1. 강의자료 ppt-11
인간의 삶과 역사 속의 미생물
2012-1학기

2. 미생물은 어떤 존재인가?

3. 환경 지킴이로서의 미생물

4. 미생물과 오수 처리

5. 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

6. 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

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

8. Wastewater treatment processes

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

11. Primary treatment of wastewater

12. 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)

13. Sludge digester for anoxic secondary wastewater treatment

14. 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

15. Aerobic secondary wastewater treatment processes
Trickling filter in a treatment facility

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

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

18. 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

19. 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

20. modern conventional sewage treatment plant

21. 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.

22. 미생물과 생물학적 환경정화 (bioremediation)
* 생물학적 환경복원

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

24. 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

25. 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

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

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

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

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

30. Taean oil spills

31. Taean oil spills

32. Taean oil spills

33. Taean oil spills

34. 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

35. Hydrocarbon-oxidizing bacteria in association with oil

36. 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

37. 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

38. 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

39. Examples of xenobiotic compounds

40. Persistence of herbicides and insecticides in soils

41. Persistence of herbicides and insecticides in soils

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

43. Chemistry of synthetic polymers