EVALUATION OF GROUNDWATER QUALITY : LABORATORY STUDIES

Abstract

The quality of groundwater depends on the characteristics and type of the subsurface soil and nature of the recharge water. Water applied at the ground surface in the form of rainfall and irrigation has to pass through unsaturated zone before reaching the water table. Water in contact with sediment material may result in leaching out of more soluble species, precipitation of saturated species and the formation of colloidal oxides via chemical reactions such as acid-base reactions, complexation reactions and oxidation-reduction reactions. In the present Study, an attempt has been made to understand the nature and extent of interaction of recharge water with soil and flyash for which bench scale batch tests and column tests have been carried out. The soils used in this study was collected from agriculture field and campus soil. The flyash sample was taken from NTPC, Dadri (Ghaziabad).Flyash and soil properties like grain size distribution, dry density, moisture content, permeability, pH and organic content were determined.The recharge waters used in this study were distilled water, tap water and the wastewater. During preliminary test, a batch study was performed to know the time of attaining the equilibrium state between the soil and recharge water. On the basis of time response results, the other batch studies of combination of soils and flyash with different recharge waters were conducted. PVC column was used to study the influence of flow rate on water quality. Distilled was allowed to pass through the soil column continuously keeping the head constant. From the batch study and column study it is concluded that the characteristics of tap water do not change significantly on equilibrating with campus soil and agriculture soil. Flyash appears to have higher leaching potentials. The leaching characteristics depend on nature of soil as well as the characteristics of water in contact with the soil. From the column test it is observed the decreasing trend of water quality parameters with time.At low flow rate, the material initially leached at high rate and gradually the materials leached tends to be exhausted.