1. Sand Media Filter
In operation, the following cleaning process points of the filtration system must be achieved: the filtered clean water must be used for backwashing; During operation, the backwash flow control valve installed on the blowdown pipe must be checked to make it work properly. Sand media filters generally use high concentrations of chlorine for chlorination during the backwashing process; At the end of irrigation, the water inside the filter should be drained; In order to prevent algae growth, the laminated and mesh type add an appropriate amount of chlorine or acid to the filter, soak the filter cleaner for 24 hours with water, and then backwash until the clean water is discharged and drained for later use. For low-flow rate filters, the most contaminated part of the upper layer of the filter should be regularly removed and supplemented with an equal amount of cleaning media. Depending on the water quality, it is necessary to wash 1~6 times in an irrigation season. Generally, after 1~2 irrigation seasons, the filter medium needs to be supplemented or replaced according to the water quality.
For manual backwash filters, the following methods and steps should be followed.
- Adjust the opening degree of the headmaster valve to obtain sufficient backwash pressure;
- Slowly open the backwash control valve and the backwash flow control valve on the sewage pipe;
- Use a 100 mesh filter or nylon sock cover to undertake the backwash water flow, and check whether the filter material is flushed out, when it is just found that the filter material is flushed out, immediately lock the backwash flow control valve in this position, and it must not be changed thereafter;
- During operation, when the difference between the upstream and downstream pressure gauges of the filter exceeds the preset pressure value of 0.02 MPa, it is necessary to backwash immediately.
Key points for the operation of automatic backwash sand filters.
- First of all, through the test, determine the difference between the head of the inlet and outlet when the filter passes through clean water;
- The difference between the head of the inlet and outlet increases when the filter is working, and this added value should not be > 3.0 m;
- The above two values are added together to obtain the preset differential pressure value of the filter, and the effect of each backwash should be carefully checked at the beginning of the system operation. Therefore, the preset pressure difference value is adjusted appropriately to achieve a satisfactory backwashing effect;
- In order to prevent the water collection device at the bottom of the tank from being blocked by fine filter material, the pressure difference should not be too large, and the frequency of backwashing can be moderately increased;
- Regularly check whether the water discharged from the sewage pipe is clean, if it is found that the water discharged at the end of the backwash still contains impurities that need to be discharged, it means that there are still such impurities in the tank, and the backwash time should be appropriately extended;
- A slight delay must be allowed before the backwash control valve from one tank closes to another is fully opened, during which time the pressure in the tank rises back to sufficient backwash pressure.
2. Irrigation Screen Filters
At present, the field drip irrigation project is more widely used to manually flush the screen filter, which is not easy to master during operation, and generally, when the pressure difference exceeds 0.02 MPa of the set value, it should be flushed immediately. The method is to open the cover, first pull out the filter core for cleaning, and rinse the protective sealing ring at both ends with clean water, or you can use a soft brush to gently brush. However, it can not be brushed with a hard brush, and extra care should be taken in maintenance, storage, transportation, and installation, and there must be no damage, and once it is found damaged, it should be replaced immediately.
3. Irrigation Disc Filters
Whether manual or automatic, the pressed laminate needs to be loosened, which must be able to loosen itself. Due to the influence of organic matter and chemical impurities in the water body, some laminations are often stuck together and are not easy to rinse thoroughly, and great attention must be paid to the use of such filters. Manual cleaning is carried out as follows.
- Close the butterfly valve. If there is a tee or valve dedicated to sand removal when the pump is opened, please open it.
- Open the 3.33 cm (1 inch) ball valve for fertilizer injection and drain the residual pressure from the filter.
- The small ball valve that opens the laminated filter drains the pressure, opens the fixed housing on the filter unit, and removes the housing (placed on the side of the housing).
- Loosen the lamination of the filter element, open the small manual valve for flushing connected between the butterfly valve and the pressure relief valve, and rinse the laminate with high-pressure water in the hose connected to it, without removing the entire filter element. You can also use a container to connect water and place the filter element in it to wash.
- After the filter element is cleaned and screwed tightly, the inner chamber of the filter unit must be rinsed to remove the fine dirt remaining in it.
- Snap the filter unit housings with rubber seals one by one. Be sure to take care not to screw the shell and lid to death. There should be a gap of 0.5 cm before the two.
4. Hydrocyclone Filter
When the flow rate is uneven and the change range is large, measures should be taken to make the flow rate within the design flow range. In addition, the head loss of the filter should be observed at any time, and at < 3.5m, impurities in the water will not be separated. In operation, it is necessary to check the sand collection tank frequently and discharge the sand in time to avoid too much sand accumulation in the sand tank, so that the deposited sediment is taken to the system again. After the end of the irrigation season, the sand collection tank should be thoroughly washed. In order to prevent freezing damage in winter, all valves should be opened and the water should be drained.
