인간의 삶과 역사 속의 미생물 학기 강의자료 ppt-10

미생물은 어떤 존재인가 ?

환경 지킴이로서의 미생물

미생물과 오수 처리

Wastewater –Domestic sewage or liquid industrial waste 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 –Wastewater treatment processes Similar to self-purification processes observed in rivers and streams except are controlled and intensified Wastewater and sewage treatment

Wastewater treatment facility –Its goal is 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 (= biological oxygen demand, BOD) The relative amount of dissolved oxygen consumed by microbes to completely oxidize all organic and inorganic matter in a water sample Wastewater and sewage treatment

Wastewater treatment is a multistep operation employing both physical and biological processes –Primary, secondary, and sometimes tertiary treatments are used Wastewater and sewage treatment

Wastewater treatment processes

Primary treatment –Uses physical separation methods to separate solid and particulate organic and inorganic materials from wastewater Wastewater and sewage treatment

Primary treatment of wastewater

Secondary Treatment –Anoxic secondary treatment involves a series of digestive and fermentative reactions carried out by various microbes under anoxic conditions The process is carried out in large enclosed tanks (sludge digesters or bioreactors) Wastewater and sewage treatment

Sludge digester for anoxic secondary wastewater treatment

Secondary treatment (cont’d) –Aerobic secondary treatment uses digestive reactions carried out by microbes under aerobic conditions to treat wastewater with low levels of organic materials The trickling filter ( 살수여상법 [ 撒水濾床法 ]) and activated sludge ( 활성오니법 [ 活性汚泥 ]) are the most common decomposition processes Wastewater and sewage treatment

Aerobic secondary wastewater treatment processes Trickling filter in a treatment facility

Aerobic secondary wastewater treatment processes Aeration tank of an activated sludge installation

Aerobic secondary wastewater treatment processes Wastewater flow through an activated sludge installation

In the activated sludge process, wastewater is mixed and aerated in large tanks and slime- forming bacteria (e.g., Zoogloea ramigera) grow and form flocks Most treatment plants chlorinate the effluent after secondary treatment to further reduce the possibility of biological contamination Wastewater and sewage treatment

Tertiary Treatment –Any physiochemical or biological process employing precipitation, filtration, or chlorination procedures similar to those used for purification of drinking water –Reduces the levels of inorganic nutrients (e.g., phosphate, nitrate, nitrite) –Most complete method of treating sewage but it has not been widely adopted due to costs Wastewater and sewage treatment

Frequently fail to work properly, contributing to groundwater contamination Hone septic tank system

미생물과 생물학적 환경정화 (bioremediation) * 생물학적 환경복원

Mercury and heavy metal transformations Petroleum biodegradation ( 생물학적분해 ) Biodegradation of xenobiotics * Xenobiotics: A completely synthetic chemical compound not naturally occurring on Earth Microbial bioremediation

Mercury is of environmental importance because of its tendency to concentrate in living tissues and its high toxicity The major form of mercury in the atmosphere is elemental mercury (Hg o ) which is volatile and nontoxic and oxidized to mercuric ion (Hg 2+ ) photochemically Most mercury enters aquatic environments as Hg 2+ which is more toxic than Hg o Microbial bioremediation: Mercury and heavy metal transformations

Hg 2+ readily absorbs to particulate matter where it can be metabolized by microbes Some microbes form methylmercury (CH 3 Hg + ), an extremely soluble and toxic compound (100 times more toxic than Hg 2+ ) Several bacteria can also transform toxic mercury to nontoxic forms - Transform CH 3 Hg + to Hg 2+ and Hg 2+ to Hg 0 Microbial bioremediation: Mercury and heavy metal transformations

Prokaryotes have been used in bioremediation of several major crude oil spills Microbial bioremediation: Petroleum biodegradation

Environmental consequences of large oil spills Contaminated Beach in Alaska containing oil from the Exxon Valdez spill of 1989

Oil spilled into the Mediterranean Sea from a power plant Environmental consequences of large oil spills

Center rectangular plot (arrow) was treated with inorganic nutrients to stimulate bioremediation Environmental consequences of large oil spills

Taean oil spills

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 Hydrocarbon-degrading bacteria attach to oil droplets and decompose the oil and dispense the slick Microbial bioremediation: Petroleum biodegradation

Hydrocarbon-oxidizing bacteria in association with oil

Gasoline and crude oil storage tanks are potential habitats for hydrocarbon-oxidizing microbes - If sufficient sulfate is present, sulfate-reducing bacteria can grow and consume hydrocarbons Microbial bioremediation: Petroleum biodegradation

Xenobiotic compound –Synthetic chemicals that are not naturally occurring e.g., pesticides, polychlorinated biphenyls, munitions, dyes, and chlorinated solvents –Many degrade extremely slowly Microbial bioremediation: Biodegradation of xenobiotics

Pesticides –Common components of toxic wastes –Include herbicides, insecticides, and fungicides –Represent a wide variety of chemistries Some of which can be used as carbon sources and electron donors by microbes Microbial bioremediation: Biodegradation of xenobiotics

Examples of xenobiotic compounds

Persistence of herbicides and insecticides in soils

Plastics of various types are xenobiotics that are not readily degraded by microbes Microbial bioremediation: Biodegradation of xenobiotics

Chemistry of synthetic polymers