Getting Down and Dirty: How Do Water Treatment Plants Work?

Wastewater treatment is one of the most common forms of pollution control in the United States of America. The United States a vast system of water treatment plants, pumping stations, and collection sewers.

Sewers collect wastewater from businesses, homes, and many industries. They then deliver the water to plants to be treated.

Many treatment plants were built to clean wastewater for discharge into bodies of water. Many years ago, a natural process of purification began when sewage was dumped into waterways. The large volume of clean water in the stream would dilute the waste.

The larger volumes of wastewater today require that communities be more proactive. The basic purpose of wastewater treatment is to speed up the natural processes by which water becomes purified.

There are two main stages during the treatment of wastewater – primary and secondary. The primary stage removes solids from wastewater. The secondary stage makes use of organic methods in order to make the water even purer.

Sometimes, these stages are combined.

If you’d like to learn the full down and dirty about water treatment plants, then keep on reading for more!

Primary Treatment

As sewage comes to the plant to be treated, it will flow through a screen. This screen will get rid of large floating objects, such as sticks and rags, that can clog up pipes or break equipment.

After the sewage has been screened, it will pass into a grit chamber. Here, small stones, sand, and cinders will settle to the bottom. A grit chamber is especially important in cities that have combined sewer systems where gravel or sand might wash into sewers along with stormwater.

Secondary Treatment

The majority of the organic matter in sewage will be removed during the secondary stage of treatment. It does this by utilizing the bacteria that’s in the sewage.

The main techniques in secondary treatment use are the activated sludge process and the trickling filter.

After the liquid waste leaves the sedimentation tank in the first stage, it will flow to a treatment plant that uses one of these two processes. A trickling filter is made out of a bed of rocks through which the sewage passes.

Bacteria will collect and grow on these stones until they eat most of the organic matter. The cleaner water will then trickle out through pipes to be treated further. From a trickling filter, the sewage will then flow to a different sedimentation tank in order to remove more bacteria.

These days, the trend is moving more towards using the activated sludge process instead of trickling filters. The activated sludge process speeds the work of the bacteria up by bringing air and sludge into close contact with sewage. After the sewage leaves the settling tank in the first stage, it’s pumped into an aeration tank.

Here, it’s mixed with sludge and air that’s full of bacteria. During this time, the bacteria will work to break the organic matter down into harmless byproducts.


In order to finish the secondary treatment, liquid waste from the sediment tank is typically disinfected with chlorine. This is done before it’s discharged into the waterways.

Chlorine is fed into the water in order to reduce odor and kill pathogenic bacteria. When it’s done correctly, chlorination will kill almost all of the dangerous bacteria in the waste.

Some cities now make their own chlorine solution so that don’t have to store and transports large amounts of chlorine. Many states also require that excess chlorine is removed before being discharged into the water. This process is known as dechlorination.

Other than using chlorine to disinfect, ozone and UV light can be used to treat water. There are also CaCl2 hazards (calcium chloride) hazards that municipalities need to be mindful of.

Other Treatment Options

Wastewater treatment plants have been seeing new pollution problems in recent years. Modern pollutants, such as toxic substances, chemical compounds, and heavy metals, are harder to get out of water.

Rising demands on the water supply are only exacerbating the issue. As people call to reuse more water, wastewater plants are trying to come up with more efficient systems.

These problems are being solved with better techniques for removing pollutants at treatment plants. Plants are also utilizing pretreatment, which removes pollutants at the start of the process instead of the end.

Biological treatments are being used to get rid of phosphorus and nitrogen. Chemical separation techniques are also being used to filter out toxins.

These processes can help to control increased pollution. They can work for recreational, agricultural, or industrial purposes. And they can even be used for clean drinking water.

The Importance of Knowing How Water Treatment Plants Work

Hopefully, after reading the above article, you now have a better idea of how water treatment plants work. As we can see, water treatment plants play a vital role in making sure that your water is kept free of harmful substances. These plants are able to purify our water through natural as well as chemical processes and will continue to innovate in order to meet new challenges.

This can lead all of us to have a greater appreciation for our local water treatment facilities and all of the work that goes into having clean water.

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