Preliminary Experiment On Fracture-karst Aquifer Recharging With Roofwater

With the rapid development of economic and social, the demand for water isincreasing day by day; Surface water and groundwater pollution have been a seriousproblem. Groundwater is used as the supply water source in many northern cities, insome northern cities, environmental geological problems such as groundwaterrecession, land subsidence, groundwater degradagion and seawater intrusion are evencaused by over-exploited of groundwater geological. As the accelerating urbanizationand increasing impervious area, a lot of rain erosion caused serious waste of waterresources, and the rain can’t infiltration caused by a lot of runoff cannot throughdrainage system to quick eduction, even caused flood, this is do harmful to thepeople’s live and the life.Using urban rainwater recharge groundwater can not only add groundwaterresources and enhance water level, but also through the shunt part to reduce urbanrainwater drainage pipe pressure and investment and operation cost, reduce heavy rainflood disaster occurs. The urban roofwater is light pollution water and has muchvolume, if the stormwater runoff injects directly underground, they would pollute theunderground water sources. The prophase roofwater has higher pollutantconcentration, and the later rain’s pollutant concentration is lower and stabler. Thehigh concentration of pollutants will rain through the early rain abandon flow devicestap, after flow by sediment basins and the term of processing, through the casing wellinjecting to fracture-karst aquifer to supply groundwater. The effects available can beanalysed through the injection wells and downstream of the observation wellsmonitoring data. The detail of the resrarch contents and results of this article are asfollows:1. The observation well for the roof rainwater recharge is confirmed. The tracertest is an effective method to choose observation wells corresponding to injectionwells based on groundwater measurement and the judgement of the groundwater flowdirection. Take the sodium chloride as tracer, the karst water observation wellslocation, the structure of the karst aquifer and hydrology geology can be confirmed bythe detection of different burial depth groundwater conductivity variation with time.Tracer test results showed that the groundwater flow was northwest by west, that was,from the information building well to west court building well. Buried depth180 meters have good karst fissure. Through analysing the peak value we found two goodkarst fissure channel. The flow velocity of the first channel is20m/h, the second is9.09m/h. Through the tracer experiment we obtained these hydrogeologicalconditions which could be guided to the next step of the karst aquifer roofwaterrecharge.2. The zeolite adsorption performance to ammonia nitrogen was reserched. Afterdetermining the connection among the injection well and observation well, throughthe early rain abandon flow to remove device before6mm with impurity in the earlyperiod of the more rain water, reuse of zeolite in rain impurity ions adsorption effectedto the rain for further processing. The results showed that the experiment of zeoliteNH4+adsorption fit Frundlich formula, adsorption manner was physical adsorption.Two kinds of zeolite adsorption of limit were5.83mg/g and18.375mg/g. Two kindsof zeolite had very good adsorption effect on the pollution of water (rain) of ammonianitrogen, fine zeolite effect had more apparent. But fine zeolite’s particles diameter istoo small, easily through the mesh. So we decided to use thick zeolite in filteringsystem. According to the total amount of rain water filtration system can be containedthe amount of ammonia nitrogen, the biggest adsorption quantity by zeolite canestimate the practice of the total zeolite and design the size of the device. Coarsezeolite experiment of ammonia nitrogen adsorption processes meets level1dynamicrules in25℃, the reaction rate constants for0.21423h-1, the experiment zeoliteadsorption rate constant is0.022212g·m-2·h-1.3. Influences of the natural rain and rainwater recharged to karst aquifergroundwater’ s chemical dynamic changes were analyzed. Monitoring results showedthat natural rainwater effected groundwater by water-rock-air interaction and dilution.Through monitoring roof rainwater and groundwater quality change, it was found thatthrough abandoned flow by the abandoned flow device, and the precipitation byadjusting tank and filtering by filter tank, it could reduce the chemical ionconcentration of groundwater, and it didn’t cause groundwater water qualitydeterioration, but could increase the underground water amount. So as to achieve themultiple purpose of the water supply, the spring protection, and the flood control.