Wastewater treatment plant
What does the Wastewater Treatment Plant (WWTP) mean?
Wastewater treatment is the process of converting wastewater – water that is no longer needed or no longer fit for use – into water that can be returned to the environment or reused in some way.
How does the Wastewater Treatment Plant (WWTP) work?
Access to drinking tap water in our households is not unusual. We shower and the water leaves. We use the toilet and all human waste is discharged through the pipeline. We wash the dishes and the water disappears in the sink of the kitchen sink along with the soap. Have you ever considered where that water ends up and what happens to the water used afterwards? Mostly, we believe that is not our concern. At least until we start thinking about wastewater treatment. If you are interested in WWTP, this is the right place for you.
What is wastewater?
That is water that we use in domestic, industrial, agricultural and medical or transport industries. That water becomes wastewater after changing the quality, composition and/or temperature.
Types of wastewater
Wastewater can be divided into two main groups: Sewage wastewater is all domestic wastewater (e.g. it comes from a toilet, shower or sink). Industrial wastewater originates from production, industrial and commercial activities and has a different chemical composition than sewage. In a broader sense, we can distinguish between municipal wastewater from different municipalities. It has a different ratio of sewage, industrial wastewater and rainwater flowing through the sewer network.
How does the municipal wastewater treatment process work?
1. First, the wastewater is gravitationally discharged into the sewer through the main sewer system the size of a smaller car. I that way, items you could hardly imagine reach the purgatory, from car tires, tree branches to wallets thrown by thieves to get rid of the evidence.
2. Water flows through the gravel chamber to deposit sand from the water. After that, the gravel is deposited in the landfill. The water further reaches the sieve bulkheads which are used to remove larger objects from the wastewater. First, come the coarse strainer and then the fine strainer that removes smaller objects such as matches, cigarettes or non-digested foods.
3. After removing large objects, sand is removed from the wastewater. Similar to the gravel chamber, the sandblast allows sand settling. Then, sand is removed from the reservoir and deposited in a landfill. Neither gravel nor sand can be reused because of the high contamination.
4. The next phase of sedimentation is called primary treatment, during which wastewater flows into so-called “pre-deposition basins”. Water is directed toward the bottom of the tank. The treated water goes to the edges, and particles of higher sedimentation velocity than the flow rate settle at the bottom of the reservoir. This is where the primary treatment ends and the secondary treatment of the wastewater begins. After primary treatment, the level of wastewater pollution drops to 60%.
5. The secondary treatment, also called the biological phase, is based on natural processes. For WWTP we use bacteria that consume pollutants, especially biodegradable organic compounds, carbon and phosphorus. The dead bacteria and organic residues are then turned into sludge.
6. During the biological phase, excess sludge (excess bacteria) is pumped and transferred in front of the precipitator. Here the sludge is deposited and transported to the digestion tanks for further processing.
7. In the digestion tanks, the sludge which is pumped from the settling tanks is heated and stirred. Subsequently, sludge biogas is produced during the digestion process. It can be reused by WWTP, for example, for electricity and heat production.
8. When the sludge has reached its optimum level, the second phase takes place in the sedimentation tank. Here, the water is separated from the semi-solid sludge and transported back for further treatment, while the residual semi-solid substance is subjected to mechanical removal of water.
9. The sludge, which is drained to an optimum level, is finally disposed of in the landfill. The precipitate is adequately dried and matured in about a month. If it complies with agricultural standards, it can be reused to fertilize industrial crops.
10. The final step of the wastewater treatment is a detailed analysis of the treated water. The purpose of this inspection is to analyze the level of pollution and to ensure that the treated water complies with the highest standards. Wastewater treatment is certainly a difficult process with a noble aim that requires the work of skilled and experienced professionals.