Wastewater Treatment Flashcards

1
Q

Why is drinking water treated?

A

to remove insoluble material, microorganisms, organic/inorganic compounds, and to prevent growth of new microorganisms

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2
Q

How is drinking water treated?

A
  • coagulation: form and remove floc containing insoluble material and microorganisms
  • filtration: removing remaining particulates and most organic and inorganic compounds
  • chlorination: kills remaining microorganisms and prevents growth of new inocula
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3
Q

What are the goals of wastewater treatment?

A
  • preventing waterborne disease (typhoid fever, cholera, protozoan infections)
  • preventing pollution and dead zones
  • keeping water clean and safe to swim in (tourism)
  • keeping water clean for downstream users
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4
Q

What is BOD?

A
  • stands for biological oxygen demand
  • measures how much oxygen it takes for the bacteria to break down organic compounds
  • an indirect measure of the amount of organic matter in the water
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5
Q

What are clarifiers?

A
  • used to remove solid particulates or suspended solids from the water
  • water is allowed to settle in tanks
  • involved in primary wastewater treatment
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6
Q

What is sludge?

A
  • a byproduct of wastewater treatment
  • mix of organic matter, microorganisms, trace chemicals, and inorganic solids
  • disposed of after each step of treatment
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7
Q

What is floc?

A
  • flakes of material in the water
  • forms globs to that it can be more easily removed
  • normal floc settles well
  • bulking sludge does not settle properly
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8
Q

What happens in primary wastewater treatment?

A
  • physical processes
  • uses grates and screens to remove solid particles
  • water is allowed to settle in tanks (clarifiers)
  • effluent still has a substantial BOD
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9
Q

What happens in secondary wastewater treatment?

A
  • water from primary clarifier moves into an aeration basin
  • mixers are used to aerate the water
  • organic matter in the water is processed by suspended biomass
  • the final clarifier removes the bacteria and sludge
  • activated sludge and biomass is returned to the aeration basin
  • waste sludge is disposed of
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10
Q

What happens in tertiary wastewater treatment (nitrogen removal)?

A
  • nitrogen is present in sewage as ammonia (NH3)
  • nitrosomonas and nitrobacter convert ammonia (NH3) to nitrate (NO3) in an aeration basin (nitrification, step 1)
  • nitrification consumes a great deal of oxygen
  • bacteria convert nitrate (NO3) to N2 gas in an anoxic basin (denitrification, step 2)
  • nitrate (NO3) from the aeration basin is recycled back to the anoxic basin
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11
Q

What happens in tertiary wastewater treatment (phosphorus removal)?

A
  • a group of bacteria called PAOs (phosphorus accumulating organisms) removes phosphorus under the appropriate conditions
  • bacteria is cycled between anaerobic and aerobic conditions
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12
Q

How are coliforms detected in water?

A
  • coliforms are indicators of microorganisms in water
  • standard method: add water to MacConkey broth and gas tube, plate on EMB agar, plate on nutrient agar slant, Gram stain
  • membrane filter: see if colonies form on the plate through the filter, takes about 1 day to get the results
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13
Q

What is the purpose of anaerobic digestion?

A
  • used for high BOD industrial wastewater
  • reduces amount of sludge for disposal
  • produces methane
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