Define what is meant by bioremediation and state two pollutants that can be
treated using this technology.
Bioremediation – the use of microorganisms in the treatment of environmental
pollution / waste. {1}
Any two pollutants from;
• Oil spills
• Chlorinated pesticides
• Heavy metals.
• Diesel oil
• PCBs.
{1} per correct pollutant, max of 2 marks
Describe the process of bioremediation. {2}
Adding micro-organisms to soils {1} to remove contaminants {1}
What name is given to the treatment of contaminated land with micro-
organisms? {1}
Bioremediation {1}
Name three contaminants which can be treated by micro-organisms through
the process of bioremediation. {3}
Any three from:
• waste oil,
• heavy metals,
• chlorinated pesticides,
• polychlorinated biphenyls (PCBs) and
• diesel oil
All relevant, valid responses should be given credit. (3 × [1])
Identify a pollutant that the following micro-organisms can be used to treat:
1: Pseudomonas aeruginosa {1}
2: Dehalococcoides ethenogenes {1}
Any one from:
1: Oil/ petrol/diesel/hydrocarbons/heavy metals/toxic metals/dyes/
cadmium/manganese/iron/chromium {1}
2: Halogenated hydrocarbons/chlorinated hydrocarbons/any named
example (e.g. chloroethene) {2}
Discuss the economic and environmental benefits of using bioremediation
technology compared to traditional treatment methods. {6}
• 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.
Describe two benefits associated with the use of the type of contaminated
land treatment named bioremediation
Any two benefits from:
• The clean-up of the site is done on the site itself without disturbing the
surrounding environment. [2]
• Less energy is required because the micro-organisms work at
atmospheric temperatures. [2]
• Clean-up times can be reduced significantly which saves on costs. [2]
• The process requires less labour so costs are reduced. [2]
Award [2] for a detailed explanation and [1] for a limited explanation.
Discuss one economic benefit and one environmental benefit of using
bioremediation technology compared with traditional treatment methods.
Economic benefit:
Bioremediation can be carried out in-situ cutting out transportation costs as
soil is transported to treatment facility. [1] Contaminants can be reduced to
near zero without having to excavate and pay for new soil to be brought in.
[1]
Environmental benefit:
There is no excavation or transportation required [1] which lowers carbon
emissions from machinery and limits damage to local ecosystems. [1]
Outline the role of genetic engineering in modifying micro-organisms for
bioremediation. Your answer should focus on two points. {2}
Any two points from below;
Micro-organisms can be genetically engineered to;
• Decontaminate a site more rapidly than unmodified micro-organisms.
• Tolerate harsher conditions.
• Remove toxic materials (such as heavy metals).
Identify two issues of concern from the use of genetic engineering of micro-
organisms for bioremediation. {2}
Any two points from;
• Genetically engineered micro-organisms may wipe out existing bacteria.
• They may affect the existing soil ecology with unknown consequences.
• They may not behave the same way in the field as they do under
laboratory conditions.
Name a method used to modify micro-organisms to enhance their
bioremediation properties. {1}
Genetic engineering
Explain how in situ bioreactors are used to treat contaminated soil. {3}
The bioreactor is placed below ground level. {1}
Contaminated ground water is circulated / pumped through the bioreactor. {1}
Micro-organisms in the bioreactor break down contaminants. {1}
Evaluate the use of Alpine Pennygrass in the decontamination of a suitable
brown field site. {6}
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.
describe the process of Phytoextraction. {3}
Phytoextraction; Plants ‘uptake’ metals from contaminated soils {1} and
concentrate them in above ground plant tissue / biomass {1}. This is then
harvested for disposal and / or metal recovery {1}.
Name one plant species used for Phytoextraction and the metal ore that it can
extract. {1}
Example: Choose one from;
• White mustard {1} to extract copper {1}
• Sunflowers {1} to extract gold {1}.
With reference to copper, discuss the similarities and differences between
phytoremediation and phytoextraction. You should discuss four points in your
answer. {6}
Similarities:
* Both involve plants
* Both involve uptake of the metal into the plant tissue through
the roots
Differences:
* Phytoremediation involves removal of copper/metal
contaminant. Phytoextraction involves extraction of copper for commercial use.
* The plant for phytoremediation must be disposed of carefully.
The metal-containing plant used for phytoextraction is harvested and ashed to
aid with metal extraction.
* The plant used for phytoremediation is likely to contain a
range of metals so the copper cannot easily be extracted from it. The plant for
phytoextraction is used on soil containing metal ore mine tailings so it contains
the target metal
* Alpine pennygrass and/ or Indian mustard can be used for
copper phytoremediation. White mustard can bs used for copper
phytoextraction.
What is the use of plant species to extract metals from metal ore mine tailings. {1}
Phytoextraction {1}
Name and describe the process which uses plant species to extract metal from
ore mine tailings. Your answer should include an example of a plant which can
carry out this process and the name of the metal which it can extract.
Name of process: Phytoextraction [1]
Description:
Phytoextraction makes use of a plant’s ability to hyperaccumulate a metal. [1]
The site should be tested to see what metals are present in the soil and then
the appropriate plant should be grown on the contaminated site. [1] When the
plant has grown it is harvested and burned in a controlled environment. [1] The
metal is then extracted from the ash. [1]
Discuss and evaluate phytoremediation as a possible method which could have
been used to decontaminate the land. {8}
Your answer should focus on the following areas:
• The process of phytoremediation.
• The advantages of phytoremediation compared to traditional
treatment methods.
• The limitations of phytoremediation compared to traditional
treatment methods.
The process of phytoremediation.
• In phytoremediation soil is tested and the contaminant is identified. Once
identified the correct plant is chosen and planted.
• Plants extract the metals from the soil through their root systems and
retain the metal in their tissues.
• Once inside the plant, heavy metal ions can be stored in the roots,
stems, or leaves. When the plants have grown and absorbed the metal
pollutants they are harvested and disposed of safely.
The advantages of phytoremediation compared to traditional treatment
methods.
• It is ecologically friendly, taking advantage of natural processes to use
nature to cleanse nature.
• It uses energy from the sun, therefore is less energy intensive than
traditional decontamination methods.
• It has a positive public perception.
• Easy to implement.
The limitations of phytoremediation compared to traditional treatment
methods.
• the depth of the treatment area is limited to the length of the plant’s roots.
• It may be seasonal.
• It takes a long time compared to traditional methods of decontamination.
• It can transfer contamination across media, e.g. from soil to air, but only
for the volatile pollutants.
• It is not effective for strongly absorbed (e.g. PCBs) and weakly absorbed
contaminants.
• Products may be mobilised into ground water or bio accumulated in
animals if the accumulating plants are not harvested after growth.
Describe, using four stages, the process of how metal ore is extracted by
plants. {4}
Phytoextraction: Metal to be extracted is identified by testing the soil and the
correct species of plant is planted. [1]
Plants ‘uptake’ metals from contaminated soils [1]
and concentrate them in above-ground plant tissue/biomass. [1]
This is then harvested for disposal and/or metal recovery. [1]
