Auto Backwash Shallow Sand Filter for Power Plant

1.Shallow sand filter product introduction:
The shallow sand filter uses quartz sand filter material as the media filter element, and the water is filtered from top to bottom. The device is generally composed of multiple standard high-speed sand tank units with unique water distributors and water collectors inside. , With a unique two-way automatic flushing valve, it can realize the back flushing of multiple standard high-speed sand tanks one by one in the normal system operation, and fully automatic program control. 

2. The working principle of shallow sand filter
a) Positive washing filter state
When the system is in the filtering state, the unfiltered water is evenly distributed through the unique water distributor, and the water passes through the filler layer in the filter in a laminar flow state. When water flows through the packing layer, impurities are trapped in the packing layer. There are multiple evenly distributed water collectors at the bottom of the filter to collect and draw the filtered water evenly. Advection filtering can make the filter filter at a high flow rate and still achieve a better filtering effect.
b) Backwash state
As the impurities accumulate in the packing layer, the internal pressure head loss will continue to increase. When the pressure head loss of the inlet and outlet water reaches the set value, the system will automatically activate the constant pressure device to switch to the backwash state. When the backwash is completed, the hydraulic valve changes the water supply direction to realize the backwash one by one, which is more convenient Clean the accumulated impurities.
When the system is in the backwashing state, the filtration continues. The standard unit sand tank to be backwashed is not filtered, and the other standard unit sand tanks in the system are still filtering. Part of the filtered clean water is used to backwash the standard unit sand tank, and the rest is still sent to the user. The backwash sewage is discharged through the backwash drain of the hydraulic valve. In the high-speed sand tank automatic high-efficiency filtration system, the special water trap design can make the fillers between the fillers scrub each other, maximize the backwash efficiency, reduce the required backwash water (clean water), and at the same time backwash There is no material running out. The backwashing of a standard unit sand tank is 2 minutes. After the backwash is completed, the pressure head loss in the standard unit sand tank is reduced to a reasonable range, the constant pressure device gives a restoration signal, the hydraulic valve returns to the filtering state, and the next standard unit sand tank It is ready to enter the backwash state.

3.Shallow sand filter design parameters
a) Working temperature: 3~70oC;
b) Operating flow rate: 35~50m/h;
c) Working pressure: 0.35~0.5MPa;
d) Water backwash intensity: 10~14L/m2.S
e) Backwash duration: 2~3min;
f) Filling height of filter layer: 400mm;
g )Backwash form: water washing;
h) Operation mode: automatic;
i )Material selection: carbon steel, 304, 316, 316L stainless steel;
J)Filtration accuracy: Influent turbidity≤40mg/L, effluent turbidity≤5mg/L;

4. Product features of shallow sand filter
a) Small size, easy to install, save space; compact structure, save space; the product has good anti-corrosion performance and can be installed indoors and outdoors.
b) The equipment has good anti-corrosion performance and long service life.
c) Large amount of filtered water, good filtering effect; fast filtering flow rate and high filtering precision.
d) Automatic backwashing: Backwashing is automatically identified and controlled by the intelligent control system without manual intervention.
e) Uninterrupted water supply; when the equipment is backwashed, the filtering process is carried out at the same time, and the system supplies water as usual.
f) Adopt unique cloth and water collection device. Due to the unique water distribution system and evenly distributed water traps of the filtration system, the water flow is laminar during the whole filtration process, the plane of the filter sand bed is always flat during the filtration process, and the effluent quality is stable.
g) Use refined quartz sand or garnet as the filter medium. Choose according to the water quality, the smallest particle size of the filter material can be a homogeneous filter material of 0.16mm.
h)Long-term operation costs are low, saving electricity, water, and maintenance costs.


5. Applicable scope of shallow sand filter
a. The filtration of industrial water has certain system requirements for water quality. Such as: oxygen lance water in steel mills, boiler, heat exchanger water supply filtration, etc., which can filter out impurities in the water and avoid blockage of several nozzles in the pipeline.
b. Filtration system for industrial circulating water.
c. Raw water treatment can filter surface river water, lake water, sea water, reservoir water, well water and urban tap water as the water source of urban subdivision quality water supply, etc., to remove sand, suspended matter, algae, organic matter, etc. in the water.
d. Agricultural irrigation, especially suitable for water sources with high flow and good impurity content, such as irrigation of farmland water conservancy, irrigation of lawns in parks and golf courses, etc.
e. Food processing industrial water, paper industry, power plant industrial circulating water treatment, etc., industrial and medical pure water pretreatment. Industrial production water recycling, industrial wastewater treatment.
f. Industries such as aquaculture, swimming and water parks.
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