Chapter 4 Risk Management of Land Contamination PP

Question 1

Define what is meant by bioremediation and state two pollutants that can be treated using this technology.

Answer 1

Bioremediation – the use of microorganisms in the treatment of environmental pollution / waste.

• Oil spills
• Chlorinated pesticides

Question 2

Describe the process of bioremediation.

Answer 2

adding microorganisms to soils to remove contaminants

Question 3

Complete the table to identify the possible pollutants that they can be used to treat

psuedomonas putida
pseudomonas aeruginosa
dehalococcoides ethenogenes

Answer 3

organic solvents
oil contamination
halogenated hydrocarbons

Question 4

Discuss the economic and environmental benefits of using bioremediation technology compared to traditional treatment methods.

Answer 4

Bioremediation can be carried out under atmospheric conditions. Bioremediation can be carried out in situ so soil is not removed from the site. The contaminants are reduced to (almost) zero. The by-products are non-toxic so water and air pollution is minimised. Bioremediation uses bacteria that occur naturally in the soil so the ecosystem is maintained. Bioremediation is economical because it does not require large energy inputs.

Traditional treatment;
Traditional treatment is expensive because of the high energy costs (heating). Greenhouse gases such as carbon dioxide are produced. Soil may need to be treated ex situ / off site which required heavy machinery. Traditional treatment can produce toxic by-products which require further treatment. Soil may need to be disposed of after treatment which leads to increased landfill.

Question 5

Outline the role of genetic engineering in modifying micro-organisms for bioremediation.

Answer 5

Micro-organisms can be genetically engineered to decontaminate a site more rapidly than unmodified micro-organisms and Remove toxic materials such as heavy metals.

Question 6

Identify two issues of concern from the use of genetic engineering of micro-organisms for bioremediation.

Answer 6

Genetically engineered micro-organisms may wipe out existing bacteria. They may affect the existing soil ecology with unknown consequences

Question 7

Evaluate the use of Alpine Pennygrass in the decontamination of a suitable brown field site.

Answer 7

advantages
The cost of phytoremediation is lower than that of traditional processes both on and off site.This can prove to be cost effective as the initial cost of Alpine Pennygrass is low whilst the potential for recovery of sale of contaminant metals is high. The plants can accumulate and tolerate high levels of toxic metal ions.

Limitations;

• Phytoremediation is limited to the surface area and depth occupied by the roots.
• The use of Alpine Pennygrass has low environmental impact although plants cannot absorb all contaminants and will eventually be killed by toxicity of the soil.
• There is a potential threat to the food chain by contaminated Alpine Pennygrass.

Question 8

describe the process of Phytoextraction.

Answer 8

Plants ‘uptake’ metals from contaminated soils and concentrate them in above ground plant tissue / biomass. This is then harvested for disposal and / or metal recovery

Question 9

Name one plant species used for Phytoextraction and the metal ore that it can extract.

Answer 9

White mustard to extract copper

Question 10

Define Biohydrometallurgy

Answer 10

Biohydrometallurgy: The use of bacteria (micro-organisms) to extract valuable metals from low grade ore