-situ bioremediation. \[ \boxed{\text{Injecting microorganisms directly into the contaminated site}} \]