Environmental Dredging Technology Based On Pollutants Release Rule From Sediment

At present, the river sediment pollution management is faced with severe situation,especially in the Yangtze river three gorges channel backwater reach sediment siltingsituation is very serious, be badly in need of a reasonable and practical environmentalprotection dredging project. To this end, on the Yangtze river waterway dredgingprocess, for grab and Cutter-suction type dredging equipment have poor environmentalbenefit problems, paper research from the dredging equipment structure, operationparameters and environmental transformation, to determine the minimal impact on therelease of pollutants in sediment dredging, and environmental protection improvementdredging methods and dredging equipment, in order to find a suitable for navigationstreamwise alluvial sediment of the Yangtze river three gorges environmental protectiondredging scheme.Paper system elaborated the working principle and characteristics of grab andCutter-suction type dredging equipment, in view of the technical features and theenvironmental protection improvement requirements of the bucket volume8m3grabdredging equipment and productivity of500m3/h Cutter-suction dredging equipment,designed the model structure of environmental protection grab and cutter-suctiondredging equipment, and determined the dynamic test parameters; Through the grab andcutter-suction dredging equipment simulation test, systematic studied the key operatingparameters of environmental protection dredging equipment (grab opening, graspingmud frequency and floating bucket angle and the reamer traverse speed and rotatingspeed), On the basis of research, environmental protection improved the dredgingequipment. The main conclusions are summarized as follows:1) Grab opening, grasping mud frequency and floating bucket angle all have a certaindegree of influence to the release of pollutants in sediment. When the grab opening is180°, accumulation release value of ammonia nitrogen, total nitrogen and organicmatter in sediment is minimum, the maximum cumulative release amount is0.89g/m3,1.88g/m3and67g/m3, followed by190°and150°. When the grasping mud frequencyis40times/h, accumulation release value of ammonia nitrogen, total nitrogen andorganic matter is minimum, the maximum cumulative release amount is0.81g/m3,1.58g/m3and59g/m3, followed by50times/h and60times/h.When the floating bucket angle is0°，accumulation release value of ammonia nitrogen, total nitrogen andorganic matter in sediment is minimum, the maximum cumulative release amount is0.72g/m3,1.33g/m3and52g/m3, followed by10°and20°. At the same time, underdifferent influencing factors, nutrient nitrogen (ammonia nitrogen and total nitrogen)release rate within0.5h after dredging is obvious different. After0.5h, the nutrientnitrogen release rate difference is not obvious, and over time,the decreasing trend ofnutrient nitrogen release rate is more and more slowly and stabilized after3h and closeto zero. As a result, for the purpose of environmental protection, the suitable grabopening, grasping mud frequency and floating bucket angle is180°,40/h and0°in thegrab dredging project.2) With the mud blocking curtain wall, the ammonia nitrogen, total nitrogen andorganic matter concentration increment is53%,48%and52%less than that without themud blocking curtain wall. Show that, in the grab dredging project, the mud blockingcurtain wall is helpful in reducing the pollutants release value, but can not completelyavoid the pollutants concentration increasing in the overlying water.3) Cutter transverse speed and rotating speed all have certain effects on the dredgedmud concentration, and the cutter transverse speed have bigger influence on theconcentration of dredged mud. Analysis shows that, in order to improve the efficiencyof dredging, cutter rotating speed and traverse speed of cutter dredging equipment are40r/min and0.2m/min.4) Using spiral cutter dredging, ammonia nitrogen, total nitrogen and organic matterconcentration increment in the overlying water6%,14%and15%less than that usingordinary cutter dredging after dredging. Using ordinary cutter equipped with the housingdredging, ammonia nitrogen, total nitrogen and organic matter concentration incrementin the overlying water11%,17%and28%less than that ordinary cutter without housingdredging after dredging. Using spiral cutter equipped with the housing dredging,ammonia nitrogen, total nitrogen and organic matter concentration increment in theoverlying water9%,13%and23%less than that spiral cutter without housing dredgingafter dredging. Using spiral cutter equipped with the housing dredging, ammonianitrogen, total nitrogen and organic matter concentration increment in the overlyingwater14%,24%and35%less than that ordinary cutter without housing dredging afterdredging. At the same time,dredging with spiral reamer and normal reamer with housing,the nitrogen release rate within1h after dredging is less than that dredging withnormal reamer and reamer without housing.After1h, under different reamer type, thenutrient nitrogen release rate difference is not obvious, and over time,the decreasingtrend of nutrient nitrogen release rate is more and more slowly and stabilized after5hand close to zero.Show that equipping housing and using spiral reamer dredging areconducive to reducing the pollutants release value in sediment dredging, and the formeris more significant effect than the later. Visible, the spiral reamer equipped housing isthe best environmental protection scheme.This study provides a theoretical basis and technical support for the sedimentdredging construction scheme of the Yangtze river three gorges channel backwaterregion, the research results have important theoretical significance and practical value.