Waste Water Treatment Plant - WWTP / WTP

Waste Water Treatment Plant - WWTP / WTP

These plants remove contaminants/sewage waste from households, commercial buildings and sometimes even get an inflow of commercial wastewater too. It can also receive rainwater and debris from sewers.

STPs play a critical role in keeping residents healthy and safe by cleaning wastewater with a bunch of chemical, physical and biological procedures before disposing it into the environment.

How does it work?

The first step in this water treatment plant is that the wastewater drains to the plant with the help of gravity through the main sewer system.

A mechanical stage then begins called the preliminary treatment or pre-treatment. In this stage, the water moves through the gravel chamber to remove any grit. The gravel is then disposed of at the dump. The water then moves to the bar screens which remove large objects. These are course screens. Next, the fine screens remove smaller objects such as undigested foods, or matches, etc.

Similar to the gravel chamber, the grit chamber allows any grit in the wastewater to settle at the bottle. This is then removed from the tank and disposed of at the dump. Next comes the sedimentation stage, also known as the primary treatment. In this stage, the water flows to the primary settling tanks, also known as pre-settling basins. These tanks have hoppers which are situated in the base of the tank where water flows through. This hopper moves around the edges which results in the treated water staying at the edges and the particulates in wastewater that contains the highest sedimentation are settled on the bottom of the tank.

After the primary treatment ends, the secondary treatment begins. This is also known as the biological stage, as it uses natural processes and bacteria that consume the contaminants in the water, such as any biodegradable organic compounds, carbon and phosphorus. This dead bacteria and organic residues then transform into sludge. During this stage, the excess sludge (any excess bacteria in the wastewater) is pumped out and moves to the settling tanks. These settling tanks enable the sludge to settle and then moves to digestion tanks.

In the digestion tanks, the sludge is heated and mixed. Another important thing that happens here is the production of biogas, which the wastewater treatment plants can reuse, in the production of electrical or thermal energy which is another huge benefit to the environment.

When the sludge reaches an optimal level in the digestion tank, the next digestion takes place in the storage tanks. This enables the separation of water from the semi-solid sludge, whereas the remaining sludge undergoes the mechanical process again for dewatering, that is taking out as much water from the sludge as possible. The sludge then left behind after the digestion and dewatering process is complete, is finally disposed of in the dump. Another interesting thing is that this sludge in about a months time, can be reused as an fertilizer for industrial crops, if it complies with all agricultural standards.

The last step in wastewater treatment is inspection. This inspection involves checking the contamination level of the water treated and making sure it complies with the highest standards in order to be released or reused for domestic or industrial purposes.

Applications

Most petroleum refineries or petrochemical as well as chemical industries produce a large amount of wastewater and require on-site wastewater treatment plants. Other industries such as paper and pulp production also give rise to a huge amount of wastewater.

Sewage Treatment Plant - STP

Wastewater is the water that originates from water used in domestic, agricultural, industrial as well as medical or transport activities.