GUEST COLUMN: Using TOC analysis to spur safer drinking water

Drinking water treatment plant operators can benefit from using TOC analysis to proactively limit the formation of harmful DBPs.

By Amanda Scott

The U.S. Environmental Protection Agency continues to evolve the Safe Drinking Water Act to protect the public from both harmful microorganisms and disinfectant byproducts (DBPs) in drinking water. DBPs are created when naturally-occurring organic matter, measured as total organic carbon, or TOC, reacts with disinfectants added to control microorganisms present in source water. Several DBPs are suspected carcinogens and are therefore regulated tightly.

Because of the close relationship between TOC and DBPs, it is often said that TOC measured in a water treatment plant today can become DBPs tomorrow. Limiting TOC can greatly reduce the potential for DBP formation. Drinking water treatment plants under the influence of surface water must meet both DBP limits as well as TOC precent removal between source and treated water.

GE's M5310 C TOC Analyzer was specifically designed to simplify drinking water monitoring.

Here are four ways drinking water treatment plant operators can benefit from using TOC analysis to proactively limit the formation of harmful DBPs:

1. Meet effluent quality goals and achieve regulation compliance: Knowing TOC and calculating TOC % removal can not only help utilities meet DBP regulation but also, by measuring and minimizing TOC through the treatment process, helps reduce DBP formation. Over time, plant operators can start to predict TOC to DBP ratios that help them stay in compliance.

2. Make data-driven treatment decisions in real time: With "real time" TOC results, the operator no longer needs to send samples to a lab for analysis, which may take days or even weeks to get results. Real time results allow operators to make immediate treatment decisions following changes in source water quality or changes in process conditions.

3. Monitor overall system health: DBP concentrations can vary significantly throughout a distribution system. The source of this variability is related to the quantity of TOC precursors remaining in the water after treatment, disinfectant contact time, water pH, temperature, and the type of disinfectant used. TOC levels can also fluctuate throughout the year; therefore, many facilities monitor TOC daily in order to optimize their treatment process in real time. Knowledge of TOC through a treatment process can help systems maintain optimal TOC removal efficiencies and protect treatment structures for long term use.

4. Achieve greater process control and optimization: With attention on tighter disinfectant byproducts limits, TOC results from a jar test -- a simulation of the coagulation and flocculation steps in the water treatment process -- provide an advantage in meeting DBP compliance requirements. TOC results can help plants pick the right coagulant dosage and treatment, so they can maximize TOC removal, minimize sludge production, and minimize costs.

At the end of the day, TOC analysis significantly increases the ability to proactively limit the formation of DBPs allowing a plant to not only meet regulation but also better prepare for future use.

About the Author: Amanda Scott is the Municipal Applications Manager for GE Water & Process Technologies.