The main factors that affect the operation of sand filter are filter speed, backwash and water flow uniformity.

(1) The filtering speed of sand filter shall not be too slow. Because the filtration speed is too slow, the water treatment capacity per unit filtration area is small. In order to achieve a certain amount of water output, it is necessary to increase the filtration area and investment. However, if the filtration rate is too fast, not only the head loss will be increased, but also the filtration period will be shortened, and the quality of the effluent will be reduced. The filtration rate is generally 10-12m/h.

(2) Backwashing is used to remove the sludge in the filter layer and restore the filtering capacity of the filter material. In order to clean the sludge, there must be a certain backwashing speed and time. This is related to the size and relative density of filter material, expansion rate and water temperature. The backwashing strength of quartz sand for filter material is 15L / (M2 · s). When backwashing, the expansion rate of the filter layer is 25% - 50%, and the backwashing time is 5-6min. Only with good backwashing effect can the sand filter operate well.

(3) The uniformity of water flow, whether in operation or backwashing, requires a uniform distribution of water flow in each section. To make the water flow uniform, the drainage system should be in good condition. Only the uniformity of water flow can make the filtration effect good.

5 replacement procedure of sand carbon

1) . tools needed to replace sand carbon: pipe tongs, sand suction pipes, raw tape.

2) . before replacing the sand carbon, check the filter comprehensively to see if there are any damaged parts of the filter. If there are any, explain to the customer in time and record the operation parameters, especially the water inlet pressure of quartz sand and activated carbon.

3) . for the shutdown of the equipment, first, stop the main pump of the reverse osmosis if there is reverse osmosis, then stop the raw water pump, and then close the water inlet of the raw water pump.

4) . for the disassembly of the equipment, for the larger sand carbon tank such as 2472 tank, the pipe tongs can be used to open the bushing, and for the smaller equipment such as 1354 tank, the pipe tongs can be used to directly open the bushing. Use the sand suction tank to suck out the sand carbon in the tank. The sand carbon is siphoned. Pay attention to exhaust the air in the suction pipe.

5) . when changing the sand carbon, it is generally to change the carbon before changing the sand, because the activated carbon just loaded should be soaked in water to make it fully wet, and the air between the carbon particles and the internal space should be removed so that the carbon particles do not float on the water, which is also to save time. First, put a small amount of water at the bottom of the carbon canister, and then put the activated carbon into it.

6) The filling volume of activated carbon is about 70% of the total volume of carbon canister. So as to leave enough space for backwashing. Fill the carbon tank with water after filling, so that the water can completely soak the activated carbon.

7) Before sand replacement, a small amount of water should also be injected into the sand tank. Quartz sand should be filled in the order of large sand below and small sand above. The filling volume of sand is about 70% of that of the sand tank.

8) . after sand filling, reinstall the equipment. Before washing, make sure whether the valve is opened correctly, i.e. water inlet valve and upper discharge valve, and close the water inlet valve of activated carbon. Then turn on the raw water pump, first wash, and then backwash. And then wash alternately. Know that the water from the waste water valve is clarified to.

9) . make sure that the quartz sand has been cleaned, turn on the raw water pump to clean the activated carbon, wash it before backwashing, and then put it into use after the water is clear and colorless without micro particles. When cleaning the activated carbon, close the water inlet of the softener.