Study On The Applicability Of Combined Water Intake Technology Of Collecting And Storing Dams And Bank Filtration To Shallow Water Rivers In Mountainous Villages And Towns

The issue of drinking water safety in villages and towns is directly related to social stability and sustainable development.Implementing water supply safety projects in villages and towns is an urgent requirement for building a new socialist countryside,and the Party,state,and governments at all levels have always attached great importance to it.As of 2021,the population of villages and towns in China has reached 509 million.In order to ensure the healthy water use of residents in rural areas,especially in mountainous areas,it is necessary to strengthen attention to water supply safety issues.The terrain of mountainous villages and towns is complex and the climate is variable,and many places have relatively scarce water resources.As the main water supply source for mountainous villages and towns,shallow rivers such as streams bring great inconvenience to water supply plants due to their low flow rate in dry seasons and high turbidity and pollution in rainy and flood seasons.The construction of barrages and water collection tanks not only has high cost and large engineering volume,but also carries a large amount of sediment and floating debris during rainy and flood seasons,which can easily cause problems such as blockage and sedimentation,affecting the normal use of the water intake head of the water plant,causing inconvenience to the operation and management of the water plant,and affecting the normal water use of residents.Therefore,based on the investigation of 123 surface water sources in villages and towns,combined with the water supply characteristics of mountainous villages and towns,this article proposes a combination of collection and storage dams and bank filtration water intake technology as a pre-treatment measure for shallow rivers such as streams.Turbidity is intercepted and pollutants are removed through riverbank filtration,and infiltration into streams is intercepted and collected through collection and storage dams to meet the requirements of water plants for inlet water quality and quantity,And the feasibility of this technology was verified through laboratory experiments and simulation with HYDRAS-3D software,and a demonstration project was ultimately built.The main results are as follows:(1)Water sources in mountainous villages and towns are seriously polluted and have poor water quality.Among the 123 water sources surveyed,the excess turbidity rate is 61%,the excess total phosphorus rate is 28%,the excess nitrogen content rate is41%,and the excess CODMn rate is 44%.At the same time,shallow rivers,as the main water source for water supply in mountainous villages and towns,have brought great challenges to the water supply in villages and towns due to their poor water quality in rainy and flood seasons and small water volume in dry seasons,affecting the normal operation of water plants and seriously endangering the daily water safety of rural residents.Therefore,pretreatment of such water sources has direct practical significance for ensuring the water safety of rural residents.(2)The three sets of shore filtration systems(gravel layer,sand layer,and mixed layer)built in the laboratory have good removal effects on various pollutants in the water,such as turbidity,ammonia nitrogen,CODMn,antibiotics,and pesticides.Overall,the removal of pollutants by filter columns is mainly concentrated in the range of 0-40 cm above the filter layer,with the highest removal efficiency of pollutants,accounting for over 80% of the total removal rate.However,within the range of 40-75 cm,the removal rate of pollutants becomes increasingly low.At the same time,by introducing air ducts into the shore filtration system and replacing about 40 cm of filter material,the decontamination ability and impact load resistance of the shore filtration system can be greatly improved.(3)The simulation results of HYDRUS-3D software show that the combined water intake technology of collecting and storage dams and bank filtration is of great help to improve the water production of infiltration wells and the storage capacity of the system.At a water level of 20 cm,the construction of a collection and storage dam has increased the water production of infiltration wells in the gravel,sand,and mixed layer bank filtration systems by 83.6%,82.7%,and 78.5%,respectively,and the total water storage capacity of the system has increased by 48.2%,47.6%,and 45.6%;At a water level of 50 cm,the construction of the collection and storage dam has increased the water production of infiltration wells in the gravel layer,sand layer,and mixed layer bank filtration system by 82.4%,84.6%,and 80.6%,respectively,and the total water storage capacity of the system has increased by 51.3%,52.6%,and 46.5%;At a water level of 80 cm,the construction of a collection and storage dam has increased the water production of infiltration wells in the gravel,sand,and mixed layer bank filtration systems by 79.8%,82.6%,and 80.6%,respectively,and the total water storage capacity of the system has increased by 58.1%,53.6%,and 47.2%.(4)According to the continuous monitoring results of the water quality and quantity of a seepage well in a water source area in Dajing Town,Shangluo City,the application of the combined water intake technology of the bank filtration of the collection and storage dam has played a significant role in improving the water quality and stabilizing the water quantity of the water source in the area.The removal rate of conventional pollutants such as turbidity,ammonia nitrogen,and CODMn in the source water is over 75%,and the removal rate of trace organic substances such as hormones and pharmaceuticals is over 50%,and the water supply in the dry season reaches 3000m3/d.It ensures the normal operation of the water plant and effectively reduces the operating load of the water plant.