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Quartz sand filter manual


Working Principle

  • Mechanical filter for turbidity removal of raw water. The raw water is sent to the mechanical filter with matching quartz sand at all levels. By using the sewage interception capacity of quartz sand, the larger suspended particles and colloids in the water can be effectively removed, so that the turbidity of the effluent is less than 1mg / L, so as to ensure the normal operation of the follow-up treatment.
  • When flocculant is added into the raw water pipeline, the flocculant will undergo ionic hydrolysis and polymerization in the water. Colloidal particles in the water will strongly adsorb all kinds of products of hydrolysis and aggregation, which will reduce the surface charge and diffusion thickness of particles at the same time. As a result, the mutual repulsion energy between particles will be reduced, and the particles will be close to each other and agglomerate. After the polymer produced by hydrolysis is adsorbed by more than two colloids, The bridging connection is formed between the particles, and the larger floc is formed gradually. When passing through the mechanical filter, it is retained by the sand filter material.
  • The adsorption of mechanical filter is a kind of physical adsorption, which can be roughly divided into loose area (coarse sand) and tight area (fine sand) according to the filling mode of filter material. In the loose area, the main workers produce contact condensation through flow contact, so the area intercepts large particles of suspended matter, and in the tight area, it is mainly inertial collision and adsorption between suspended particles, Therefore, this area is the suspended matter intercepting smaller particles.
  • When the mechanical filter is affected by excessive mechanical impurities, it can be cleaned by backwashing.
  • The sand filter layer in the filter can be loosened by using reverse water inflow and compressed air at the same time, so that the intercepted matter adhering to the quartz sand surface can be stripped and taken away by the backwash water flow, which is conducive to the removal of sediment and suspended matter in the filter layer, and prevents the filter material from hardening, so as to fully restore the interception capacity, so as to achieve the purpose of cleaning.
  • The backwashing cycle is controlled by the parameter setting of inlet and outlet pressure difference. Experience shows that the backwashing cycle is generally one day, which depends on the turbidity of raw water.
  • The mechanical filter adopts stainless steel operation valve group. The start-up, washing, backwashing and shutdown of the filter are all controlled manually.
  • When the pressure difference between the inlet and outlet of the mechanical filter is 0.07MPa, backwashing must be carried out.

Structural Features

The main body of the equipment is a cylindrical steel structure with upper and lower elliptical heads. The filter is made of Q235-A or 304 stainless steel, lined with vulcanized rubber for anti-corrosion. A water distributor is set inside the water inlet, and a water collecting device is set at the lower part. The water collecting device is filled with 1400mm quartz sand.

All kinds of control valves, flow meters and pressure gauges are installed outside the whole equipment. The filler of mechanical filter includes refined quartz sand.

The filter element adopts wedge wire screen which is not easy to block and clean.

Operation Instruction

  • Check whether the filter body and its auxiliary valves, pipelines, instruments and various equipment accessories are in good condition; Check whether the liquid in the flocculant dosing metering tank is sufficient; Whether the metering pump is in good condition; Check whether the raw water pump, electrical equipment, various field instruments and various ancillary facilities are in good condition; Confirm that all kinds of discharge, forward wash and backwash valves have been closed; The exhaust valve of the filter is closed when water is seen.
  • During the initial commissioning, there is air in the equipment, so the exhaust sequence is set. Open the inlet valve and exhaust valve of the mechanical filter, close the exhaust valve and open the washing discharge valve for standby when the exhaust valve is out of water.
  • During the initial operation of the equipment, each filter layer could not be formed in time, so the filtering effect was not good, so the flushing sequence was set. Open the inlet valve of the filter and the washing discharge valve, and run until the effluent turbidity is less than or equal to 2mg / L.
  • Open the inlet valve and outlet valve of the filter, and open the raw water pump and metering pump. When the pressure difference between the inlet and outlet is greater than or equal to 0.07 ~ 0.1MPa or the water volume is set, the operation cycle ends. During operation, it can be revised according to the actual situation on site.
  • Close the inlet valve and outlet valve, open the forward wash discharge valve, inlet valve and backwash inlet valve, and conduct steam water mixed scrubbing at the air inlet intensity of 10 ~ 15L / s.m2 (air pressure of 1 ~ 1.5kg / cm2) and water flow rate of 10 ~ 15m / h for about 10 minutes
  • The purpose of backwashing is to loosen the filter layer and wash away the intercepted materials, so as to clean the filter layer. The length of backwashing time is related to the amount of sewage intercepted by the filter and the backwashing velocity. The backwash drainage should not contain normal particulate filter media. When backwashing, close the inlet valve and outlet valve, open the backwashing discharge valve and backwashing valve. The backwashing time shall be determined by the turbidity of backwashing drainage. Generally, the backwashing time shall be no less than 20 minutes until the turbidity of drainage is less than 3mg / L.
  • Open the inlet valve of the filter and the forward washing discharge valve, and run until the turbidity of the outlet water is less than 1mg / L, and press forward washing until the turbidity of the outlet water is less than 1mg / L, and not less than 30 minutes.
  • Open the filter exhaust valve and washing discharge valve, and drain the accumulated water in the filter to 200 mm above the filter material layer. The time should be determined according to the specific situation.


  • The equipment and accessories have been strictly inspected in our company and delivered after passing the inspection. Therefore, it is unnecessary to disassemble and open the assembled equipment and accessories. However, the delivery list should be carefully checked. Check and check the goods to ensure the smooth installation process. When the equipment is transported or unpacked, it is found that the existing paint and antirust layer are damaged, and necessary repair shall be carried out. During installation, electric welding and gas cutting are not allowed on the surface of the equipment body to ensure that the internal rubber lining is not burned.
  • After the installation, piping and instrument works of the equipment are completed, and the cleaning of the equipment body and piping is completed, the inspection and maintenance shall be carried out according to the following inspection items.
  • After commissioning and entering normal production, the operators should patrol the equipment site regularly every day. Record the results of patrol inspection truthfully and summarize them together with the operation records as the data of regular maintenance.
  • In order to shorten the parking time of regular inspection, the inspection shall be conducted at the same time as other equipment and devices of water station with the permission of the number of inspectors and maintenance workers. If any abnormality is found during the inspection, it must be handled in time and solved.