Many people may have thought about such a problem: the toilet water, bath water, and vegetable washing water used at home are finally goneLet's follow the "footprints" of sewage and see how it is "reborn and reborn".
Sewage is discharged from our home into the sewer pipe, collected through the sewage pipe network and then collected at the sewage treatment plant. Here, the sewage is treated to turn it into clear and usable water.
The first is primary treatment. The first "checkpoint" is called the screen, which is used to remove suspended or floating matter of different sizes from the sewage, such as fibers, hair, fruit peels, vegetables, wood chips, cloth strips, plastic products, etc., to prevent the pump from clogging. The sewage is then pumped through a submersible sewage pump to the aeration grit tank. Here, fine sediment, mud and other solid particles are slowly removed by gravity. Finally, the effluent flows into the primary sedimentation tank, which further reduces the concentration of suspended solids and reduces the load on the subsequent treatment unit. After the three main processes of grid, aeration grit tank and primary sedimentation tank, about 20% of the pollutants in the sewage can be removed.
At this time, the effluent does not meet the discharge standard, and then the secondary treatment is carried out. There is a tall pond called a biological pond, in which a variety of bacteria and microorganisms grow in activated sludge like cotton wool, which are the "workhorses" of removing pollutants from the water. Microorganisms need food to grow, and their food is a contaminant in the water. During consumption, microorganisms thrive and multiply while breaking down pollutants into harmless substances such as water and carbon dioxide. Among these microorganisms, phosphate bacteria and denitrifying bacteria are well-known, which can remove phosphorus and denitrification, and play an important role in preventing eutrophication caused by sewage flowing into rivers, lakes and seas.
At the end of these operations, some microorganisms may follow the water flow to the next treatment process. Therefore, the secondary sedimentation tank became the best place to hold a "farewell party" for them. After the slurry separation, part of the activated sludge is remixed with the sewage and returned to the front bio-pond to continue its hard workThe other part is directly thickened to remove excess water and sent to a special place for treatment. These sludges are good fertilizers when treated. At this point, the secondary treatment process is officially completed, and approximately 80% to 90% of the pollutants in the wastewater are removed.
Finally, there is ** treatment, that is, advanced treatment, including biological filter, decolorization and disinfection, etc. Here, pollutants are further removed, and stubborn harmful germs and pathogens are killed by chlorine, ultraviolet, ozone and other means to ensure the safety of the effluent.
At this point, the sewage is officially transformed into reclaimed water: some of it can be used for road cleaning, toilet flushing, industrial cooling, garden and farmland irrigation, etc.;The other part flows into the city's water systems, such as the Yongding River and Kunming Lake.
Statistics from the Beijing Municipal Water Bureau show that in 2021, about 1.2 billion cubic meters of reclaimed water was used in Beijing, equivalent to the amount of water in 86 West Lakes. Since November 2007, the Old Summer Palace Ruins Park has been using reclaimed water to replenish the river and lake landscape, with an annual water replenishment of nearly 9 million cubic meters. Reclaimed water has become Beijing's "second water source".
Disclaimer of Warranties
This article is based on:Lao Shen reads.
The content published on this number is only for learning and communication, for the purpose of transmitting more information, if there is a ** marking error or infringement of your legitimate rights and interests, please contact us in time with the ownership certificate, we will negotiate the copyright issue or delete the content as soon as possible. The content is the author's personal opinion and does not represent the position of this number and is responsible for its authenticity.