pH is a logarithmic scale measuring the acidity or alkalinity of water, ranging from 0 (most acidic) to 14 (most alkaline), with 7 being neutral. It is a fundamental parameter in water quality assessment.
The pH of water is a measure of the hydrogen ion (H+) concentration, expressed on a logarithmic scale where each unit change represents a tenfold change in acidity or alkalinity. Natural surface waters typically have pH values between 6.5 and 8.5, influenced by the geology of the watershed, biological activity, and atmospheric carbon dioxide. The EPA's secondary drinking water standard recommends a pH range of 6.5 to 8.5 for public water supplies. Low pH (acidic) water can corrode metal pipes, leaching lead and copper into drinking water, while high pH (alkaline) water can cause scale formation and reduce the effectiveness of chlorine disinfection. Aquatic organisms are generally sensitive to pH changes, with most fish species thriving between pH 6.5 and 9.0. Acid rain, mining drainage, and industrial discharges can significantly alter the pH of receiving waters, stressing aquatic ecosystems. pH is routinely measured in the field using electrochemical pH meters or colorimetric test kits and is one of the most frequently monitored water quality parameters worldwide.