Hydrochemical Characteristics Of High Arsenic Groundwater In Northwestern Heteo Basin And Proper Technologies For Arsenic Removal

High As groundwater occurs in many provinces of China.Hangjinhouqi county is a serious endemic arseniasis area.It is necessary to develop economic and effective methods to remove As from arsenic-contaminated water.The study area is located in the northwestern part of the Hetao basin,Inner Mongolia.To investigate the hydrochemical characteristics and As removal technologies of high As groundwater,field work and laboratory experiments have carried out.The main conclusions in this study are shown as follows.Concentrations of total As range from<1 to 367?g/L.From the mountain to the flat plain,groundwater As concentrations increase.There are significant positive correlations between As and Fe,Fe²⁺,HCO₃^-,NH₄⁺.Under anoxic conditions in aquifers,the reductive dissolution of Fe?III?/Mn-?hydr?oxides with adsroded As and the reduction of strongly sorbing arsenate to less strongly sorbing arsenite result in elevated concentrations of dissolved As?III?in groundwater.Coprecipitation experiment results reveal that concentration of dissolved iron in groundwater is the decisive factor for As removal.Fe/As?w/w?ratios of?250 are required to ensure As removal to levels below 10?g/L.However,P strongly competes with As for uptake by Fe?III?-precipitates,while Ca promotes As removal by precipitates.Natural siderite?NS?and three oxidants are used to investigate characteristics and mechanisms of As???removal from aqueous solutions.Results reveal that the type of oxidants and concentration have different effects on As???removal.Taking cost and secondary pollution into account,the best strategy to strengthen NS is 0.3 mmol/L NaClO.Modified granular natural siderite?MGNS?is used to investigate the fixation of groundwater As in Shahai town.Column tests show that there is a significant difference in breakthrough curve?BTC?between aerated groundwater and fresh groundwater.The main factors might include initial As concentrations,coexistence of ions,and temperature.Hydrochemical characteristics of high As groundwater play an important role in As removal.Remediation of As-contaminated groundwater should be based on the hydrochemical characteristics.Arsenic co-precipitation with Fe?II?oxidation is suitable for groundwater with high initial Fe/As?w/w?ratio.When high As groundwater with high concentrations of competing anions,modified natural siderite may be better for As removal.