How Does The Sewer Work?

Answer 1

Sewer systems work by gravity flow. This means that the pipes have to have a certain slope to them usually 1' drop per 100' length of pipe, in order for them to be self-cleaning (no build-up of waste). Also taken into consideration is the amount of flow each pipe is supposed to carry. As more and more pipes come together with more and more sewage volume, larger pipes are used until the sewage collects in what are called trunk sewers. Trunk sewers are generally any pipe 18" and over. Some get as large as 96"+.

Sometimes it is necessary to use pump stations to lift sewage from low points to high points where gravity can take over again.

Once the sewage has been collected at a treatment plant, the bulk of the water and solids are separated in a series of sedimentation ponds, with the water going through further treatment to remove pollutants before being put back into a river or the ocean, and the solids going into digester tanks where bacteria work on the different materials and turn it into a product called "sludge."

The sludge is then pumped, or trucked, to areas where it is spread out and allowed to dry and then either disposed of in dumps or further treated to be used as fertilizer.

Answer 2

There are three main types of sewers. You have a couple of answers describing sanitary sewage, so I'll skip that. There are also storm sewers, that carry rainwater plus whatever the rain washes in from the streets and lawns, plus what lazy people drop or pour into the inlets. The water, contaminated by nutrients, pesticides, oils, antifreeze, and the like, travels by gravity feed to the nearest body of water. There is no treatment from street to stream. If the stream feeds a drinking water plant, the water is treated there.

The third type of sewer is the combined sewer, carrying both rainwater and sanitary seweage. Because sewage treatment plants cannot handle the volume of mixed sewage after a heavy rain or snow-melt, the treatment plant operators release untreated or partially-treated sewage into the stream that takes their effluent. Urban planners have been avoiding telling municipalities to build combined sewers for many years. A lot of older municipalities still have them though.

Answer 3

It's just a huge network of pipes that flow gradually downhill (sometimes with a lift station here and there) to a treatment plant.

There it undergoes a few different processes. It goes through some grinders that break up big stuff like rags. It goes through some mesh filters to get out the big solids. These get dried and sent to the landfill. Then they add biological agents to break up the waste in an aerated tank. A chemical called a Flocculant is used to bind with some components of the waste and drop them to the bottom. Some of these solids are dried and used as fertilizer. Oils and greases are floated off the top. Then it undergoes chemical sanitizing agents to kill any leftover bugs, and it's released to a river or creek as surface water.

Answer 4

http://home.howstuffworks.com/home-improvement/plumbing/sewer3.htm