Lecture 14.pdf

BIOL371: Microbiology Lecture 14 – Microbiology of the built environment 1 Topics of today 1. 2. 3. 4. Mineral recovery and acid mine drainage Bioremediation Wastewater and drinking water treatment Indoor microbiology and microbially influenced corrosion Materials covered:  Chapters 22.1-22.1...

BIOL371: Microbiology Lecture 14 – Microbiology of the built environment 1 Topics of today 1. 2. 3. 4. Mineral recovery and acid mine drainage Bioremediation Wastewater and drinking water treatment Indoor microbiology and microbially influenced corrosion Materials covered:  Chapters 22.1-22.13  Figures 22.2, 22.3-22.6, 22.8, 22.11, 22.14, 22.15, 22.17, 22.22, 22.23, 22.26, 22.28 2 Mineral recovery and acid mine drainage 1. Mining and microorganisms 2. Acid mine drainage 3 Microbial leaching of copper  In microbial leaching, low-grade ore is dumped in a large pile  Dilute sulfuric acid (pH 2) is added  The liquid emerging from the bottom of the pile is enriched in dissolved metals and transported to a precipitation pond  Bacterial oxidation of ferrous ion (Fe2+) to ferric ion (Fe3+) in the oxidation pond is critical as Fe3+ is used to oxidize other metals in the ores  About a quarter of all copper mined worldwide is obtained by microbial bleaching 4 Microbial leaching of uranium and gold  Uranium leaching depends on the oxidation of U4+ to U6+ by Fe3+ with Acidithiobacillus ferrooxidans reoxidizing Fe2+ to Fe3+; U6+ in the form of uranyl sylfate (UO2SO4) is highly soluble and can be concentrated  Gold leaching: gold is deposited with minerals containing arsenic and FeS2  Acidithiobacillus ferrooxidans and related bacteria leach the arsenic and pyrite  Gold is then complexed with cyanide Gold leaching tanks: a mixture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans solubilizes the pyrite/arsenic mineral containing trapped gold, which releases the gold. 5 Acid mine drainage  Microbial leaching is responsible for environmental damage  Coal or minerals are rich in sulfides  Oxidation of metal sulfide by bacteria can result in acidic conditions  Acid mine drainage: an environmental problem in coal-mining regions  Occurs when acidic mine waters are mixed with natural waters in rivers and lakes pH can drop <1  Degrades water quality because both the acid and the dissolved metals (iron, aluminum, and heavy metals such as cadmium and lead) are toxic to aquatic organisms The yellowish-red colour is due to the 6 precipitated iron oxides in the drainage Bioremediation 1. Bioremediation of uranium-contaminated environments 2. Bioremediation of organic pollutants: hydrocarbons 3. Bioremediation of microbial degradation of major chemical; pollutants: chlorinated organics and plastics 7 Bioremediation of uranium-contaminated environments  Where uranium has been processed or stored, groundwater can be contaminated with uranium  Some bacteria can convert U6+ to U4+  U6+ is water soluble  U4+ is not water soluble  Uranium is contained, not removed Organic carbon (acetate) is being infused into the site. Acetate is an electron donor for reduction of U6+ to U4+, which immobilizes the uranium. 8 Bioremediation of organic pollutants: hydrocarbon  With time, organic pollutants can be completely degraded to CO2 by microbes  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  Gasoline and crude oil storage tanks are potential habitats for hydrocarbonoxidizing microbes  If sufficient sulfate is present in the oil, sulfate-reducing bacteria can grow and consume hydrocarbons while in the tank Hydrocarbon-degrading bacteria attach to oil droplets, decompose the oil, and disperse the slick 9 Bioremediation of chlorinated organics  Xenobiotic compounds: synthetic chemicals that are not naturally occurring  Examples: pesticides, polychlorinated biphenyls (PCBs), munitions, dyes  Degrade extremely slowly because organisms lack enzymes to recognize these compounds  microorganisms that degrade chlorinated compounds are widespread in nature and evolved a natural halogen cycle long before the introduction of manufactured chemicals OH Pentachlorophenol catabolism by Sphingabium chlorophenolicum: involving both hydroxylating monooxygenase and ring-cleavage dioxygenase 10 Biodegradation of plastics  Plastics are NOT readily degraded by microorganisms  Polyethylene terephthalate (PET) used to make drinking bottles is the only petroleum-based plastic that can be extensively degraded by microorganism 11 Wastewater and drinking water treatment 1. 2. 3. 4. 5. Primary and secondary wastewater treatment Tertiary wastewater treatment Contaminants of emerging concern Drinking water purification and stabilization Water distribution systems 12 Goals of wastewater treatment  Wastewater: domestic sewage or liquid industrial waste  Gray water: water resulting from washing, bathing, and cooking  Sewage: water contaminated with human and animal fecal material  Wastewater treatment: industrial-scale use of microorganisms for bioconversion  Main goals: to reduce organic and inorganic materials to a level that no longer supports microbial growth and to eliminate potentially toxic materials  The efficiency of treatment is expressed in terms of a reduction in the biochemical oxygen demand (BOD)  The amount of dissolved oxygen consumed by microbes to completely oxidize all organic and inorganic matter in a water sample 13 Multistep operation of wastewater treatment  Wastewater treatment is a multistep operation employing both physical and biological processes  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 14 Aerobic 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: microorganisms in the aeration tank are responsible for oxidative degradation of the organic components of the wastewater  Trickling filter: wastewater is distributed slowly by a rotating arm onto a bed of rocks (10-15 cm diameter) Aeration tank of an activated sludge installation (30 meter long, 10 meter wide, and 5 meter deep) Wastewater flow through an activated sludge installation Trickling filter: the rotating arms distribute wastewater slowly and evenly on the rock bed (2 meter deep) 15 Anaerobic secondary treatment – anaerobic digester  In the activated sludge process, wastewater is mixed and aerated in large tanks, and slime-forming bacteria (e.g., Zoogloea ramigera) grow and form flocs  A series of digestive and fermentative reactions carried out by various microbes under anoxic conditions in large enclosed tanks (sludge digesters or bioreactors)  Most treatment plants chlorinate the effluent after secondary treatment to reduce biological contamination 16 Tertiary wastewater treatment  Tertiary treatment: any physicochemical or biological treatment processes for further processing of secondary treatment effluent  Most complete method of treating sewage  Additional removal of organic matter and suspended solids  Reduces the levels of inorganic nutrients (e.g., phosphate, nitrate, nitrite)  Example: uses phosphorus-accumulating organisms to remove phosphorus  Not widely adopted owing to cost 17 Emerging concerns  Wastewater treatment to date is designed for human and/or industrialwastes  New biologically active pollutants are being released in treated or untreated sewage  Pharmaceuticals  Personal care products  Household products  Sunscreens  New treatment systems are required to remove or degrade these chemicals 18 Drinking water purification system  Multiple steps involved in purification  Sedimentation to remove particles  Coagulation and flocculation to form additional aggregates for sedimentation  Filtration  Disinfection – typically chlorine gas or UV irradiation Aerial view of a drinking water treatment plant in Louisville, Kentucky, USA; Ohio River is the source water. Arrows show the direction of water flow. 19 Issues with water distribution systems  Water must travel through kilometers of municipal and domestic pipes to reach consumers  Problems with water distribution: taste and odor; microbial growth  Elimination of microbial growth in water distribution system requires  Complete nutrient removal  Maintaining appropriate level of chlorine  Neither of the above is feasible  Opportunistic pathogens are found in water distribution systems including showerheads  Some opportunistic pathogens grow within protists; e.g., Legionella pneumophilia, Mycobacterium 20 The microbiology of homes  Microorganisms inhabit the sir, dust, surfaces, and ventilation and water systems  The microbiota of a home is very predictive of specific family, and can change within days of a change of occupancy  Flushing a toilet can release 100,000 bacteria into the air 21 Microbially influenced corrosion of metals  Microorganisms can accelerate corrosion of metals by:  Changing pH  Changing redox  Production of corrosive metabolites  Production of corrosive microenvironments (biofilms)  Bacteria implicated in metals corrosion include: sulfate-reducing bacteria, ferriciron-reducing bacteria, ferrous-ironoxidizing bacteria, and methanogens Sulfate-reducing bacteria consume organic material in the anoxic wastewater, producing H2S. The latter is oxidized by sulfur-oxidizing chemolithotrophic bacteria that attach to the oxic upper (crown) pipe surface, accelerating corrosion from the production of H2SO4 (sulfuric acid). 22 Biodeterioration of stone and concrete  Biodeterioration: loss of structural integrity caused by microorganisms  Microorganisms can colonize the surface of stone 23