A review of in-situ remediation of arsenic in an aquifer

Many communities around the world rely heavily on groundwater for drinking, cooking, washing and irrigation. Sadly, continuing unfettered pumping and withdrawal of groundwater from Pleistocene aquifers have risked high-arsenic groundwater being drawn from adjacent upper Holocene aquifers. Experts have warned that arsenic pollution (particularly of AsIII species) in groundwater poses serious health hazards in several countries where millions of people drink and use arsenic-contaminated water. Due to arsenic-related health concerns in many parts of the world, there is a realization of the need to find solutions for remediating contaminated aquifers and/or groundwater including methods to stabilize arsenic in the soils and rocks. In light of this, a review is undertaken in this paper of the in-situ treatment technologies being investigated to remove arsenic from groundwater, in both laboratory and field settings. Discussion and analysis of the main categories of in-situ treatment methods include (1) passive reactive barriers (PRB) with removal techniques involving surface precipitation and sorption, chemical reactions and reactions with biological mechanisms, (2) chemical oxidation by delivering iron salts and oxidants into aquifers, (3) injection of adsorbent, (4) biological treatment, and (5) artificial recharge. Materials used for PRB technique studies, reactants used for oxidation techniques and parameters influencing the efficiency of the remediation using artificial recharge are also summarized.