How to clean a quartz sand filter?

Quartz sand filter Is a common water treatment equipment, often used in the following projects
1 Industrial process water filtration —— Such as nozzle, heat exchange station water protection filtration;
2 Industrial circulating water filtration —— Steel, metallurgy, papermaking, heat exchanger, power, petrochemical, food, air conditioning systems and other industries;
3 Raw water treatment filtration —— Surface water, river water, lake water, seawater, etc.;
4 Irrigation filtration —— Farmland, park, municipal and golf course water filtration;
5 Aquaculture, swimming and water park water filtration.
The function of quartz sand filter is to further purify water through contact coagulation process. How to clean the quartz sand filter?
1 Start-up preparation
Check whether the filter body and various valves, pipelines, instruments and various equipment accessories are intact;
Check whether the flocculant dosing tank is sufficient; whether the metering pump is intact;
Check whether the raw water pump, electrical equipment, various on-site instruments and various auxiliary facilities are intact;
Confirm that various discharge, positive washing, backwashing valves are closed;
Close the filter air vent valve after seeing water;
2 Start-up operation
Operation workflow: exhaust →Rinse → Backwash ( II )→ Positive washing → Water production → Backwash ( I )→ Drainage
Note: After a long period of shutdown, the car should start from the backwashing (I) process.
Exhaust, rinse
During the initial commissioning, because there is air inside the equipment, the exhaust step is set. Open the mechanical filter inlet valve and exhaust valve until water comes out of the exhaust valve, close the exhaust valve, and open the positive washing discharge valve for standby.
In the initial operation of the equipment, each filter layer cannot be formed in time, so the filtration effect is poor, so the rinsing step is set. Open the filter inlet valve and positive washing discharge valve until the effluent turbidity ≤2mg/L.
The above two steps will not be carried out in future operation.
Operating cycle
Open the filter inlet valve and outlet valve, and start the raw water pump and metering pump. When the operation reaches the inlet and outlet pressure difference or the set water production, the operation cycle ends. The operation can be revised according to the actual on-site situation.
Backwash
The purpose of backwashing is to loosen the filter layer and flush away the intercepted substances in the filter layer, thus cleaning the filter layer.
The backwash wastewater should not contain normal granular filter media.
Close the inlet valve and outlet valve during backwashing, open the backwash discharge valve and backwash valve, and the backwash flow rate is generally controlled to prevent the filter material from being flushed out, generally about 3 times of the operation.
Backwashing ends when the transparency of the inflow and outflow is similar. At the end of backwashing, the backwashing flow rate is gradually reduced to facilitate the sedimentation of the filter material according to the particle size.
Positive washing
Open Filter Inlet valve, positive washing discharge valve, the positive washing flow rate is the operating flow rate, the time is generally 10～ 20 Minutes, when the effluent is clear and transparent, the positive washing is completed, and the equipment can be put into operation.
Drainage
Open the filter air vent valve and positive washing discharge valve, and drain the accumulated water in the filter to the filter layer 200mm, the time should be determined according to the specific situation.