What do Total Dissolved Solids (TDS) indicate in a water sample?

Total Dissolved Solids (TDS) serve as an important indicator in water quality testing, specifically reflecting the concentration of dissolved substances in a water sample. These substances may include a variety of inorganic salts, organic matter, and minerals that are completely dissolved in the water. High TDS levels can suggest excessive minerals or pollutants, which could alter the water's chemical balance and impact aquatic life and human health.

In relation to the other options, clarity of the water generally pertains to the presence of suspended solids and other particulate matter, which could affect visibility but does not directly relate to TDS. The pH level of the water, meanwhile, measures the acidity or basicity but does not provide information about the quantity of dissolved solids. Lastly, the presence of microorganisms involves biological aspects of water quality, which is separate from the chemical concentration indicated by TDS. Thus, TDS fundamentally denotes how much dissolved matter is present in a sample, making it a critical parameter in assessing water quality.