UJI KESADAHAN AIR DANAU SINGKARAK PASCA BENCANA

Abstract

Abstract

Lake Singkarak is the largest tectonic lake on the island of Sumatra and plays an

important role as a source of water, fisheries, and support for community activities in

West Sumatra Province. Along with increasing human activities and environmental

changes, the quality of lake water needs to be monitored periodically, one of which is

through hardness testing. This study aims to determine the concentration of calcium

ions (Ca²⁺) as a parameter of water hardness in Lake Singkarak using the

complexometric titration method with EDTA solution. Water samples were analyzed

after EDTA standardization and then titrated using Eriochrome Black T (EBT) indicator

and pH 10 buffer until a color change from wine red to blue occurred as the titration

endpoint. The results showed that the calcium concentration was 48.4 mg per 100 mL,

indicating that the water of Lake Singkarak is classified as low to moderate hardness.

The complexometric titration method proved to be effective, simple, and accurate for

water hardness analysis and can be applied as a monitoring method for the quality of

natural water bodies.

Keywords: Lake Singkarak, water hardness, complexometric titration, EDTA, calcium (Ca²⁺)