microbiology of the built environment

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Microbiology of the Built Environment

22


I. Mineral Recovery and Acid Mine Drainage

• 22.1 Mining with Microorganisms

• 22.2 Acid Mine Drainage


22.1 Mining with Microorganisms

• Pyrite (FeS2)

• one of the most common forms of iron in nature

• found in coals and in metal ores

• Sulfides also form insoluble minerals with metals.

• Economically feasible to mine low-grade ores only

if the metal can be concentrated



• Microbial leaching

• the removal of valuable metals, such as copper, from

sulfide ores by microbial activities (Figure 22.1)

• particularly useful for copper ores



• In microbial leaching, low-grade ore is dumped in a large pile (the leach dump) and sulfuric acid is added.

• The liquid emerging from the bottom of the pile is enriched in dissolved metals and transported to a precipitation plant. (Figure 22.2)

• Bacterial oxidation of Fe2+ is critical in microbial leaching, as Fe3+ itself can oxidize metals in the ores.



• Microorganisms are also used in the leaching ofuranium and gold ores. (Figure 22.3)

• Uranium leaching depends on the oxidation of U4+

to U6+ by Fe3+ with A. ferrooxidans reoxidizing Fe2+

to Fe3+.• Gold is deposited with minerals containing arsenic

and FeS2.• A. ferrooxidans and related bacteria can leach the

arsenic and pyrite.• Gold is then complexed with cyanide.

UO2+Fe2(SO4)3-> UO2SO4+2FeSO4

2FeAsS[Au]+7O2+2H2O+H2SO4->Fe2(SO4)3

+2H3AsO4+[Au]


22.2 Acid Mine Drainage

• Microbial leaching is also responsible for

environmental damage.

• Improperly handled coal or minerals are rich in sulfides.

• Oxidation of metal sulfides by bacteria can result in acidic

conditions. (Figure 22.4)


FeS2+14Fe3++8H2O->15Fe2++2SO42-+16H+


22.2 Acid Mine Drainage

• Acid mine drainage

• an environmental problem in coal-mining regions

• occurs when acidic mine waters are mixed with natural

waters in rivers and lakes (Figure 22.5)


II. Bioremediation

• 22.3 Bioremediation of Uranium-Contaminated

Environments

• 22.4 Bioremediation of Organic Pollutants:

Hydrocarbons

• 22.5 Bioremediation of Organic Pollutants:

Pesticides and Plastics


22.3 Bioremediation of Uranium-Contaminated Environments• Uranium contamination of groundwater has

occurred where uranium has been processed or

stored. (Figure 21.6)

• Some bacteria can convert U6+ to U4+.

• U6+ is water soluble.

• U4+ is NOT water soluble.

• Uranium is contained, not removed.


22.4 Bioremediation of Organic Pollutants: Hydrocarbons• Organic pollutants can eventually be completely

degraded to CO2 by microbes.

• Prokaryotes have been used in bioremediation of

several major crude oil spills. (Figure 22.7)


22.4 Bioremediation of Organic Pollutants: Hydrocarbons• Diverse bacteria, fungi, and some cyanobacteria

and green algae can oxidize petroleum products aerobically.

• Oil-oxidizing activity is best if temperature and inorganic nutrient concentrations are optimal, so these nutrients are often added.

• Hydrocarbon-degrading bacteria attach to oil droplets, decompose the oil, and disperse the slick. (Figure 22.8)


Alcanivorax borkumensis


22.4 Bioremediation of Organic Pollutants: Hydrocarbons• Gasoline and crude oil storage tanks are potential

habitats for hydrocarbon-oxidizing microbes.

(Figure 22.9)

• If sufficient sulfate is present in the oil, sulfate-

reducing bacteria can grow and consume

hydrocarbons while in the tank.


22.4 Bioremediation of Organic Pollutants: Pesticides and Plastics• Xenobiotic compound

• synthetic chemicals that are not naturally occurring

• examples: pesticides, polychlorinated biphenyls,

munitions, dyes, and chlorinated solvents

(Figure 22.10)

• Many degrade extremely slowly because organisms

lack enzymes to recognize these new compounds.


22.4 Bioremediation of Organic Pollutants: Pesticides and Plastics• Pesticides

• common components of toxic wastes

• include herbicides, insecticides, and fungicides

• represent a wide variety of chemicals

• Some can be used as carbon sources by microorganisms.

• Some can be used as electron donors.


22.4 Bioremediation of Organic Pollutants: Pesticides and Plastics• Some xenobiotics can be degraded partially or

completely if another organic material is present

as a primary energy source for a microbe. The

microbe breaks down the xenobiotic and the

organic molecule (cometabolism).


22.4 Bioremediation of Organic Pollutants: Pesticides and Plastics• Chlorinated xenobiotics can be degraded.

(Figure 22.11)

• anaerobically (reductive dechlorination)

• aerobically (aerobic dechlorination)

• Reductive dechlorination is usually a more

important process because anoxic conditions

develop quickly in polluted environments.


22.4 Bioremediation of Organic Pollutants: Pesticides and Plastics• Plastics of various types are xenobiotics that are

not readily degraded by microorganisms.

(Figure 22.12)

• The recalcitrance of plastics has fueled research

efforts into a biodegradable alternative

(biopolymers or microbial plastics).


Ralstonia eutropha


III. Wastewater and Drinking Water Treatment

• 22.6 Primary and Secondary Wastewater

Treatment

• 22.7 Advanced Wastewater Treatment

• 22.8 Drinking Water Purification and Stabilization

• 22.9 Municipal and Premise Water Distribution

Systems


III. Wastewater and Drinking Water Treatment

• Water

• potential common source of infectious diseases (e.g.

Cholera)

• can also be a source for chemically induced intoxications

• Ensuring water purity is essential for public health.

• Treatment and purification schemes use microorganisms

to identify, remove, and degrade pollutants.


22.6 Primary and Secondary Wastewater Treatment• Wastewater

• domestic sewage or liquid industrial waste• “Gray water” is the water resulting from washing, bathing,

and cooking.• Sewage is water contaminated with human and animal

fecal material.• Wastewater treatment

• relies on industrial-scale use of microbes for bioconversion

• Following treatment, the discharged treated wastewater (effluent water) is suitable for

• release into surface waters• release to drinking water purification facilities


22.6 Primary and Secondary Wastewater Treatment• Wastewater treatment facility

• goals: to reduce organic and inorganic materials in

wastewater to a level that no longer supports microbial

growth and to eliminate other potentially toxic materials

• The efficiency of treatment is expressed in terms of a

reduction in the biochemical oxygen demand (BOD).• amount of dissolved oxygen consumed by microbes to

completely oxidize all organic and inorganic matter in a

water sample


22.6 Primary and Secondary Wastewater Treatment• Wastewater treatment is a multistep operation

employing both physical and biological processes.

(Figure 22.13)• Primary, secondary, and sometimes advanced

treatments are used.

• primary treatment

• uses physical separation methods to separate solid and

particulate organic and inorganic materials from

wastewater (Figure 22.14)


22.6 Primary and Secondary Wastewater Treatment• Secondary treatment

• Aerobic secondary treatment uses digestive reactions

carried out by microbes under aerobic conditions to treat

wastewater with low levels of organic materials

• Activated sludge (Figure 22.15a and b) and the trickling

filter (Figure 21.15c) are the most common decomposition

processes.


22.6 Primary and Secondary Wastewater Treatment• Secondary treatment

• Anaerobic secondary treatment involves a series of

digestive and fermentative reactions carried out by

various microbes under anoxic conditions. (Figure 22.17)

• The process is carried out in large enclosed tanks

(sludge digesters or bioreactors).


22.6 Primary and Secondary Wastewater Treatment• In the activated sludge process, wastewater is

mixed and aerated in large tanks (Figure 22.15a

and b), and slime-forming bacteria (e.g., Zoogloea

ramigera; Figure 22.16) grow and form flocs.

• Most treatment plants chlorinate the effluent after

secondary treatment to further reduce the possibility

of biological contamination.


22.7 Advanced Wastewater Treatment

• Tertiary treatment

• any physiochemical or biological treatment process added for the further processing of secondary treatment effluent

• additional removal of organic matter and suspended solids

• reduces the levels of inorganic nutrients (e.g., phosphate, nitrate, nitrite)

• most complete method of treating sewage but, because of costs, is not widely adopted



• Example of tertiary treatment

• phosphorus removal

• chemical precipitation

• enhanced biological phosphorous removal (EBPR;

Figure 22.18)

• uses phosphorus-accumulating organisms

• sequential passage through anaerobic and aerobic

bioreactors



• Contaminants of emerging concern• Wastewater treatment is designed for human waste

and/or industrial waste.• New biologically active pollutants are being released in

treated or untreated sewage.• pharmaceuticals

• personal care products

• household products

• sunscreens

• New treatment systems will have to degrade these chemicals.


22.8 Drinking Water Purification and Stabilization• Wastewater treated by secondary methods is not

yet potable, or safe for human consumption.

• Further treatment is required to remove pathogens,

eliminate taste and odor, reduce chemicals (e.g.,

iron, manganese), and decrease turbidity.

• A typical drinking water treatment installation

purifies raw (untreated) water. (Figure 22.20)


22.8 Drinking Water Purification and Stabilization• Purification involves many steps. (Figure 22.20)

• sedimentation to remove particles

• Coagulation and flocculation form additional aggregates,

which settle out.

• filtration

• disinfection (typically with chlorine gas or UV radiation)


22.9 Water Distribution Systems

• Water must travel through miles of pipe to reach consumer/ (Figure 22.21)

• municipal pipes

• domestic pipes

• Problems of water distribution

• taste and odor problems

• protect or promote growth of pathogens

• select for more pathogenic bacteria

• select for resistant bacteria



• Elimination of microbial growth in distribution systems requires• complete nutrient removal• maintaining appropriate residual chlorine levels

• Neither is possible.• Opportunistic pathogens are found in water

distribution systems.• Grazing protists are also found in water distribution

systems. (22.22)



• Some opportunistic pathogens survive and grow

within protists. (Figure 22.21)

• Legionella pneumophila

• Pseudomonas sp.

• Mycobacterium sp.

• Opportunistic pathogens are enriched in showerheads.


IV. Indoor Microbiology and MicrobiallyInfluenced Corrosion• 22.10 The Microbiology of Homes and

Public Spaces

• 22.11 Microbially Influenced Corrosion of Metals

• 22.12 Biodeterioration of Stone and Concrete


22.10 The Microbiology of Homes and Public Spaces• Humans in an urban environment spend the

majority of time indoors, sharing their world with

microbes.

• Microbiota inhabit the air, dust, surfaces, and ventilation

and water systems. (Figure 22.23)

• This may increase exposure to pathogens but may also

decrease overall exposure, which may lead to allergies.


22.10 The Microbiology of Homes and Public Spaces• The microbiota of a home is very predictive of

specific family, and the microbiota changes within days of a change of occupancy.

• Flushing a toilet can release 100,000 small bacteria into the air, which can then transmit enteric bacteria from person to person.

• Sexually transmitted diseases, however, are unlikely to be transmitted in this way because they are sensitive to drying out and would die before transmission.


22.11 Microbially Influenced Corrosion of Metals

• Corrosion is a complex process

• Microorganisms accelerate corrosion by

• changing pH

• changing redox

• production of corrosive metabolites

• production of corrosive microenvironments (biofilms)



• Microbially influenced corrosion (MIC) is corrosion

in which microbes are implicated.

• sulfate-reducing bacteria

• ferric-iron-reducing bacteria

• ferrous-iron-oxidizing bacteria

• methanogens



• Metal corrosion by sulfate-reducing bacteria

(Figure 22.24)

• Seawater contains sulfate.

• Sulfate is a metabolic reactant.

• H2S is a metabolic product.

• H2S is corrosive.


22.12 Biodeterioration of Stone and Concrete

• Biodeterioration is the loss of structural integrity of stone or concrete caused by microorganisms.

• Microorganisms can colonize the surface of stone. • Microorganisms can grow within certain stones

(endolithic).• Bacteria

• Archaea

• fungi• algae• cyanobacteria


22.12 Biodeterioration of Stone and Concrete

• Rapid form of biodeterioration occurs in crown

corrosion of concrete sewer lines (Figure 22.25)

• result of sulfate-reducing bacteria and sulfide-oxidizing

bacteria

• Biodeterioration also occurs in concrete holding

tanks and cooling towers.

microbiology of the built environment

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