Development of an Efficient Method for Hardness Removal from Groundwater

Abstract

Hardness is one of the persistent issues in Sri Lanka related to water quality.It can lead to kidney problems while excess intake of magnesium influences on bowel diseases and laxative effect. Hardness in water is a result of dissolution of limestone - both sedimentary and crystalline - as well as calcium bearing minerals. It can also occur locally in groundwater from chemical and mining industry effluent or excessive application of lime to the soil in agricultural areas. Water hardness has spread almost all over the country. Approximately 75% of Sri Lanka has been affected by water hardness problems. Mainly Jaffna peninsula and several provinces including North Central, Central, Northwestern, Eastern provinces and some areas of Southern province experience water hardness problems (Dissanayake et al, 1985).

Even though, temporary hardness can be removed by boiling there are no efficient methods for removal of permanent hardness in groundwater domestically. Carbonate precipitation is suitable for industrial water softening. But domestically it cannot be applied easily and practically it is not possible. Therefore people tend to consume hard water without any treatment.

The present work aims at identifying and characterizing a suitable low-cost material for water hardness removal.

Methodology

Bentonite clay was used as a hardness removing material. Three experimental methods with potassium dihydrophosphate treatment and Sodium sulphate treatment of bentonite were conducted. Four different concentrations of HCl solutions were used for acid treatment. Other two treatments were done by varying concentrations of the potassium dihydro phosphate and sodium sulphate of each of the four samples. The entire treated sample was centrifuged. 12 samples were then filtered through treated bentonite columns and hardness was measured with EDTA titrimetric method. Finally hardness was measured in hard water passed through the raw bentonite and natural hard water sample to find out the initial hardness in natural water.