Unit 8: Pollution: module 4.52 sewage treatment

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

Bozeman Science:

Water Pollution video:

Reference: FR4e Unit 8:

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

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

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:

Human health and LD50:

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