Bioremediation Flashcards
Bioremediation: definition, method, why
Use of biotechnology to remove or reduce pollution (in water, soil, food, ecosystems, etc) to acceptable levels
Microbes have evolved to use pollutants as energy/nutrition sources so we can utilise to reduce pollution via converting to something else
Why:
Industrial activities had low levels of regulation of dangerous compounds and accidents (chemical spills, etc)
Increased demand for development of new properties so now Brownfield sites (previously used for industry) want to be used for building houses on, but doesn’t meet regulation
Additionally, digging through soils from unsaturated zone (gaps in soil are air) to saturated zone (gaps in soil are water) then the soluble pollutants will move in water underground to sea, or a public well of water supply, or into field growing crops
Soil and water samples are tested to identify level of pollution
Pollution: definition, classes, examples, persistence,
Pollution is the introduction by man into the environment of substances liable to cause hazards to human health, harm to living resources and ecological damage
Pollution can be point source (factory smoke) requiring in-situ bioremediation or a non-point source (fumes from cars) requiring ex-situ bioremediation
Natural: compounds that occur naturally somewhere in the environment but human activity (mining industrial sites, metal smelting) leads to unnaturally high concentrations.
Ex. crude oil, heavy metals (lead, mercury, etc), carbon dioxide, phosphates
Xenobiotics: chemically synthesised compounds that have never occurred in nature
Ex. pesticides, herbicides, plastics
Persistance:
Pollutants can be classified as:
Degradable: Not stable in the environment
Degraded by biological and non-biological processes
Ex. simple hydrocarbons and petroleum fuels (degradability decrease as MW and degree of branching increase)
Persistent: Stable in the environment (at least in some conditions) for long
periods of time.
Recalcitrant: Intrinsically resistant to any degradation
When may using microbes be inefficient/difficult in bioremediation
Xenobiotics are likely to be more persistent/recalcitrant
because microbes have not had time to evolve pathways to degrade them. e.g. halogenated hydrocarbons
Insoluble compounds such as nylon, polyethylene and
other plastics are recalcitrant because of low biological availability (not in a form that can be taken up by microbe, too large). Microbes can’t access them to degrade them since insoluble in water
Heavy metals can’t be enzymatically degraded by microbes so instead are made less harmful via oxidation, precipitated (therefore less bioavailable), purified and reused, or concentrated and stored safely
Case study of bioremediation project
London Olympics 2012
* Clean-up of a 350-hectare area of East London for London 2012 Olympic Park.
* Started with >3,500 sampling locations, creating more
than 5 million chemical test results.
* 2.2 million square metres of soil was excavated, of which
764,000 square metres was treated by soil washing,
chemical stabilisation, bioremediation or sorting.
* 2,500 litres of free product (hydrocarbon) was removed and 235,000 square metres of contaminated groundwater pumped and treated.
Free products being the pollutant in it’s original form (not diluted in water, etc)
DDT: what it is, use, downside
DDT is a very effective insecticide (Paul Muller won the Nobel Prize in 1948 for developing)
Sprayed over crops, in houses, etc
Benefits
Controlled spread of malaria which provided crop protection
Downside
DDT is stable and slow to degrade.
Half-life in soil up to 30 years
Gets into insect, which a bird eats, which larger prey eats, etc (bioaccumulation occurs so concentration of pollutant increases going up the food chain)
Accumulates and persists in fatty tissue
DDT accumulated in bird eggs and breeding success declined
DDT ban increased breeding success
Mercury case study: how it occurred, effect, solution
Chisso factory producing acetaldehyde using a
Mercury Sulphate catalyst
* 1951 changed catalytic cycle leading to bi-product
methyl mercury
* 1956 first patient identified with central nervous system disease
* Local cats going crazy: “dancing cat” disease
* Families in coastal villages eating local fish and shellfish
* 1958/1959 cause identified as organic mercury
compounds. Bacteria convert inorganic mercury to
methyl mercury.
* Up to 2kg mercury per ton sediment at mouth of
plant outflow
* Company change waste-water route to pollute
river instead of harbour and installed “water treatment plant” that did not work
* Continued to pollute until 1968 when production
of acetaldehyde with mercury stopped
* Over 2000 certified victims and 10,000 other
claimants have been paid $100s millions in
compensation
Instead oxidised metal into form that can be collected or released in air. However, danger of microbes turning it into more toxic compounds
