Bioremediation of hydrocarbon contaminated soils Flashcards
Why use biological treatments as opposed to others for removing contaminants in soil?
Cheaper
What is bioremediation?
The removal of contaminants using microorganisms
What is mineralisation?
A type of bioremediation; the decomposition or oxidation of chemical compounds in organic matter into plant accessible forms, opposite of immobilisation. Contaminants are used as food sources and destroyed
What is cometabolism?
Where contaminants are not used as food sources but are transformed into less hazardous chemicals
What is immobilisation?
Removal of metals by adsorption, precipitation, or accumulation
Outline the aerobic bioremediation process
Soil + contaminant –(O2, nutrients N, P, K)–> Microbe –> Soil + CO2 + water
What are some examples of biodegradables?
Crude oil and refined petroleum products, solvents, phenols, glycols, surfactants, some pesticides, explosives
What is ex situ bioremediation?
Where excavated soil is placed in a lined above-ground treatment area and aerated
What are three examples of ex situ bioremediation approaches?
Land farming, windrows, biopiles
What is the technology behind land farming?
Contaminated soil is spread on land Nutrient applied Moisture is added by irrigation/spraying Aeration through tilling Contaminants are degraded, transformed and immobilised by microbiological process and oxidation
What is the technology behind windrows?
Contaminated soil is placed in windrows
Nutrient amendment and/or bulking agents
Moisture added through irrigation/spraying
Aeration by windrow (compost) turner
What is the technology behind biopiles?
Contaminated soil placed in biopile
Nutrient/bulking agents added using Allu bucket (or similar)
Aeration achieved using Allu bucket
What are the advantages and disadvantages of using land farming as a bioremediation technique?
Adv: effective aeration; low equipment costs (tractor and tiller); low amendment costs (sprayer)
Dis: space; uncontrolled conditions (temp, rainfall); leaching - contamination of groundwater - requirement for liner (again, cost of space); dust control
What are the advantages and disadvantages of using windrows as a bioremediation technique?
Adv: compost fleece controls generation of leachate and dust; compost fleece helps maintain stable temp; reduced space over land farming
Dis: specialised equipment to turn windrows and handle fleece covers
What are the advantages and disadvantages of using biopiles as a bioremediation technique?
Adv: least space required; controlled leachate generation (cover and liner)
Dis: specialised equipment; irrigation and nutrient amendment most easily applied during construction
What is biostimulation?
Involves the modification of the environment to stimulate existing bacteria capable of bioremediation
How can biostimulation be achieved?
Through the addition of various forms of rate-limiting nutrients and electron acceptors e.g. phosphorous, nitrogen, oxygen, or carbon (e.g. in the form of molasses)
What are some examples of organic nutrients used for biostimulation?
Spent mushroom compost, manure, poultry litter, compost, sewage sludge
What is an example of inorganic nutrient used for biostimulation?
Fertiliser
What bulking agents can be used for biostimulation?
Wood chips, ground rice hulls
What is bioaugmentation?
The practice of adding cultured microorganisms into the subsurface for the purpose of degrading specific soil and groundwater contaminants
Can increase the % degradation in both light and heavy fractions of soils
What factors can affect bioremediation?
Pollutant characteristics = bioavailability, concentration, microbial toxicity
Microbial ecology = predators, interspecies competition
Physico-chemical characteristics = water content/humidity, organic matter content (soils), clay content (soils), pH
Microbiology = presence of co-substrates, genetics of relevant organisms, enzyme stability
Methodology = inoculation concentration, method of inoculation, presence/absence of indigenous activity, inoculum heterogeneity
What are two types of biodegradation?
Mineralisation: the conversion of an organic substance to its inorganic constituents, rendering the original compound harmless
Cometabolism: the transformation of a chemical by an organism while the organism uses a different substance as its primary energy or carbon source
