The first thing that domestic sewage passes through is the grate, which generally has two thick and thin grates. The coarse grille has a gap of 10-30 mm, and the fine grille has a gap of about 3 mm. Floating and suspended matter in sewage is intercepted when passing through here, and is transported to the slag dumping point by a screw conveyor or belt conveyor, and is then transported to a landfill for landfill. In order to reduce the complexity of the subsequent system and save energy, the sewage filtered by the coarse and fine grilles (sometimes after the coarse grille and before the fine grille) is generally lifted to the highest point of the entire sewage plant through the pumping station, and then flows through the subsequent flows by gravity. processing facilities. If the city you are in has industrial wastewater mixed into the municipal pipe network (it is generally more or less mixed in China), the domestic sewage treatment plant will need a hydrolysis acidification tank for further decomposition treatment. This type of pool mainly creates an anaerobic environment, allowing anaerobic bacteria to break the macromolecular chains in the sewage and eat some of them, and at the same time, precipitate part of the sediment and other inorganic matter in the sewage. Generally, gases such as hydrogen sulfide and methane are produced here, and the smell is very bad.