Environmental Engineering: Fundamentals and Design - Chapter 9

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TOC > Ch. 9 > 9.4 Water distribution

# Chapter 9 Water Supply, Distribution and Wastewater Collection

Brian E. Whitman and James R. Mihelcic

## Water distribution and wastewater collection systems

### Drinking Water Distribution

Pumping of the clean water produced at the treatment plant to the community is called distribution. This can be done directly or by first pumping the water to reservoirs or water storage tanks. If the water is stored on a hill, it can flow by gravity to the people.
| At left, a drinking water storage tank in Houghton, Michigan. At right, a water distribution plant for a housing subdivision. |

### Where Does It Go When I Flush The Toilet?

Wastewater is carried to the treatment plant via sanitary sewers. The connection from the house to the sewer system is a pipe, about 6â€ in diameter. A larger pipe (8-12â€ in diameter), called a collecting sewer, runs down the street picking up the wastewater from individual sewers. These pipes eventually run to an interceptor sewer which delivers the flow to the treatment plant. In large cities, interceptor sewers can be huge, sometimes big enough to drive a car through! Engineers design sewer systems to take advantage of gravity flow, but sometimes pumping is required.

Rainwater is collected by storm drains and flow through storm sewers to settling ponds or lakes and rivers.

### Combined and Separate Sewers

In older cities, the sewers carry both wastewater and rainwater that runs off of the streets. These are called combined sewers. During heavy rain events, the flow in combined sewers can reach capacity and threaten to back up into your house. To prevent this, relief structures called combined sewer overflows (CSOs) are constructed sending the excess water into streams, lakes and harbors. CSOs can grossly pollute rivers and lakes and thus efforts are being made to limit their discharge. Today, separate sewers are installed, with rain runoff discharge to surface waters via storm sewers and wastewater routed to the treatment plant with no discharge en route.

See how the city of Milwaukee uses deep tunnels
to store and later treat rainwater and wastewater from combined sewers.

#### Credits

Drinking Water Storage Tank photo: Andrew Whaley (Michigan Tech).
Water Distribution photo: Marty Auer.
Combined Sewer System animation: © 2007 State of Michigan.
Combined Sewer Overflow photo: Marty Auer.

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