Study of Movement of Pollutants in Soils around the Onsite Sanitation Systems - A Case Study of Periurban area in Karnataka, India

Abstract

Sitting onsite sanitation systems near ground water sources without following any Indian national building organization, guideline is common in the peri urban areas in India. Due to close location of them the contaminants infiltrates from onsite sanitation systems and causes contamination of groundwater sources. Contamination of groundwater sources by pathogenic bacteria and nitrate are two major public health risks due to onsite sanitation systems. Sufficient depths of unsaturated soil and adequate horizontal separation distances between an onsite system and water sources are required to protect public health from aquifer contamination. In the present study the assessment of movement of pollutants in sandy soils around the onsite sanitation systems has been carried out to study the impact of septic tank on nearby borewell groundwater. Soil samples were collected around the septic tank in five directions. In each direction, soil samples were collected at 1 m interval longitudinally up to 2 m from septic tank edge at 0.3 m and 0.5 m depth. The soil samples are analyzed for sulphates, chlorides, phosphates, nitrates. The soil samples for bacterial analysis (E. coli) were collected in both monsoon and non-monsoon seasons upto 10 m from septic tank edge. From analysis of soil samples it can be concluded that concentration of nitrate, chloride, phosphate and sulphates leached from septic tank are not able to effect quality of bore well water located downstream of septic tank. The E. coli movement in the soil is observed upto 5 meters from the edge of the septic tank. The study concludes that the present distance between public borewell and septic tank is sufficient to prevent groundwater contamination.