1. Applied Environmental Microbiology
Chapter 42
Applied Environmental Microbiology

2. Water Purification and Sanitary Analysis
microbial containment candidates
potential pathogens that can survive in water and represent severe health risks
water purification
critical link in controlling waterborne disease

3. Table 42.1

4. Water Purification…
water held with high levels of suspended material  sedimentation basin
large particles settle out
partially clarified water mixed with chemicals such as alum and lime and  settling basin
more material precipitates out in coagulation or flocculation process
removes microbes, organic matter, toxic contaminants and suspended fine particles

5. Figure 42.1

6. Water Purification… water  rapid sand filters
physically traps fine particles and flocs
water treated with disinfectant
chlorine
concern about disinfection by-products (DBPs) such as trihalomethanes (THMs) which may be carcinogens
ozone

7. Water Purification…
EPA has developed regulations called the Long Term 2 Enhanced Surface Water Treatment Rule (LT2 rule)
sets maximum containment level goal (MCLG) for specific pathogens
health goals set at a level at which no known or anticipated adverse effects on health of persons occur and which allows an adequate margin on safety

8. Problem Microbes
not consistently removed by coagulation, rapid sand filtration, and disinfection processes
Giardia lamblia
“backpackers disease”
slow sand filters effectively remove Giardia cysts
Cryptosporidium
small protozoan with oocysts that escape usual purification schemes
Cyclosporan
protozoan that causes diarrhea
viruses
up to 99.9% are removed by usual purification schemes, but this not considered sufficient protection

9. Water Purification
precise treatment depends on level of contamination but generally involves filtration techniques
slow sand filters
water passed over bed of sand with microbial layer (biofilm) cover the surface of each sand grain
waterborne microbes are removed by adhesion to biofilm
aeration and disinfection also used

10. Sanitary Analysis of Waters
based on detecting indicator organisms
indicate fecal contamination of water supplies
indicate possible contamination by human pathogens

11. “Ideal” Indicator Organism
suitable for analysis of all types of water
present whenever enteric pathogens are present
survives longer than hardiest enteric pathogen
does not reproduce in contaminated water
detected by highly specific test
test easy to do and sensitive
harmless to humans
its level in water reflects degree of fecal pollution

12. Two Commonly Used Indicators
coliforms
fecal streptococci
increasingly used to test brackish and marine water

13. Coliforms
facultative anaerobic, gram-negative, nonsporing, rod-shaped bacteria that ferment lactose with gas formation within 48 hours at 35°C
traditional method of detection is multiple-tube fermentation test

14. Figure 42.2

15. Other Tests for Indicator Organisms
membrane filtration technique
presence-absence (P-A) test
defined substrate tests
molecular analysis
flow cytometry
FISH
quantitative PCRs
microarrays

16. Membrane Filtration Technique
water passed through filter 
filter placed on surface of growth medium
incubate
count colonies
used to detect total coliforms, fecal streptococci, and fecal coliforms
from intestines of warm-blooded animals
detected by incubation at 44.5°C

17. Table 42.2

18. Presence-Absence Test
modification of MPN
uses larger water sample (100 ml)
sample added to lactose containing medium
contains pH indicator to detect acid production
based on assumption that no indicator organisms should be present in 100 ml of water
detects total coliforms and fecal coliforms

19. Defined Substrate Tests
tests for both total coliforms and E. coli; e.g., Colilert
100 ml sample added to medium containing ONPG and MUG
produces a fluorescent product
other indicator microorganisms are fecal enterococci
used for brackish and fresh water

20. Figure 42.3

21. Wastewater Treatment number of steps that are spatially segregated
decreases organic matter and number of microorganisms in human waste-impacted water
has lead to major reduction in spread of pathogens

22. Table 42.3

23. Figure 42.4

24. Table 42.4

25. Wastewater Treatment Processes
primary treatment
removes solid material and forms sludge
secondary treatment
dissolved organic matter transformed into microbial biomass and carbon dioxide
forms stable floc – settles well
bulking sludge – does not settle properly
activated sludge system
horizontal flow of materials with recycling of sludge

26. Table 42.5

27. Figure 42.5

28. Wastewater Treatment Processes
tricking filter
waste effluent is passed over rocks or other solid materials upon which microbial biofilms have developed, and the community degrades the organic waste
extended aeration
reduces amount of sludge produced by using microbial biomass for energy requirements

29. Figure 42.6

30. Anaerobic Digestion
often sludges from aerobic sewage treatment, together with materials settled out in primary treatment are further treated by anaerobic digestion
reduces the amount of sludge for disposal
produces methane

31. Table 42.6

32. Wastewater Treatment Processes…
tertiary treatment
removal of nitrogen and phosphorus that may promote eutrophication
removes heavy metals, biodegradable organics, and remaining microbes, including microbes
constructed wetlands
employed in treatment of liquid wastes and for bioremediation

33. Figure 42.7

34. Home Treatment Systems
groundwater
water in gravel beds and fractured rocks below surface soil
microbiological processes in groundwater are not well understood
septic tanks for sewage
frequently fail to work properly, contributing to groundwater contamination

35. Figure 42.8

36. Biodegradation and Bioremediation by Natural Communities
metabolic activities of microbes can be exploited in natural environments
where physical and nutritional conditions for growth cannot be controlled
a largely unknown microbial community is present

37. Biodegradation and Bioremediation Processes
examples
use of microbial communities to carry out biodegradation, bioremediation, and environmental maintenance processes
addition of microbes to soils or plants for the improvement of crop production

38. Biodegradation biodegradation has at least three definitions
minor changes
fragmentation
mineralization

39. Figure 42.9

40. Bioremediation
the use of microbes to transform toxic molecules to nontoxic degradation products
the degradation of toxic molecules requires several stages, usually performed by different microbes
reductive dehalogenation
removal of a halogen substituent while at the same time adding electrons to the molecule
usually occurs under anaerobic conditions

41. Figure 42.10

42. Fate of a Chemical in Nature
structure and stereochemistry play critical role in predicting the fate of specific chemical
meta effect occurs when constituent is in meta, as opposed to ortho position, the compound will be degraded at a slower rate
many compounds added to environments are chiral
possess asymmetry and handedness
microbes often can degrade only one isomer of a substance; the other isomer will remain in the environment

43. Figure 42.11

44. Fate of a Chemical in Nature…
microbial communities change their characteristics in response to addition of inorganic or organic chemicals
acclimation
occurs if chemical is repeatedly added, the community adapts and faster rates of degradation occur

45. Downside of Biodegradation
can lead to widespread damages and financial losses if occurs in inappropriate situation or in an uncontrolled manner
e.g., corrosion of metals, especially iron pipes, toxic degradation products

46. Figure 42.12

47. Stimulating Biodegradation
bioremediation usually involves stimulating degradative activities of microbes already present at contaminated sites
it is necessary to determine the limiting factors at the site (e.g., nitrogen or phosphorus or other nutrients) and supply them or modify the environment
cometabolism
addition of easily metabolized organic matter increases degradation of recalcitrant compounds that are not usually used as carbon or energy sources

48. Some Examples
stimulation of hydrocarbon degradation in water and solids
phytoremediation
use of plants
stimulation of bioleaching of metals from minerals

49. Figure 42.13

50. Figure 42.14

51. Bioaugmentation
addition of microorganisms to complex microbial communities
generally has resulted in only short-term increases in desired degradative activity
outcome can be improved by providing protective microhabitats
living microhabitats (e.g., surface of a seed, root, or leaf)
inert microhabitats (e.g., microporous glass)
natural attenuation
use of natural microbial communities to carry out biodegradative process