강의자료 ppt-10
인간의 삶과 역사 속의 미생물
2011-1학기
미생물은
어떤 존재인가?
환경 지킴이로서의 미생물
미생물과 오수 처리
Wastewater and sewage treatment
• 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 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 slimeforming 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
Hone septic tank system
• Frequently fail to work properly, contributing
to groundwater contamination
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