Study On The Rural Drinking Water Safety Guarantee System And Engineering Measures In Arid And Semi-arid Area

Water is the basic element for human survival and development, and drinking watersafety has been the focus of the world people’s attention. In China’s arid and semi-arid regions,however, due to the drought, water shortage, ecological fragility，lag of the water supplymeasures，the problem of drinking water safety has been seriously endanger the health of thepeople, and the harmonious development of the local socio-economic. In order to solve theproblem, and make the drinking water safe in rural areas, the research on the theory,engineering and management measures is an urgent need, and the theory should be systematicand scientific, engineering technology mature and efficient, management measures sound andeffective, This dissertation studies on the rural drinking water safety guarantee system of thearid and semi-arid area, from the aspects of overall planning, water sources and water sourceregions determination, intake measures, treatment process, pipe network optimization andconstruction management, to establish the rural drinking water safety rational guaranteesystem. The main contents include：(1)Based on the study of rural drinking water supply situation and the existing problemsin arid and semi-arid area, China, the connotation of this area’s rural drinking water safetysystem is extended to an integrated system, which contains adequate water quantity, safewater quality, high supply guarantee rate of water sources and facilities, easy to take,affordable prices and so on. The evaluation index system and the evaluation criteria of therural drinking water safety in arid and semi-arid area are analyzed, and the index systemcontains water quality, water quantity, water pressure, convenience, guaranteed rate and waterprice. On the basis of the connotation and requirements of rural drinking water safety in aridand semi-arid area, the rural drinking water safety framework, which covers engineeringtechnology and management maintenance, is built.(2) In the arid and semi-arid area, water sources are scarce and unevenly distributed, andresidential water consumption is obvious different along with the time, according to theprinciple of multi-water sources jointed dispatch, centralized and decentralized water supplymode combination, according to the time and demand, three water supply modes is proposed:zone water supply, dual water supply and timing water supply, and each water supply mode isdiscussed in detail. The calculation method of the water supply scale under different watersource conditions and water demands are also provided.(3) According to a variety of types of drinking water sources in the arid and semi-aridarea, water sources optimal principle and a variety of water quantity, water quality evaluation calculation method are proposed. The determination of water source regions are made fromvarious demonstrate factor: for instance, the factors of quality, river terrain, engineeringgeology and construction condition are for surface water and the factors of hydrological,geological conditions, water ecological environment and construction cost are for groundwater, and soil infiltration, runoff and so on are for rain water.(4) Groundwater as the main source of rural drinking water in the arid and semi-arid area,certain type of intake structures could be selected according to the characteristics of the watersource. When the groundwater buries deeper, with thicker aquifer or many layers of it, deepwell or open well can be used for supplying water. When the groundwater buried shallowerand aquifer is thinner, undertow-interception works can be applied. In the Northwest LoessPlateau region, the radial well and seepage well integrate characteristics of the vertical andhorizontal groundwater intake structures, achieve the nice interception and storage effect. Inaddition, in the areas of water extremely scarce, rainwater cellars can be used to collectingrainwater, which is an effective means of gathering drinking water. A detailed study is carriedon the process principle, characteristics, scope of application, engineering structures, anddesign calculations of the every water intake structure involved in the above.(5) According to the characteristic of rural drinking water projects in the arid andsemi-arid area, water processing system is divided into the raw water treatment and householdwater storage facilities water treatment. Raw water treatment process should be selectedaccording to the water source quality: If the water meets the standard Ι class, directdisinfection can be used; when the water turbidity degree is less than20NTU, slow sandfiltration is suitable; when the turbidity degree varies at20~500NTU, coarse filtration+slowfiltration is appropriate; when the turbidity degree exceeds500NTU, pre-precipitate facility isused before the coarse filtration+slow filtration. For the household water storage facilitieswater treatment, the secondary pollution could be prevented by secondary disinfection andcleaning regularly.(6) Research on the pipe network system security is carried from three aspects: the pipenetwork layout, delivery pipe and distribution system. First, by using remote sensing (RS)technology, combining with field investigations, the lack and lag parts of design data ismodified, in order to get the rational planning of water supply and the precise arrangement ofthe pipeline. Second, for the difficult constructed，gravity type inverted siphon deliverypipeline with long distances, high water pressure in rural area, improved hydraulic calculationequation, methods of pressure bearing and backup safeguard are proposed. Finally, by plottingthe diameter-price correlation curve and combining different pipe head loss formula, economic diameter equations of gravity tree pipe network is established.(7) On the basis of studying on the rural drinking water project management model andorganizational structure, management protection measures of rural drinking water safety inarid and semi-arid areas is proposed. On one hand, the management and protection mode ofthe rural drinking water project is built: be administrated by the water management chiefstation and water management branch station, and supported by the township watermanagement committees and village water user association. On the other hand, thecomprehensive supervision system is established, including construction supervision, projectmanagement, water security management and the water charges.(8) Taking the Dianxia Southward Transfer Rural Drinking Water Project as an example,this has the typical characteristic of northwest rural water supply. After the pre-evaluating tooverall project safe performance, the water distribution network with unsafe water pressure isredesigned, and then the post-evaluation indicates that the rural drinking water project basedon theoretical system of this dissertation is feasible and safe.