Experimental Study of Air Pump Backwash with Jet Pump

Filter is the most commonly used equipment in water treatment projects. Filter rinse was good or bad, the filter effect of the filter and the economy have a significant impact. Air-water backwash filter than the backwash water alone is good, but the need to set large-capacity air compressors or blowers, due to the high cost of equipment, complex operation, and work vibration, noise, slow promotion. Jet pump filter air and water backwash, you can greatly reduce equipment and operating costs, simplify operations, reduce noise, is conducive to the promotion. The technology has been patented. This article focuses on the results of semi-productive pilot studies. First, the semi-productive test device Jet pump air filter backwash gas and water semi-productive test is carried out on the basis of small indoor tests. Test filter located in Chongqing Municipality hit dam water plant. There are two experimental filter, filter area is lm2, square. A filter with long-handled filter for water distribution system. Figure l (1). The filter head is installed on the diaphragm at the lower part of the filter. The filter heads are arranged in checkerboard with a pitch of 0.14m. Under the partition with a water chamber height of 0.45m. The separator is provided with a thickness of 0.05m of coarse sand (particle size 2 ~ 4mm), on which is 0.3m thick quartz sand filter (particle size 0.5 ~ 1.0mm) and 0.4m thick anthracite filter layer ~ 1.7mm). Drains, the roof from the sand 0.68m. Drainage top with 40 mesh nylon sand control, to prevent air and water backwash filter loss. The total height of the filter is 3.5m. The jet pump is mounted vertically on the filter backwash hose. Jet pump factory water as the pressure water source. Filter backwash, the pressure water jet nozzle jet, the air inhalation, the formation of gas-water mixture, into the lower part of the water distribution chamber filter; gas-water separation, the long-handled filter evenly distributed in the filter plane On the bottom of the filter layer of gas and water at the same time backwash; backwash gas and water, then separate water backwash to exclude the filter layer of bubbles, and the double layer filter layered. After the backwashing wastewater, collected by the upper drain and discharged from the pool. Jet pump Another test filter with perforated pipe for water distribution and gas distribution system, as shown in Figure 1 (2). Perforated water distribution pipes are arranged at the bottom of the pool and are provided with a pebble supporting layer (particle size: 32-16mm, 16-8mm, 8-4mm, 4-2mm. The thickness of each layer is 0.15m, 0.10m, 0.10m and 0.13m ). Perforated gas pipe located in the particle size of 4 ~ 2mm support layer. Support layer double filter layer, particle size and thickness with the former. Drainage from the sand roof is 0.45m. The total height of the filter and other dimensions with the former. The filter and the aforementioned filter share a jet pump. And after the jet pump set up a gas-water separation tank, the water and gas were separated into the perforated pipe water distribution and gas distribution system, bottom-up gas-water filter at the same time backwash. With perforated pipe for water distribution and gas distribution, not only for the new filter, and is particularly suitable for ordinary fast filter transformation. Second, the test results and analysis The test from July 1987 to the end of December, which lasted more than five months, experienced the Jialing River flood period and the flat water period. Sedimentation into the filter water turbidity minimum 3 degrees, up to 25 degrees, an average of 13 degrees; water temperature is 17.5 ~ 26.5 ° C. The test results are described as follows: 2.1 Air and water backwash the best process parameters in order to determine the semi-productive test process parameters, the first 10 columns with two orthogonal test. Filter column diameter of 150mm, length 4m, the lower part of the installation of long-handled filter as water distribution system, the upper part of the filter diameter of 0.5 ~ 1.2mm quartz sand filter, thickness 0.4m, and 0.8 ~ 1.8mm of anthracite filter Material, thickness 0.3m. The test is also being carried out at a dam dam factory, with the same test conditions as the semi-production test. The filter column works with constant velocity filtration, the filtration rate is controlled at 13 ~ 16m / h. When the filter head loss reached 1.7m, backwashing. Backwash water from the factory pressure water supply, backwash air supply from the air compressor. First with air and water backwash several minutes at the same time, and then separate water backwash 2min. The first batch of orthogonal test selected gas-water simultaneous backwash gas-water ratio, the total strength of backwash gas and water and air backwash time, and water backwash strength of four factors were investigated to filter period as an indicator. Choose 3 levels for each factor. The test results are shown in Figure 2. According to the results of orthogonal test and Fig. 2, the main factors influencing the filtration cycle are single water backwash intensity, followed by gas-water ratio and gas-water simultaneous backwashing time, while the total strength of backwash gas- Less affected. This is because when gas and water are backwashed at the same time, anthracite and quartz sand are almost completely mixed. Increasing the intensity of the single water backwashing can make the coal sand well layered and increase the filtration period. The second batch of orthogonal test, air-water ratio of 2: 1 fixed, select the total strength of air and water backwash and backwash time, single water backwash strength and backwash time to examine four factors, each factor choice 3 A level. The test results are shown in Figure 2. From the analysis, it can be seen that the main factor affecting the filtration cycle is still the single water backwash intensity; the other factors are the single water backwash time, air and water backwash time and the total backwash strength. The first and the second batch of jet pump structure test shows that process parameters should be selected air-water ratio of 1.5: l ~ 2: 1, air and water backwash total strength of about 12L / (s.m2), gas and water at the same time Backwash time is 5 ~ 7min, water backwash intensity of 15 L / (s.m2) or so, separate water backwash time to 2min better. 2.2 semi-productive filter operating mode and operating conditions of the test filter filter constant head deceleration by way of work. Pre-filter water level remained above the surface of the sand 1.7m or so. Initial filtration rate control at 14 ~ 17m / h. Filter backwash once every 2d, filtration cycle average of 47h. At the end of the cycle, the final filtration rate is only 3-4 m / h less than the initial filtration rate. The average filtration rate of the filter, perforated pipe water distribution filter for the 13.4m / h, the filter with water distribution filter 14.5m / h. As the pressure of the factory water changes frequently, the water pressure before the jet pump is different during each backwashing of the filter, and generally varies between 2.2 and 3.5 atmospheres. The backwashing strength of water is 4.8 ~ 5.7L / (s.m2) with an average of 5.3L / (s.m2) when the gas and water are backwashed at the same time. The backwashing intensity of the gas is 4 ~ 10.6L / (s.m2) ), With an average of 7.2 L / (s.m2); gas-water ratio of 0.83: 1 to 2: 1 with an average of 1.36: 1; total backwash gas-water strength of 8.8-16.3 L / (s.m2) (S.m2) was 12.6 L / (s.m2); the time of simultaneous backwashing of gas and water was 5 min; the backwash intensity of single water was 12-17 L / (s.m2) with an average of 15 L / (s.m2) Rinse time is 2min. Backwash water consumption rate of perforated pipe water distribution filter is 0.6%, the filter with water distribution filter is 0.59%. Filter backwash, the jet pump is working properly, gas-water separation tank separation effect is good; either long-handled filter or perforated pipe, with water distribution are more uniform; separate water backwashing, coal sand stratification layer is good, Sand surface smooth. 2.3 Test filter drainage turbidity, sewage and muddy filter layer filter muddy water drainage, drainage and filter mud content from different aspects of the filter to reflect the flushing effect. Tests show that the beginning of filter air-water backwash, the turbidity increased drastically, 0.5min before and after the maximum occurs, the turbidity up to 8000 ~ 10000 degrees, then quickly reduce turbidity turbidity at the end of the backwash Can be reduced to 30 to 120 degrees. The removal rate of contaminants can reach 80-88% at the end of gas-water simultaneous backwashing, and can be up to 97.5-99.6% through backwashing with separate water for 2min. Table 1 shows the results of measuring the clay content of the three filter layers during the test period, as can be seen from the table