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Unit 8: Pollution: module 4.52 sewage treatment

MigrationSewage is anything coming from humans' (or animals') digestive system: 

  • urine (Nitrogen, salts) 
  • feces (nutrients and bacteria)

Bozeman Science:

https://elab.local/apes/videos/bozeman_science/

Water Pollution video:

http://www.bozemanscience.com/ap-es-030-water-pollution

Reference: FR4e Unit 8:

https://elab.hpa.edu/apes/texts/fr4e/unit%208%20water%20pollution.pdf

BOD: biochemical oxygen demand: the demand on the dissolved oxygen in progresswater needed to biodegrade the nutrients

Screenshot 2023-03-06 at 4.37.35 PM.png
Screenshot 2023-03-06 at 4.37.35 PM.png

Test for BOD: (white line on the graph above)

  1. take a sample from water
  2. measure DO (dissolved oxygen)
  3. store in dark place overnight (no photosynthesis)
  4. re-measure DO: if it drops, there were nutrients that needed to be biodegraded
  • If BOD is high, with no agitation or photosynthesis, it produces Dead Zones with very low DO
  • Why no agitation or photosynthesis?
  • Warm water or water with suspended solids make this worse (e.g. Chesapeake Bay)
Chesapeake Bay: Perfect storm of cultural eutrophication and dead zone
  • Phosphates from chicken manure: eutrophication, algal bloom
  • Nitrogen from fertilizer runoff and CAFO (concentrated animal feed operations): algal bloom
  • Silt from rivers: blocks photosynthesis, low DO
  • No agitation: low DO
  • Shallow and warm: low DO
  • High BOD from sewage: low DO
Disease organisms in sewage:
  • Cholera: simple bacteria, if you can remain hydrated, your immune system will cure you in a few days
  • Hepatitis: damages liver, can be fatal, several varieties (A, B, C) all contagious
  • Typhoid fever: waterborne, then airborne
  • Viruses: only killed by ozone treatment, not chlorine (!)
  • Fecal coliform: gut bacteria, harmless in your gut, toxic when on food or in water
  • Fecal coliform (FC) is an indicator of polluted water (see brown water alerts in Hawaii)
Sewage treatment: septic systems vs. cesspools
  • Septic system: tank for settling, leach field for absorption into soil, plants use the nutrients (e.g. elab)
  • Puako issue: septic systems are not in place, they have cesspools, essentially a concrete tank with holes, which leak raw sewage into the ocean near the shore when the tide comes in. Cesspools are now illegal in Hawaii.
Sewage treatment plants: 
  1. Primary treatment: physical: settling, liquid separated
  2. Secondary treatment: biological: aerobic bacteria with aeration (e.g. paddles)
  3. Tertiary treatment: chemical: kill the bacteria and any pathogens
Screenshot 2023-03-22 at 11.41.18 AM.png
Screenshot 2023-03-22 at 11.41.18 AM.png

Human health and LD50:

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