As the first station to provide safe drinking water for us, the water plant needs to remove suspended solids, colloids and dissolved substances in the raw water through a certain water treatment process. It ensure the needs of domestic drinking water and industrial production, so its importance is self-evident.
The water treatment process of water plant: Raw water-mixing-flocculation & sedimentation-filtration-disinfection-clean water reservoir
The mixing process is required to be completed quickly after the chemical is added. The purpose of mixing is to through hydraulic and mechanical agitation, the chemical could quickly and evenly disperse in the water. Currently, the mixing method is generally water pump mixing, tube static mixer mixing, mechanical mixing and drop water mixing, etc. The mixing time is generally 10-60 seconds and the stirring speed gradient is generally 600-1000 seconds. The flow rate of the connecting pipe after mixing and flocculating is 0.8-1.0m/s.
2. Flocculation & Sedimentation
The flocculation process requires good hydraulic conditions and sufficient flocculation time. The forms of flocculation commonly used are mechanical flocculation, folding plate flocculation, grid flocculation and so on. After mixing, the flocculated water flows into the sedimentation tank. Under the function of gravity, the particles in the water sink to the bottom of the tank. There must be sufficient sedimentation time in the sedimentation process to ensure the water in and out evenly, stable water flow in the tank and improve the sedimentation efficiency as much as possible.
Generally, a sand tank loaded with quartz and filter material is used for pre-filtration treatment. The quartz sand filter material layer in the sand tank intercepts part of the suspended material in the water by adhesion. And then use a security filter system for more precise filtration to further remove fine suspended impurities, organic matter, bacteria, viruses in the water. The most widely used filter element installed in the security filters are the HONGTEK filters: HFA Series High Flow Cartridge, MP Series High Flow Cartridge, PF Series High Flow Cartridge and AP Series High Flow Cartridge.
After filtration, the water turbidity is further reduced, and at the same time, the residual bacteria, viruses lose the protection or attachment of the turbidity, which creates good conditions for the disinfection after filtration. Although water can be coagulated, precipitated and filtered to remove most bacteria and viruses, in order to achieve the bacteriological index of drinking water, a disinfection process is essential. It maintains a certain amount of residual chlorine at the end of the city water pipe to control bacteria multiply and prevent pollution.