강의자료 ppt-11 인간의 삶과 역사 속의 미생물 2012-1학기

미생물은 어떤 존재인가?

환경 지킴이로서의 미생물

미생물과 오수 처리

Wastewater and sewage treatment 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 treatment processes

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

Primary treatment of wastewater

Wastewater and sewage treatment 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)

Sludge digester for anoxic secondary wastewater treatment

Wastewater and sewage 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

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

Wastewater and sewage treatment 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

modern conventional sewage treatment plant

Hone septic tank system Frequently fail to work properly, contributing to groundwater contamination This system combines an anaerobic waste liquefaction unit (the septic tank) with an aerobic leach field. Biological oxidation of the liquefied waste takes place in the leach field, unless the soil becomes flooded.

미생물과 생물학적 환경정화 (bioremediation) * 생물학적 환경복원

Microbial bioremediation 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 and heavy metal transformations 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 (Hgo) which is volatile and nontoxic and oxidized to mercuric ion (Hg2+) photochemically Most mercury enters aquatic environments as Hg2+ which is more toxic than Hgo

Microbial bioremediation: Mercury and heavy metal transformations Hg2+ readily absorbs to particulate matter where it can be metabolized by microbes Some microbes form methylmercury (CH3Hg+), an extremely soluble and toxic compound (100 times more toxic than Hg2+) Several bacteria can also transform toxic mercury to nontoxic forms - Transform CH3Hg+ to Hg2+ and Hg2+ to Hg0

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

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

Environmental consequences of large oil spills 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

Taean oil spills

Taean oil spills

Taean oil spills

Taean oil spills

Microbial bioremediation: Petroleum biodegradation 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

Hydrocarbon-oxidizing bacteria in association with oil

Microbial bioremediation: Petroleum biodegradation 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: Biodegradation of xenobiotics 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

Examples of xenobiotic compounds

Persistence of herbicides and insecticides in soils

Persistence of herbicides and insecticides in soils

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

Chemistry of synthetic polymers