What is TDS?
Pure water — tasteless, colorless, and odorless — is often called the universal solvent. Dissolved solids” refer to any minerals, salts, metals, cations or anions dissolved in water. Total dissolved solids (TDS) comprise inorganic salts (principally calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulfates) and some small amounts of organic matter that are dissolved in water.
TDS in drinking-water originate from natural sources, sewage, urban run-off, industrial wastewater, and chemicals used in the water treatment process as well as the nature of the piping or hardware used to convey the water. In the U.S., elevated TDS has occurred due to natural environmental features such as mineral springs, carbonate deposits, salt deposits, and sea water intrusion. But other sources may include: salts used for road de-icing, anti-skid materials, drinking water treatment chemicals, stormwater, agricultural runoff and point/non-point wastewater discharges
What is PH?
pH is a measure of how acidic/basic water is. pH is really a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Water that has more free hydrogen ions is acidic, whereas water that has more free hydroxyl ions is basic. Since pH can be affected by chemicals in the water, pH is an important indicator of water that is changing chemically. pH is reported in “logarithmic units”. Each number represents a 10-fold change in the acidity/basicness of the water. Water with a pH of five is ten times more acidic than water having a pH of six.
As this diagram shows, pH ranges from 0 to 14, with 7 being neutral. pHs less than 7 are acidic while pHs greater than 7 are alkaline (basic). Normal rainfall has a pH of about 5.6—slightly acidic due to carbon dioxide gas from the atmosphere. You can see that acid rain can be very acidic, and it can affect the environment in a negative way.