Chapter 42

1. 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. 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 Membrane Filtration Technique

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