Water extraction unit 1 water extraction device The water extraction device consists of water pump, pipeline, power supply flow rate regulating device, pressure and flow monitoring equipment, regulating valve, protection pipe and corresponding detection, control and driving electrical circuit. The system shall adopt double pipe and double pump design, one for use and one for standby. Water intake protection, with warning signs. The use of national standard cable, valve using imported products, service life shall not be less than 300000 times 2 water distribution device (1) the water distribution device meets the requirements of the analytical instrument for sample water flow and pressure. (2) the main pipeline of the water distribution device is in series structure, and the main road non blocking filter device is adopted, which is open and expandable. (3) in order to facilitate the maintenance of the system, the water intake pipeline of all instruments is equipped with bypass system. (4) the pressure or flow monitoring device is set in the water distribution pipeline to monitor the operation status of the water collection and distribution unit in real time, with remote control and alarm functions. (5) the pipe has good mechanical strength and chemical stability, long service life, easy installation and maintenance, and will not affect the water quality. (6) there is a manual water intake in the indoor part, which is convenient for water collection in water sample comparison experiment. (7) pipe emptying design is used to prevent algae from breeding in the pipe. (8) the water distribution unit is equipped with pretreatment devices according to different monitoring items. Overall design of water extraction The sampling head should float 0.5-1.0 m below the water surface and have enough distance from the bottom of the water body (dry season > 1 m) to ensure that it is not affected by the sediment at the bottom of the water body. The water extraction system shall be designed with double pumps and double pipelines, which can backup each other and facilitate maintenance. The submersible pump, self-priming pump or submersible sewage pump with good quality shall be selected to effectively prevent blockage, and the flow rate of the pump shall be more than 3t / h; When the outdoor water extraction pipeline exceeds 100 meters, the cable of the water extraction pump should be twice the diameter of the pump line to avoid pressure drop. The water extraction system shall ensure normal water extraction under the condition of continuous flow of the river (there is no water in the upstream and downstream 50m of the water extraction point). According to the change of point position in wet and dry seasons, the water extraction position can be adjusted dynamically. The trestle type water extraction method must be firm and stable, and can resist the impact of flood without being damaged. The water collection device shall be equipped with a cleaning and back blowing system to prevent the formation of algae and avoid affecting the water quality. The water intake should be provided with anti blocking measures. Water intake status can be displayed by flow or pressure and alarm can be given. The pipeline and circuit of water extraction system shall be installed separately. The material of water extraction pipeline shall not affect the water quality. Necessary waterproof, anti pressure and anti freezing protection measures shall be taken outside the pipeline. The electric wire shall be installed with casing. The depth of water extraction pipeline and circuit shall not be less than 80cm. Steel casing must be installed when crossing the road. All pipes in the substation building are made of stainless steel or PVC pipes polished inside and outside. The pipes shall be cleaned before installation. Reasonable flow path design shall be provided to facilitate disassembly and cleaning, and sufficient movable joints shall be provided.