Which unit is preferred for reporting the concentration of a substance in water or wastewater?

Reporting the concentration of a substance in water or wastewater using milligrams per liter (mg/L) is preferred because it offers a practical and easily understandable measurement in the context of water quality monitoring and treatment processes.

In wastewater treatment, concentrations of various substances, such as nutrients or contaminants, can often range from very low to moderate levels, and milligrams per liter strikes a balance between being sufficiently precise for most applications while remaining intuitive for operators and technicians. Since 1 mg/L is equivalent to 1 part per million (ppm), this unit is also widely recognized and understood in environmental science, providing clarity when discussing regulations and treatment methods.

Other units like grams per liter (g/L) are less commonly used for reporting concentrations relevant to wastewater treatment because the values can become too large and less practical for everyday operations. For instance, a concentration reported in grams per liter might not convey the specific conditions present in a wastewater sample, whereas mg/L easily relates back to smaller concentrations that are crucial in treatment settings.

Micrograms per liter (µg/L) can be useful for measuring very low concentrations, particularly for trace contaminants, but these measurements are often too granular for most routine applications in wastewater treatment. Overall, mg/L is favored due to its balance of precision