Monitoring dissolved organic carbon in surface and drinking waters.

Area of Science:

• Environmental Science
• Water Chemistry
• Public Health

Background:

• Natural organic matter (NOM) is a critical factor influencing drinking water treatment efficacy, final water quality, and its behavior within distribution systems.
• Understanding the dynamics of NOM is essential for optimizing water treatment processes and ensuring safe drinking water.

Purpose of the Study:

• To quantify the daily concentrations of dissolved organic carbon (DOC) in river water before and after conventional treatment over a 22-month period.
• To investigate the relationship between variations in organic matter (quantitatively and qualitatively) and environmental factors like precipitation, runoff, seasons, and operational conditions.
• To determine the average removal efficiency of organic matter during conventional drinking water treatment.

Main Methods:

• Utilized an on-line total organic carbon (TOC) analyzer for continuous daily monitoring of DOC levels.
• Collected and analyzed water samples from a river source over a 22-month duration.
• Correlated DOC, color, UV absorbance, and turbidity data with precipitation, runoff events, seasonal changes, and treatment plant operating parameters.

Main Results:

• DOC concentrations in river water exhibited significant fluctuations, increasing up to 3.5-fold after rainfall events compared to baseflow.
• Associated increases in water quality indicators were substantial: color (8-fold), UV absorbance (12-fold), and turbidity (300-fold) following rainfall.
• Conventional drinking water treatment achieved an average removal of 42% of organic matter, with treated water DOC levels directly reflecting source water quality.

Conclusions:

• Precipitation and runoff are major drivers of natural organic matter variability in river water, significantly impacting raw water quality.
• Conventional treatment processes demonstrate a moderate but consistent capacity for removing dissolved organic carbon.
• Source water quality is the primary determinant of treated drinking water DOC levels, highlighting the need for robust treatment strategies adaptable to changing environmental conditions.