11.7 Wastewater Treatment

Part One : Define the following:

Sewer system – series of underground pipes that carry used water to a treatment plant

Wastewater – any water that has been contaminated by people

(from homes, businesses, schools)

Blackwater – water that contains feces (solid waste/poop) and urine (pee)

Greywater – water used for cooking, bathing, laundry, or similar tasks

Stormwater runoff – water from precipitation (rain, snow) that runs off roofs, lawns or paved areas

Septic system – method of water treatment using your own property

(septic tank and drainage bed)

Question : What happens to the liquid inside a septic tank? (Think about layers)

As the liquid sits in the tank it separates into three layers.

Grease and scum float on top, liquid in the middle and sludge (solids/sediments)

forms on the bottom

Question : What are the two options cities have in dealing with stormwater?

The stormwater can go:

(1) directly to the water treatment plant and get treated or

(2)can go back into rivers and lakes (uncleaned).

This means that the water may go back into lakes and rivers contaminated.

Question : What types of contaminants can be found in stormwater runoff?

Stormwater runoff can contain road salt, pesticides, animal waste and other contaminants.

Question : What are three (3) possible destinations for solids removed from wastewater?

1. Landfill2. Incinerated (burned)3. Used as fertilizer

Part Two : Jot Notes

Waterwater Treatment Process

1. Preliminary Treatment

- water is filtered using a bar screen (removes sticks, rocks, garbage)

- water enters a grit tank and large sediment settles

- anything blocked by the screen or that settles in the tank is sent to a landfill

2, Primary Treatment

- water enters a settling tank

- more solid particles settle to the bottom

3. Secondary Treatment

- add in bacteria to eat organic matter

- oxygen is added to make bacteria grow

- extra solids sink to the bottom

4. Final Treatment

- add chlorine to kill bacteria that was added

- water is released in to the lake

5. Solids Processing

- solids are sent to the digester where micro-organisms digest the solids

- the solids become methane gas that can be used to burn or produce electricity

- bio-solids remaining go to the landfill, are incinerated or used as fertilizer

The Septic System

1. Septic Tank

- first stage where solids are trapped and digested by bacteria,

removing much of the harmful waste

- the treated liquid later flows into the drainage bed

2. Drainage Bed

- liquid flows into a set of pipes with small holes in them

- the liquid flows out of the holes into the soil and is absorbed