Experimental Study On The Structure Optimization Of The Layer Of Sediment Desilting Filter Tank Circular Ring

Sediment desilting filter of circular ring is a new device of treating river sediment, it can precipitate most of the coarse sediment and filter suspended load effectively, plus more, it has the advantage of energy conservation and environmental protection. The irrigation methods of northwest region represented by Xinjiang is drip irrigation, as the underground water resources are limited, the irrigation water generally comes from surface water which sediment concentration is large. At present, the treatment method of the source water from the surface water is generally flocculation and precipitation and filtration in water supply ratio, the way of sediment ejection is mechanical dredging, it needs a lot of chemical agent、human and machine in the process of sediment treatment above, and the silt discharged into the river and residue in the clean water may do harm to the biology of fish and human health. Aiming at those problems and based on the characteristics of sediment desilting filter of circular ring, the structure of the filter layer of sediment desilting filter of circular ring was optimization design on, and research was done on, the result showed that:(1)The design applying to micro irrigation:100 mesh screen was placed on the bottom of the filter tank of sediment desilting filter of circular ring(Length2m×Width1m), stone of 5~50mm particle size was placed as landside seepage berm on the screen, experimental research was done under the condition of clean water and muddy water(Turbidity of muddy water is 450NTU). The result showed that, the flow can reach 45L/s under the condition of clean water, filtration cycle is 12 h under the condition of muddy water in the experiment of sediment filtration, the filter layer was clean after 5 times back flush at the end of the filter cycle, consumed time 10 min, water consumption rate is 1.4%, mud content of the landside seepage berm was 0.4%, reaching the requirements of design.(2)One screen of 2mm aperture and another of the sieve mesh number is 100 were placed as protection on the bottom of the filter tank, the filter material layer was placed from the bottom up, sand of 0.25~0.5mm particle size, layer thickness was 0.3m;Sand of 0.5~1.25 mm particle size, layer thickness was 0.3m.The max flow of per unit area of the filter layer reached 10.72L/m2·s under the condition of clean water, at this time the water level differences of upstream and downstream surface is 0.5m;When the flow was 18.75m/h, and the water to be filtered was about 400 NTU, the filter cycle reached 12 h, the turbidity of effluent is below 20 NTU, met the design requirements(the filtered is between 5-20NTU);The filter layer is clean after seven times back wash, consumed time 18 min, the research above shows that this device replaces the process of secondary treatment in water resources of canal head of the river、pretreatment、rough filtration and slow filtering in the continuous water supply engineering, it is an efficient、energy saving and environmental protection device for separating sediment from muddy water.(3)Through a long time of experiments on sandy water filtering of the filter of sediment desilting filter of circular ring, the result showed that, during the experiment, influent turbidity was 400±10NTU, turbidity of the filtrated water is was below 20 NTU, each filtration cycle is able to reach 12 hours; The filter layer was clean after the seventh back wash, average computing time was 18 min, average water consumption rate was 1.8%, the stability of the filter material is good.