Negative Effects of Untreated Raw Sewage

• Odor
• Cholera (and other diseases) -flies & rodents transmitting.
• Eutrophication (through water ways)

The Septic Tank - Domestic Treatment

Inner Workings of the Septic Tank

1. When the toilet/water closet is flushed, all the sewage is sent to an in ground septic tank.
2. This tank has a wall separating it into two sections.
3. The sewage falls on one side.
4. As the capacity rises on one side, it eventually reaches to the top of the wall where water (Liquid) falls on the other side.
5. The side with the solids are broken down by bacteria which receives oxygen from from a pipe with an opening that is higher up on your house. This opening also allows all harmful gases to escape into the atmosphere.
6. Eventually water levels on the other side reaches a height where it is flown into a pipe in a ruble drain which disposes the water into the soil.

Large Scale Sewage Treatment

1. Screening - Where large particles are removed, for example: plastic bottles, paper, sticks etc.
2. Grit Pit - Slowly passes the sewage allowing the grit to settle.
3. Sedimentation - Where solids (sludge) is allowed to settle. The sludge is either sent to a sludge digester.
4. Aeration - Implementing air for bacteria to breakdown sewage.
5. Effluent is then disposed.

What happens if Untreated Sewage is released into Waters?

• This provides a source of food for bacteria which multiply rapidly and breaks down the sewage.
• This vast amounts of bacteria will use up oxygen supply which then kills other living organisms.
• When these organisms die, the process repeats as bacteria break them down.
• They continue to multiply.

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