Do you know how domestic sewage is treated? What is the process of treatment?

Most people think that the water we flush the toilet will be discharged directly into the river, but it is actually sent to the sewage treatment plant through a complicated underground system. The whole sewage treatment process starts from the pumping station in the factory.

First, all the sewage sent is stored in this underground deep well, which is full of mud, garbage and excrement, including a toxic substance in temporary nitrogen with high content, which will not only bring harm to water resources, but also stimulate algae to grow excessively. The treatment plant will use a giant pump to pump sewage into the drainage channel and send it to the wastewater treatment building on the ground. In the process of entering the sewage treatment building, aluminum sulfate or ferric chloride will be sprayed along the way. These two substances are chemical coagulants, which will gradually change the cement forest from liquid to solid, so that the solid forest can be easily removed after entering the filter screen of the treatment plant. Solid wastes exceeding 2.5 cm are removed by the first filter, including correction stones and plastics, and even valuable precious metals. These solid wastes will be squeezed out by a large press, and the excess water will be squeezed out by the press and sent to the landfill by truck.

Second, the filtered waste water will flow into the large pond of the grit chamber. Dust and sand refer to particles in water and cannot be dissolved in water. They will gradually sink to the bottom of the pool, then be sucked out and transported to the landfill. Next, the treatment equipment will spray the polymer solution in the water to remove the organic particles in the water. Its principle is to combine solid particles in water to form so-called concrete, which becomes like snowflakes. They are heavier than water, so they sink to the bottom of the water. This is how the purification pool of sewage treatment plant works.

Thirdly, after about two hours, the concrete in the water will sink to the bottom of the pool to form a layer of sludge, which will be collected by a rake and pumping system and sent to the sludge treatment building. In the treatment building, it is necessary to spray sludge with another polymer to make it solid, so that the compressor can easily squeeze out the water inside, and the solid sludge after squeezing out the water will be sent to a large incinerator for combustion. The gas released by the incinerator can power many machines, and the ashes will be sent to the landfill. When it finally reaches the treatment plant, the sewage full of pollutants will flow into the tunnel of the discharge pipe and be discharged into the nearby river after being purified by the complete treatment procedure.