A complete water treatment project involves multiple types of pipelines, and suitable materials need to be selected based on different functions and media. The specific selection criteria are as follows:
(1) Welded steel pipes can be used for sewage pipes, sludge pipes, air pipes above the water surface, recycled water pipes, overflow pipes, vent pipes, slag (sand) pipes, and other pipelines for municipal sewage and wastewater with low corrosiveness. For projects with high requirements, welded steel pipes or PP pipes should be used for the water part of the air pipe, and the corrosiveness of wastewater should be fully considered for the underwater part. ABS, UPVC, HDPE or stainless steel pipes should be selected.
(2) The material of the medication tube can be selected from rigid polyvinyl chloride (PV (- U) water supply pipe or PE pipe.
(3) Water supply pipes can use plastic water supply pipes, plastic and metal composite pipes, copper pipes, stainless steel pipes, and steel pipes that have undergone reliable anti-corrosion treatment. If there are no special requirements, PVC-U water supply pipes are commonly used and connected by adhesive bonding. PE pipes, hot melt or flange connections can also be used. The hot water pipe adopts PPR pipe (S2 grade), connected by hot melt method, making PPR pipe installation more convenient. Plastic pipes should not be used for the water supply riser of high-rise buildings. Galvanized steel pipes (threaded for small diameters, welded for DN50mm and above) can be used. Two coats of epoxy coal tar paint should be applied to the buried part, and silver powder should be applied to the indoor part. It is recommended to use rigid polyvinyl chloride (PVC-U) water supply pipes for the chlorination room pipeline. Reusable water pipes can be made of PE pipes and steel pipes.
(4) Outdoor drainage pipes can choose to use concrete pipes or reinforced concrete pipes. The material list should indicate whether it is Class II or III, and the interface should be coated with cement mortar. Plastic drainage pipes can also be used, and buried plastic drainage pipes can use rigid polyvinyl chloride (PVC-U) drainage pipes (diameter below 300mm can be used), HDPE pipes (diameter greater than 160mm can be used), glass fiber reinforced plastic sand pipes or steel pipes (diameter ≥ 300mm). In general, if the diameter of indoor drainage pipes in sewage treatment plants is less than 300mm, it is recommended to use PVC-U drainage pipes with adhesive joints.
(5) Corrosive wastewater drainage pipes must use corrosion-resistant materials for transporting corrosive wastewater, and corresponding anti-corrosion measures must be taken for their interfaces and ancillary structures. Choose PVC-U water supply or drainage pipes based on the degree of corrosiveness, and HDPE pipes for garbage leachate. Organic wastewater with high corrosiveness and wastewater with high alkalinity can be treated with stainless steel pipes, concentrated sulfuric acid can be treated with carbon steel for corrosion prevention, 10% H2SO4 and 30% NaOH can be treated with stainless steel 316L or UPVC, and 20% NaOH can also be treated with PP-R water supply pipes. Acidic wastewater is treated with polytetrafluoroethylene (PTFE) pipes.
(6) High temperature wastewater pipes should use CPVC pipes, ozone and exhaust pipes, pure oxygen pipelines, and valve materials should be made of stainless steel 316L.
(7) Rainwater pipes are made of concrete pipes (diameter 300mm), reinforced concrete pipes (diameter ≥ 700mm, socket flexible interface pipe, Class II pipe, sand and gravel foundation), high-density polyethylene (HDPE) pipes (300mm ≤ diameter ≤ 600mm) or UPVC (drainage pipe diameter<300mm).
(8) The ventilation and deodorization exhaust ducts and pipes are made of fiberglass reinforced plastic (FRP).
Zhaojiadian Village, Jiaoxi Sub District Office, Jiaozhou City, Qingdao City, Shandong Province ,China
