Water Pollutants and their Sources

1. Water Pollutants and their
Sources

3. River and Lake Pollutants
• Sewage, manure
nitrogen, phosphorus
pathogenic organisms
biodegradable chemicals – consume O2
• Fertilizers
nitrogen, phosphorus
• Pesticides, oil
• Toxic chemicals
• Sediments

4. Effects of Pollutants
• Oxygen depletion
– septic
conditions
– change in biota
– destruction of
certain species
• Biomagnification
– Restrictions on
fish
consumption
• Accumulation in
sediments (benthic
organisms)
– more turbid
waters
– loss of habitats
– clog fish gills
– change in biota
• Foaming

5. Point sources
• Wastes that are collected in pipes or
channels and discharged to a surface water
with or without treatment
• Distinguished by source
– municipal sewage or wastewater
– industrial waste waters
– combined sewers and combined sewer
overflows

6. Non-point sources
• Storm water runoff discharged at multiple
points
• Varies substantially with use of the land
runoff originates from
– agricultural
– urban
– suburban
– commercial
– special (e.g. golf courses)
• Minimal regulation

7. Oxygen-Demanding Material
• When organic substances are broken down
in water, oxygen is consumed
organic C + O2 → CO2
• High oxygen levels necessary for healthy
stream ecology
– trout require 5-8 mg/L dissolved
oxygen (DO)
– carp require 3 mg/L DO
– aesthetic problem <1 mg/L

8. Oxygen-Demanding Material
• Pollutants measured by oxygen demand potential
or total organic content
– biochemical oxygen demand (BOD)
– chemical oxygen demand (COD)
– total organic carbon (TOC)
• Sources
– municipal sewage -- agricultural wastes
– storm water -- leachate
– industrial wastes (e.g. pulp and paper, food
processing, chemical processing)

9. Nutrients
• Phosphorus is typically the limiting nutrient in
lakes, and algae growth is linked to
phosphorus inputs
• Problems
– aesthetics
– taste and odor in drinking water
– can be toxic, especially to farm animals
– Disturbance in DO cycles

10. Nutrients
• Phosphorous Sources
– fertilizers
– detergents
• Phosphorous can exist in a variety of
chemical forms, so total P in normally
measured

11. Nutrients
• Nitrogen is often the limiting nutrient in
ocean waters and some streams
• Nitrogen can exist in numerous forms, but
nitrate (NO3
-), nitrite (NO2
-), ammonia
(NH3) are most commonly measured
• Sources are primarily from fertilizers and
acid deposition

12. Salts
• Dissolved solids, or salts, may be present as
any number of ions
– cations: Na+, K+, Mg2+, Ca2+
– anions: Cl-, SO4
2-, HCO3
-
• Typically measures as total dissolved solids
(TDS)
• Water classification
– freshwater <1500 mg/L TDS
– brackish water 1500 – 5000 mg/L
– saline water >5000 mg/L
– sea water 30-34 g/L

13. Salts
• Sources and concentration influences
– minerals
– evaporative losses
– irrigation
– industrial discharges
– sea water intrusion
• Effects
– limits use for drinking
– crop damage/soil poisoning

14. Suspended Solids
• Organic and inorganic particles in water are
termed suspended solids
• May be distinguished from colloids,
particles that do not settle readily
• Measured by filtering a water sample,
drying and weighing the filter

15. Suspended Solids
• Problems
– sedimentation
– may exert oxygen demand
– primary transport mechanism for many
metals, organics and pathogens
– aesthetic
– complicates drinking water treatment
• Sources
– storm water
– wastes
– erosion

16. Pathogenic Organisms
• Many organisms that cause human or
animal diseases colonize the intestinal tract
but can live for a period of time outside the
body
• Carriers (who may or may not exhibit
disease symptoms) excrete these intestinal
tract organisms in very large numbers
• When water is contaminated by excreta, the
organisms can be transmitted to those who
contact the water

17. Pathogenic Organisms

18. Pathogenic Organisms

19. Toxic and Hazardous
Substances
• Volatile organic
compounds
• Petroleum Additives
• Pesticides
• Heavy metals
• Other inorganic
elements
• Acids/bases
• Oxidants/reductants
• Chlorination by-
products
• Combustion by-
products

20. Volatile Organic Compounds
• Petroleum constituents:
–benzene and substituted benzenes
–prevalent in gasoline, diesel fuel,
heating oil
–most easily transported, slow
degradation, toxic
CH2CH3
CH3 CH3
CH3
Benzene Toluene Ethylbenzene m-Xylene

21. Volatile Organic Compounds
• Oxygenated gasoline additives
–added to gasoline to improve air quality
–very soluble, resistant to degradation,
toxic
–attempt to solve one problem caused
another (spills)
CH3 C
CH3
CH3
O CH3 Methyl tertiary butyl ether (MTBE)

22. Volatile Organic Compounds
• Chlorinated solvents
– C1 and C2 aliphatic
– widely used in degreasing, dry cleaning,
extraction
– somewhat soluble, volatile, difficult to
degrade
C
Cl
Cl
Cl
Cl C
Cl
Cl
Cl
H C C
Cl
Cl
Cl
H
H
H
C C
H
H
Cl
H
carbon tetrachloride chloroform 1,1,1-trichloroethane vinylchloride

23. Hydrophobic Organics/
Chlorinated Aromatics
• Chlorinated Pesticides
• Polychlorinated dibenzodioxins (PCDDs)
• Polychlorinated biphenyls (PCBs)
O
O
Cl
Cl
Cl Cl
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
Biphenyl
Cl
Cl
Cl
2,3',4-trichlorobiphenyl

24. Some Other Categories
• Trihalomethanes
• Explosives and Propellants
• Phenolics
• Aldehydes
• Organometallics
• Asbestos

25. Arsenic
• Occurs naturally in rock and soil
• Released to groundwater under some
conditions
• Health effects include skin cancer, nervous
system effects, and kidney disease
• Major problem in Bangladesh