The sources of groundwater pollution are many and varied. Pollution by disease causing micro organisms occur when human and animal waste containing virus , bacteria and parasites come into contact with groundwater. Chemical pollutants can leach into groundwater from a variety of sources including hazardous waste dumps, sewage, land-treatment sites, injection wells, indiscriminate solid waste disposal, percolation of pesticides and fertilizer from agricultural field and accumulation of industrial waste water on land.