Sewage Systems: What They Are & Why They’re Important for Cities

Have you ever wondered what happens when things go down the drain?

Sewage systems were a normal addition to the rise of cities, going back almost 5,000 years. But people only tend to know the smelly running water side of these systems.

So today, we’ll tell you more about the basics of sewage systems — from the different kinds seen in cities and why they’re important.

What Is a Sewerage System?

A sewerage (or sewage) system is an infrastructure that collects wastewater and moves it to a treatment facility.

It’s a network made up of parts such as pipes and chambers.

Aside from wastewater, sewage systems can also carry storm water — which is surface water due to heavy rain or snow. This kind of water can be moved immediately for disposal since it doesn’t contain anything harmful.

Some systems carry BOTH wastewater and storm water. However, there are some that carry only either of the two.

The Different Sewerage Systems Used in Cities

Cities use different sewage systems for water to be safely transported from its point of origin to the facility.

We’ll talk about some of them below:

Drainage Systems

A drainage system consists of pipes that take sewage to a facility. These pipes are normally made of plastic or metal.

The way these systems work is that a drain line collects used water and waste from fixtures like toilets and tubs. These drain lines then rely on gravity to flow to the main drain system since they’re all plumbed at a slope.

There are also vent pipes attached to drain lines, which provide air pressure to keep the water flowing smoothly.

Meanwhile, traps in the drainpipe ensure that sewer gasses DON’T go back into the building. 

Drainage systems can come in two kinds:

• Closed drain - A closed drain is found underground, forming a complex network. This is where the drain pipes from different areas connect to.

• Open drain - This can be used for collecting storm water, since it’s extremely unhygienic to use for transporting domestic wastewater.

To properly maintain drainage systems, it’s important to check for clogged drains and sewer line breaks or leaks.

Pumping Stations

A pumping station lifts and moves wastewater when gravity can’t help — such as when the water needs to move in an upward incline or in a horizontal direction.

Pumping stations are typically made up of a tank/wet well, float switches, and one or two pumps. The whole thing can be operated by a control panel near the well.

The sewage water flows into the well, and when the water reaches a certain level, it activates the float switches. This will activate the pump, which will cause the water to move out of the well and back to the main sewer line.

Since pump stations have a lot of MECHANICAL parts, it’s important that they undergo regular maintenance. Perhaps one of the most common problems is the high amount of unflushable items that get caught in the pumps.

Manholes

Manholes are also known as maintenance holes. They’re vertical spaces used by utility personnel to access the sewerage system.

These systems are extremely helpful since they make it easy for responders to remedy any problem regarding the sewer pipes.

Beneath the manhole cover is a design that consists of a barrel, bench, and channel. The depth of a manhole can be anywhere from 2ft to more than 5ft deep.

Manholes are typically found where there’s a:

• Change in sewer line
• Change in sewer size and alignment
• Intersection formed by multiple sewers

But if a sewer pipe just runs in a straight line, then you can expect to see manholes every 260 to 330 feet.

Frequently Asked Questions

Sewage systems certainly help people live in cleaner communities.

Below, we’ve answered a few questions that can help you understand and appreciate these systems more:

Why Should We Have Sewage Systems?

The very first thing you should know (which you probably already know) is that sewage water is very smelly. That alone will make you NOT want to throw it just outside your house.

Another thing we should warn you about is that sewage water is harmful to you and the environment.

For one, human waste has coliform bacteria, such as E. coli, which is a huge health hazard.

Wastewater also has nitrogen and phosphates, which can cause EXCESSIVE algae growth. This will block sunlight and overpopulate any body of water, affecting the life forms in that water.

Sewage water also has organic material that will be decomposed by bacteria in the environment. 

If that wastewater has been thrown into another body of water, the bacteria will use the oxygen in the water. That can decrease the available oxygen supply for other life forms in the water.

What Happens to the Collected Wastewater?

The wastewater enters a treatment facility to undergo up to three stages of treatment:

• Primary treatment - The wastewater flows through a screen and several pools/ponds to let the water sit and solids settle.

• Secondary treatment - The water goes to big aerated tanks where bacteria can consume all the nutrients and organic materials they can.

• Tertiary treatment - Chemicals can be used to remove phosphorus and nitrogen from the water. Chlorine is also added to kill the bacteria. It’s also possible to use filter beds and other forms of treatment.

Is There Such a Thing as a Private Sewage System?

Sometimes, especially in rural areas, houses are spaced too far apart to the point where creating a sewerage system would be too expensive.

In such cases, each house can install its own private sewage system plants, called septic tanks. These concrete or steel tanks can hold up to 1,000 gallons of water and are buried in the yard. 

The way it works is that sewer water flows into one end and exits the other as it gets displaced by new water that enters.

This displaced water flows through a drain field pipe, which is buried in a trench filled with gravel.

From there, the water gets slowly absorbed and filtered in the drain field.

Final Words

Despite the many kinds of sewerage systems, they all have one thing in common — they help keep our communities clean and safe. 

These systems can do so by ensuring that wastewater is properly collected and transported from the point of origin to the treatment plant.

They also make sewer inspection and maintenance easier for the personnel involved.