What Happens at a Sewage Treatment Plant?


All of the wastewater from your house leaves through the drainpipe, which connects to the municipality water line. The wastewater then passes through the drainpipe until it reaches the treatment plant. Most people think that the wastewater is allowed to travel to the sea. However, this is not true at all. In fact, it reaches the treatment plant, where it is treated with different chemicals. This removes all harmful bacteria from the water, making it pure again. The water at treatment plants collects from many different places. Apart from households, the chemical-infested water from different factories and agricultural fields also accumulates at the treatment plant.

Therefore, there are plenty of different ways in which wastewater is treated at a sewage treatment plant. The water generally passes through a series of different treatment stages before being released into the mainstream again. Obviously, the quality of water is thoroughly tested before it is made available for use once more.

Domestic wastewater is categorised in two different groups: black water and grey water. Black water consists of urine and semi-solid body wastes. Grey water is comprised of washing liquids and the water that moves through the shower drain. As you can imagine, most of the treatment processes are focused on black water.

Primary Stage

During the first stage, the primary aim is to separate all the solids from the liquid waste. This is important because different treatment processes are used for purifying liquids and solids. Sedimentation is primarily used to separate the solids from the liquids. There are large sedimentation tanks at treatment plants. The water is stored in these tanks until the liquids with a higher density – such as grease and sludge – fall to the bottom, while lighter liquids like oil fats rise to the top. Once the water is separated, water-borne microorganisms are introduced into the water to dissolve biological elements. A number of chemicals are also introduced into the water, and a series of skimming processes are carried out in order to remove all harmful bacteria and substances from the wastewater.

Tertiary Stage

The main objective at the tertiary stage is to improve the quality of water that has undergone the primary and secondary stages. A number of filtration agents are introduced in order to remove any lingering bacteria and chemicals. For instance, sand and activated charcoal are primarily used to clean the water.

While this does seem pretty straightforward, it is important to note that treating wastewater takes a bit of time. Once the water has been purified, it is kept in separate tanks. The water is then tested for any traces of harmful bacteria. Regular testing is important in order to ensure that the treatment was effective. The whole process is completely automated. A series of different machines and purifying equipment is used in order to ensure that the water is cleaned thoroughly. Engineers are always available on hand in order to attend to any problems that might arise.

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