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31-08-2021

Clear view in wastewater treatment plants

Written by Karst Beens

In a nutshell: Wastewater treatment plants clean a community’s wastewater so that it can be recirculated.

But, if you take a closer look, the purification is a longer process in which the water passes through different basins. This week we want to explain the process of wastewater treatment plants and especially why the use of an underwater drone are more efficient here than divers.

How does a wastewater treatment plant work?

The wastewater in a wastewater treatment plant passes through 7 different basins before it is completely cleaned.

  1. Wastewater pumping station: In this step, sewers convey the wastewater to pumping stations. The pumping station then transports the wastewater under pressure into the treatment plant.
  2. Screening plant: The water is flushed over the rake. This removes the initial and coarse impurities from the water. This includes, for example, food residues, hygiene articles and the like. The sorted out waste, is then dried out and taken to the nearest landfill or waste incinerator.
  3. Sand trap: In the sand trap, smaller particles are filtered out of the wastewater, such as sand, stones, etc.. The water is transported over long channels at a speed of 30 cm/second. As a result, the smaller particles settle to the bottom of the grit trap. Thereupon, these are also dried again and then disposed of.
  4. Primary clarifier: In the primary clarifier, lighter sludge particles are filtered out of the water. For this purpose, the water velocity is reduced to 1.5 cm/second. Sludge particles then settle to the bottom of the water and are led through sludge funnels to the sludge treatment where the sludge is later reused. In this phase not only the sludge is filtered out of the water but also other particles such as grease. These particles do not settle on the bottom but on the surface of the water. This, however, allows them to be easily removed.
  5. Aeration tank: After all visible particles have been filtered out of the water, the invisible particles are removed in the aeration tank. For this purpose, microorganisms are added to the water, which then form an activated sludge. The aeration tank is divided into two parts, the first of which is kept low in oxygen to remove phosphorus. In the second part, a lot of oxygen is then added to the aeration tank, allowing the purifying bacteria to multiply.
  6. Secondary sedimentation tank: In this step, the sludge added to the aeration tank is removed. Here, the water stands in a basin so that the sludge can slowly settle again. Half of the sludge is transported back to the aeration tank and the other half is added to the sludge treatment. After this step, the water is cleaned again.
  7. Sludge treatment: In the last section of the treatment plant, the sludge is dried and then further processed or disposed of.

Our work in wastewater treatment plants

Sewage treatment plants also need to be inspected. Each tank can show damage and a regular inspection can prevent major repairs. However, the problem is that most sewage treatment plants are running and are not shut down. This prevents divers from entering the tanks. At the moment, however, this is the method used. The basins are stopped so that divers can perform the inspection. This results in losses for the treatment plant, which means that inspections are only carried out when there is suspicion of damage and not preventively.

But it is the preventive inspection that is important. During an inspection with our drones, the sewage treatment plant can continue to run and does not have to be interrupted. The cloudy visibility caused by the sludge is not a problem because of our sonar. And our drone can also handle currents. This makes it easier to carry out regular inspections. And divers no longer have to climb into sewage!

 

 


Do you have any questions about our work in wastewater treatment plants? Feel free to contact us here.

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