High arsenic groundwater has been widely found in many countries in the world, including Argentina, Bangladesh, Cambodia, China, Hungary, India, Mexico, Nepal, Pakistan, Romania, Vietnam, and USA, which has posed a significant health impact on thousands of millions of people. In this short course, a brief introduction to the issue (including world-wide distribution of high arsenic water, aqueous chemistry of arsenic and arsenic-related diseases) will be given. Spatial and temporal variations of groundwater arsenic would change the toxicity of drinking water to human. In order to ensure the drinking water security, variations in groundwater arsenic must be investigated. In this course, a description of spatial and temporal variation will be provided in the West Bengal and the Hetao basin. Biogeochemical processes are critical for arsenic mobilization in the aquifer systems, which will be given in this course as well. In those areas with no low As groundwater available for drinking, technology for arsenic removal is required. Cost-effective technology is preferred due to the low income of the residents in arsenic-affected areas. Adsorption of arsenic on natural siderite and hematite is another topic in this course, as well as adsorption mechanisms.