Water Pollutants

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Water Pollutants
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Water Pollutants

• Pathogens
• Broad Street well
• London Dr John Snow

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Water Pollutants

• Pathogens
• Virus
• Hepatitis A. infectious hepatitis
• Adenoviruses . Respiratory, eye infections
• Enteroviruses. Polio, meningitis

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Water Pollutants

• Pathogens
• Bacterium
• Salmonella typhi
• Vibrio cholerae
• Shigella

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Water Pollutants

• Pathogens
• Protozoan
• Giardia lamblia. diarrhea
• Cryptosporidium . Diarrhea
• Entamoeba histolytica . Amoebic dysentery

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Water Pollutants

• Pathogens
• Helminth
• Necator americanus - hookworm
• Ascaris - roundworm
• Table 5.4

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• Pathogens
• Waterborne - oral ingestion of pathogens
  contaminated by urine and feces - cholera,
  typhoid, infectious hepatitis

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• Pathogens
• Water-washed - disease spread enhanced by
  scarcity of water making cleanliness difficult -
  trachoma, dysentary

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• Pathogens
• Water-based - water provides habitat for
  intermediate host organisms transmission to
  humans thru water contact - schistosomiasis

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• Pathogens
• Water-related - insect vectors (e.g., mosquitoes)
  rely on water for habitat but human water-contact
  not needed - malaria, yellow fever, dengue

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Global Implications (T5.6)

• Diarrheal diseases - microbes mortality 4
  million pop. at risk gt2 billion
• Malaria - mosquitoes mortality 1-2 million
  pop. at risk 2.1 billion
• Schistosomiasis - water snails mortality 1-2
  million pop. At risk 600 million

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Water Pollutants

• Pathogens
• Indicator organism
• easy to detect
• always present when pathogens present
• present in high numbers
• more persistent then pathogens
• Escherichia coli - E.coli
• Coliforms

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Water Pollutants

• Oxygen-demanding wastes
• Oxygen dissolved in water is critical to
  maintaining fish population levels of minimum
  DO is fish-population dependent

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Water Pollutants

• Oxygen-demanding wastes
• ThOD
• Biochemical Oxygen Demand
• BODult BOD5day
• Chemical Oxygen Demand
• COD

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Water Pollutants

• Nutrients
• Nitrogen
• Organic-N, N2, NH4, NO3
• Deamination, nitrification, denitrification,
  protein-synthesis
• Nitrogen cycle
• Methemoglobinemia

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Water Pollutants

• Nutrients
• Phosphorus
• Organic-P, PO4-3 (etc.)

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Water Pollutants

• Salts - TDS
• Thermal pollution - increase temperature

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Water Pollutants

• Salts - TDS
• Thermal pollution - increase temperature
• Heavy metals
• Pesticides

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Water Pollutants

• Salts - TDS
• Thermal pollution - increase temperature
• Heavy metals
• Pesticides
• VOCs
• PCE,TCE, DCE, VC, ethane

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BOD

• Degradation of organic matter in nature
• Bacteria mediate oxidation of biodegradable
  organics inorganics
• Oxygen is critical to oxidation and is the final
  electron acceptor

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BOD

• Degradation of organic matter in nature
• Bacteria mediate oxidation of biodegradable
  organics inorganics
• Oxygen is critical to oxidation and is the final
  electron acceptor

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BOD

• W/o oxygen, fermentation reactions occur and
  reduced end products are generated (methane,
  volatile acids)
• W/o oxygen, degradation of organic matter under
  anaerobic conditions results in (i) changes in
  chemical composition (i.e., individual organics
  present) BUT (ii) no change in the level of
  reducing power or BOD present!

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BOD

• So, BOD bioassay is an excellent means of
  measuring the level of biodegradable organic
  matter under fully aerobic conditions.
• Since objective is to always maintain aerobic
  conditions in streams, this is a reasonable
  limitation for the bioassay and it is routinely
  used to measure organic strength of waters,
  wastewaters, and stream lake systems

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BOD

• Measurement is done with a bioassay
• Microbial population - SEED
• Dilution water w/ oxygen (usually saturated with
  DO (20C, 9.2mg/L) and all essential (non-organic)
  nutrients (N, P, trace metals)
• Organic-waste containing water - SAMPLE
• Bioassay premise is biodegradable organic matter
  is the limiting nutrient

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BOD

• Measurement is done with a bioassay
• Microbial population - SEED
• Dilution water w/ oxygen and essential nutrients
  (N, P, trace metals)
• Organic-waste containing water - SAMPLE

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BOD

• Measurement is done with a bioassay
• Microbial population - SEED
• Dilution water w/ oxygen and essential nutrients
  (N, P, trace metals)
• Organic-waste containing water - SAMPLE
• Premise is that carbonaceous organic matter is
  the single limiting-nutrient and dissolved oxygen
  is used to monitor degradation of organic matter

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BOD Dilution Water

• If BOD of raw sample is greater then 9 mg/L
  (i.e., DO saturation level), waste sample must be
  diluted because all O2 would be consumed and
  organic (I.e., BOD) would still remain in the
  sample.

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BOD Dilution Water

• Dilution levels are complex to predict since
  initially BOD is unknown.
• Typical practice is to make dilutions at 3 to 4
  levels (e.g., 1/10, 1/100, 1/1000) so that a
  positive result is achieved 5 days later (I.e.,
  BOD5).

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BOD

• P dilution factor
• (volume of sample)/(volume of sample
  dilution water typically 300mL)

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BOD

• P dilution factor
• (volume of sample)/(volume of sample
  dilution water typically 300mL)
• Period of test is typically 5 DAYS

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BOD

• P dilution factor
• (volume of sample)/(volume of sample
  dilution water typically 300mL)
• Period of test is typically 5 DAYS
• BOD calculation for unseeded sample
• BOD5 (DOinitial - DO5days)/P

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BOD

• Blanks are used to test level of organic matter
  in dilution water
• BOD for seeded sample using a series of blanks
  (i.e., B dilution water w/o organic matter)
• BOD5 (DOinitial - DO5days)/P - (Binitial-
  B5days)(1-P)/P
• (see example 5.2)

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BOD model

• Carbonaceous organic matter is
• limiting nutrient
• measured in terms of oxygen equivalents, mg/L as
  O2
• Aerobic conditions prevail

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BOD model

• BOD reaction is a first-order decomposition in a
  batch reactor of fixed volume, limited only by
  organic matter (i.e., all nutrients are available
  to bacteria in excess)

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BOD model

• L oxygen demand
• carbonaceous organic matter measured in
  oxygen equivalents, mg/L as O2
• Lt carbonaceous oxygen demand remaining
  after time, t
• k BOD reaction rate constant, (time)-1

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BOD model

• dLt/dt - kLt
• Lt L0 e-kt
• L0 ULTIMATE carbonaceous BOD
• L0 (BOD)t Lt

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BOD model

• dLt/dt - kLt
• Lt L0 e-kt
• L0 ULTIMATE carbonaceous BOD
• L0 (BOD)t Lt
• (BOD)t L0 Lt L0 1- exp(-kt)

L0
BODt
time
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BOD model

• BODt L0 (1- e-kt)
• kT k20 QT-20
• Qtypical value 1.047

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BOD

• Nitrogenous oxygen demand
• NH4 oxidation or
• Nitrification
• Bacterial decomposition of NH41
• NH4 2 O2 ? NO3-1 2H H2O
• 2 moles of O2 per mole of Nitrogen, as NH4-N,
  or
• 4.57mg of O2 per mg of NH41-N
• ALK consumption 100mg ALK as CaCO3 per 14 mg
  NH4-N (7.14mg ALK/mg NH4-N)

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• dD/dt (kdL) - (krD)
• Dt
• kdL0 /(kr - kd )exp(-kd t) - exp(-kr t) )
• D0 exp - kr t )