Design Of Automatic Sampling And Detection System For Underground Water Layer Based On Low Flow And Disturbance

Establishing a monitoring network is an important way to control groundwater pollution,in which sampling is the key link.At present,groundwater sampling mainly adopts multi-layer mixing,large flow and manual sampling,which is inefficient,and mostly carries out off-line laboratory analysis.The detection results cannot truly reflect the pollution of each layer.Therefore,an urgent is needed for an automated sampling and in-situ water quality detection system.In this paper,the groundwater in Zhangjiawan area of Beijing was took as the object,the automatic detection system of groundwater stratified sampling was designed by using low flow and low disturbance stratified sampling technology.The experimental results show that the system realized the layered collection of groundwater and in-situ detection of water quality parameters,and provided samples for heavy metal and organic matter detection instruments,which is of great significance and practical value for the construction of groundwater monitoring network in our country.(1)In view of the problems of multi hole monitoring well covering a large area,high construction cost and the sampler repeatedly crossing the aquifer to disturb the groundwater in the stratified sampling of single hole well,this paper analyzed the existing groundwater stratification mode,designed the packer,realized the effective separation of groundwater,and detected the stratification effect through the water level detection probe.(2)In order to ensure the normal use of the water level detection probe at 100m downhole,a package design was carried out on it.Using threaded connection and double O-ring sealing method,through static analysis and optimization,to ensure the sealed use of the sensor.(3)In order to realize the automatic control of water sample collection,a sampling control system based on STM32 was designed.Multi parameter sensors were used to detect the water quality parameters such as temperature,pressure,conductivity,pH and total dissolved solids.The automatic collection of groundwater and the collection,storage and transmission of water quality data were realized.(4)In order to solve the problems of large disturbance and low representativeness of samples in the process of sampling with large flow submersible pump and manual sampler,the screw pump with small disturbance was selected as the sampling pump,and the frequency converter was used to realize low flow sampling.(5)The Zhangjiawan area was selected for experiment and application.The test results show that the groundwater sampling system designed by this paper has realized the automatic collection of groundwater layers and the in-situ detection of conventional water quality parameters.Through theoretical and experimental analysis,the best operating parameters have been obtained.