TDS: TDS in water means total dissolved solids present in water. The amount of TDS in water is a parameter to determine the quality of water. The amount of TDS in water is usually measured in milligrams per liter (mg/L) or parts per million (PPM). According to the Bureau of Indian Standards (BIS), the amount of TDS in water should not be more than 500 ppm. At the same time, according to the World Health Organization (WHO), the amount of TDS in water should be less than 300 ppm. Water with TDS more than 300 ppm is not considered potable. Due to high amount of TDS in water, water becomes salty. When the amount of TDS in water is 65 to 95 ppm, water becomes sweet. However, many important minerals are also removed from it. To reduce the amount of TDS in water, purification systems like carbon filters and reverse osmosis (RO) are used .