1. Water pollution and its prevention
Chapter 17
Water pollution and its prevention

3. 1. Water pollution

4. What is water pollution
Water pollution can be defined as
"the presence of a substance in the environment that because of its chemical composition or quantity, prevents the functioning of natural processes and produces undesirable environmental and (human) health effects."

5. Categories of Water Pollutants

6. Main groups of water pollutants
Biodegradable
Rapidly degradable (non-persistent)
Slowly degradable (persistent)
Non-biodegradable

7. Water Pollutants: sources
a. Non-pont-source pollutants: agricultural runoff, storm-water drainage, atmospheric deposition. b. Point-source pollutants: discharges from factories, sewage systems, power plants, underground coal mines, oil wells.

8. Strategies to bring water pollution under control:
Reduce or remove the sources
Treat the water to remove pollutants or convert them to harmless forms.

9. Water pollutants: types
a. Pathogens b. Organic wastes c. Chemical pollutants d. Sediments e. Nutrients

10. Pathogens Infectious agents that cause sickness and death
Come from excrement from humans and other animals that are infected
Disease
Infectious Agent
Typhoid fever
Salmonella typhi (bacterium)
Cholera
Vibrio cholerae (bacterium)
Salmonellosis
Salmonella sp. (bacteria)
Diarrhea
Echerichia coli,
Campylobacter sp. (bacteria)
Cryptosporidium pavum (protozoan)
Infectious hepatitis
Hepatitis A virus
Poliomyelitis
Poliovirus
Dysentery
Shigella sp. (bacteria)
Entamoeba histolytica (protozoan)
Giardiasis
Giardia intestinales (protozoan)
Numerous parasitic diseases
(Roundworms, flatworms)

11. Public heath
Before mid 1800s: epidemics were common in cities (typhoid fever, cholera)
After: connection between disease and sewage-carried pathogens
Today: public health measures
Purification and disinfection of public water supplies with chlorine and other agents
Sanitary collection and treatment of sewage wastes
Maintenance of sanitary standards in all facilities in which food is processed or prepared for public consumption
Public education in personal and domestic hygiene practices

12. Sanitation = good medicine
Good health is a result of the prevention of disease through public-health measures
Population in areas where here is little or no sewage treatment are extremely vulnerable to deadly epidemics.

13. Organic wastes Includes leaves, grass clippings, trash, etc.
Enter water as a consequence of runoff or excessive aquatic plant growth
As bacteria and detritus feeders decompose organic matter, they consume O2 dissolved in water.
BOD (biochemical oxygen demand): measures the amount of organic material in water in terms of how much oxygen will be required to break it down.
Fishes and shellfish are killed at an OD of 2 to 3 ppm
A BOD value for raw sewage is around 250 ppm

14. Chemical pollutants
Inorganic chemicals: include heavy metals (lead, mercury, cadmium, nickel, etc), acids from mine drainage and acid precipitation, and road salts.
Organic chemicals: include petroleum products, pesticides, industrial chemicals (PolyChorinated Biphenyls, cleaning solvents and detergents)

15. Sediments
Erosion from farmlands, deforested slopes, overgrazed rangelands, construction sites, mining sites, stream banks and roads increase the load of sediments.

16. Nutrients
Inorganic chemicals carried in solution in all bodies of water are classified as nutrients.
Include phosphorus and nitrogen
Stimulate undesirable plant growth in the bodies of water.
Sources include sewage outfalls, agricultural runoff, lawns and gardens, golf courses and storm drains.

17. Water quality standards
National Recommended Water Quality Criteria (EPA) provides standards for assessing water pollution.
Lists 158 chemicals and substances as criteria pollutants and recommends concentrations for fresh water, salt water and human consumption

18. Water quality standards
Criteria maximum concentration (CMC): highest single concentration beyond which environmental impacts may be expected
Criterion continuous concentration (CCC): highest sustained concentration beyond which undesirable impacts may be expected
Drinking water standards and health advisories: enforceable under the authority of the Safe Drinking Water Act (SDWA)
Maximum Contaminant levels (MCLs)

19. Arsenic as a example: Listed as a human carcinogen
CMC and CCC values are 340 and 150 g/L for freshwater bodies, and 69 and 36 g/L for saltbodies.
Drinking water MCL concentration is 10 g/L

20. Other applications to the water quality criteria
National pollution discharge elimination system program (NPDES): addresses point-source pollution and issues permits to regulate discharges from industrial sources.
Total maximum daily load program(TMDL): evaluates all sources of pollutants entering a body of water, especially non-point sources

21. 2. Eutrophication

22. Types of aquatic plants
Benthic
Submerged aquatic vegetation (SAV)
Emergent vegetation
Phytoplankton (algae, protists, cyanobacteria

23. What is an oligo-trophic body of water?
Oligotrophic = low in nutrients

24. What is a Eutrophic Body of Water?
Eutrophic = well nourished

25. How do you create a Eutrophic Body of Water?
1. Nutrient enrichment, natural or cultural
2. Increased phytoplankton growth resulting in increased turbidity
3. Loss of sunlight, food and habitat
4. Depletion of dissolved oxygen from decomposition of phytoplankton by decomposers

26. How to Stop Eutrophication
Attack the symptoms:
Chemical treatments (with herbicides)
Aeration
Harvest aquatic weeds
Draw water down

27. How to Stop Eutrophication
Attack the root cause:
Control point-source pollutants
Ban the sale of phosphate detergents
Regulate the maximum alowable level of phosphates
NPDES permits

28. How to Stop Eutrophication
Attack the root cause:
Control non-point-source pollutants
EPA regulations through the TMDL program include:
Identify pollutants
Estimate pollution comming from all sources
Estimate the ability of the body of water to assimilate pollutants
Determine the maximum allowable pollution load
Allocate the allowable level of pollution among the different sources

29. How to Stop Eutrophication
Attack the root cause:
Best management practices (BMPs)
Practices used to minimize erosion, runoff and leaching
Methods of soil conservation

30. When washings from animal facilities are flushed directly into natural waterways, they contribute significantly to eutrophication. This may be avoided by collecting the flushings in ponds from which both the water and the nutrients may be recycled.

31. How to Stop Eutrophication
Attack the root cause:
Recovery
Govenrment practices for the management of watersheds
Lake washington

32. 3. Sewage Management and Treatment

33. History of sewage treatment
Late 1800s: human excrement was disposed in the outdoor privy
Louis Pasteur and other scientists showed that sewage borne bacteria were responsible for many infectious diseases
Human wastes started to be disposed through drain systems
The flush toilet was introduced
Water became unfit to swim in because of sewage contamination
1900: Sewage treatment systems were developed

34. What is in Raw Sewage
1. Debris and grit: plastic bags, coarse sand, gravel
2. Particulate organic matter: fecal matter, food wastes, garbage, toilet paper
3. Colloidal and dissolved organic matter: urine, soaps, detergents and cleaning agents.
4. Dissolved inorganic matter: nitrogen, phosphorus, and other nutrients
5. Pathogens: bacteria, protozoa, virus
6. Heavy metals, pesticides, and various other toxic compounds

35. How Do We Remove These Substances from the Water?
Preliminary Treatment - debris and grit removed by a bar screen and grit chamber

36. How Do We Remove These Substances from the Water?
Primary Treatment - particulate organic matter removed by primary clarifiers

37. How Do We Remove These Substances from the Water?
Secondary Treatments - colloidal and dissolved inorganic matter removed by trickling filter systems or activated sludge systems

38. How Do We Remove These Substances from the Water?
Biological Nutrient Removal - dissolved inorganic matter removed by bacterial denitrification and bacterial uptake of phosphorus a. Can also be done inorganically by using chemical processes ·Lime causes phosphate to precipitate as insoluble calcium phosphate ·Ferric chloride causes phosphate to precipitate as insoluble ferric phosphate b. Removal of the dissolved inorganic matter is not standard treatment though it is becoming more common

39. Final Clarification and Disinfection
Meant to eliminate pathogens
Disinfecting agents
chlorine gas
Sodium hypochlorite (chlorox)
Ozone gas
Ultraviolet light

40. Discharge BOD values are 10 to 20 ppm (200 ppm in the incoming sewage)
Many cities are still operating with lower quality treatments or with no treatment at all.

41. Treatment of sludge Raw sludge
Most is disposed in landfills with no previous treatment
It is considered a biologically hazardous material
It is a nutrient-rich organic material with potential to be used as organic fertilizer
Methods for treating sludge include:
Anaerobic digestion
Composting
Pasteurization

42. Anaerobic digestion
Raw sludge is put into large airtight tanks (sludge digesters)
Anaerobic bacteria break down the organic matter
End products include carbon dioxide, methane and water (biogas)
Treated sludge is called biosolid
Dewatered it becomes a sludge cake

43. Composting Raw sludge is mixed with wood chips
Placed in piles that allow air circulation
Aerobic bacteria and other decomposers break down organic material to rick humus-like material

44. Pasteurization The sludge cake is put through ovens to be pasteurized
The product is dry, odorless organic pellets.

45. Alternative Treatment Systems
On site wastewater treatment systems
Using effluents for irrigation
Reconstructed wetland systems

46. 4. Public Policy

47. Public Policy EPA is responsible for overseeing water
Depends on laws passed by Congress
Clean water act (CWA) of 1972
Required permits for all point source discharges of pollutants
Clean water state revolving fund program (SRF)
Gives funds to local governments to build treatment facilities

48. Problems and progress Problems Progress Non point source pollution
Construction of new wastewater treatment facilities
Storm water discharges
Sewer overflows
Wetlands protection
Animal feeding operations
Progress
The number of people served by adequate sewage has increased
Soil erosion has been reduced
Two-thirds of the nation’s waterways are safe for fishing and swimming
Many rivers have been cleaned up and restored