Research On The Influence To The Groundwater Quality Of Infiltration Of Reclaimed Water In The River

The reclaimed water as an unconventional new type of water can ease the tension of water resources and ensure the sustainable use of water resources.But how to use this water safely and effectively has become one of the hot topics in the world.This paper is with the Chaobai River and the Huai River upstream plain of Miyun,Huairou and Shunyi junction in Beijing as the study of the area.The study uses several methods(Single and multiple water quality components comprehensive evaluation,water quality monitoring profiles,isotope technology and the method of numerical simulation)to evaluate the reclaimed water and groundwater quality,and to analyze concentration distribution characteristics of ammonia nitrogen,nitrate nitrogen and nitrite nitrogen.The migration and transformation rules of ammonia nitrogen,nitrate nitrogen and nitrite nitrogen are obtained.The impact degree and current situation influence scope of reclaimed water for groundwater is also concluded.The conclusions of numerical simulation forecast are changes of groundwater level and the impact degree and current situation influence scope of reclaimed water for groundwater.And then forecast warning to the impact trend of reclaimed water for water quality of water source is made.The main research results are as follows:(1)In the reclaimed water quality components,the concentration of TN and TP exceeds the standards.In the organic components,the concentration of chloroform and di-(2-ethyl hexyl)phthalate(DEHP)beyond the EPA standards.In the groundwater quality components,the concentration of ammonia nitrogen,nitrate nitrogen exceeds standards badly.The concentration of chloride ion in groundwater is biggest different from that in reclaimed water.The groundwater quality in the research area is mainly grade ?,but the groundwater quality near the upstream of Chaobai River belongs to grade ?.(2)The time and spatial distribution characteristic of nitrogen is decided by the groundwater flow field,the river seepage control and lithologic structure characteristic.The transformation rule of nitrogen pattern in space and time is also different.Nitrification and denitrification are related to lithology,abundant or dry season change and thickness of vadose zone.In terms of spatial difference of transformation rule,in Miyun reclaimed water intake area ammonia nitrogen in vadose accurs adsorption and nitrification,but the amount of it infiltrates into the groundwater does not decrease.However,in Huairou reclaimed water intake area the amount of it infiltrates into the groundwater is little.The denitrification of nitrate nitrogen in Huairou reclaimed water intake area is stronger than that in Miyun reclaimed water intake area.The nitrite nitrogen of the two intake area from is from reclaimed water or nitrification of ammonia nitrogen.In terms of time difference of transformation rule,the time difference is related to thickness of vadose zone in the abundant or dry season,rainfall leaching and rainfall diluting.The concentration of ammonia nitrogen and nitrite nitrogen is higher in abundant season than that in dry season.But nitrate nitrogen has no obvious change trend.(3)The ?D and ?18O values increase slowly with time,and some values have obvious seasonal.The longer distance from the river,the smaller the values are.The water chemical types in two intake areas are different,which is related to the affection degree by the reclaimed water.But the ?D and ?18O values are stable with time in deep groundwater.The reclaimed water supply ratio in Miyun intake area is related to the distance from river,and the seasonal rainfall do not affect the supply ratio.The reclaimed water supply ratio in Huairou intake area is closely related to the river seepage control.Finally the affected area by the reclaimed water is obtained through above analysis.(4)The numerical model of trend warning mechanism is built,which can show the reclaimed water influence to the groundwater quality of water source.By using the water model,the groundwater level change in the next 10 years of two prediction schemes is predicted.Chloride ion,as the warning index,is simulated and the trend of the affected area by the reclaimed water is obtained.Finally forecast warning to the impact trend of reclaimed water for water quality of water source is made.