Oct 12, 2015

Padre Dam Project Incorporates Online THM Instrument

The instrument monitors free chlorine use for potable reuse

Padre Dam Advanced Water Purification Demonstration Project THM monitors

Padre Dam Municipal Water District in Santee, Calif., installed the THM-100 online trihalomethane (THM) monitor from Aqua Metrology Systems to provide real-time data on disinfection byproduct (DBP) formation, aid the utility in evaluating their innovative free chlorine disinfection strategy, and ensure the safety of potable reuse water being used produced at its Advanced Water Purification Demonstration Project.

Padre Dam imports 100% of its drinking water supply from the Sacramento Bay Delta and Colorado River. Drought conditions and imported water supply challenges have highlighted the need for Padre Dam to explore new possible water sources capable of ensuring a safe and reliable drinking water supply. As a result, the Advanced Water Purification Demonstration Project began operations in April 2015 at the Roy Stover Water Recycling Facility to evaluate the treatment strategy needed to meet the requirements for potable reuse from recycled water. Once full-scale, the Advanced Water Purification Project will provide 2,000 to 3,000 acre ft per year, 20% to 25%, of Padre Dam’s drinking water.

The Advanced Water Purification Demonstration Project, using a 100,000 gal-per-day pilot facility, includes the feasibility testing of the addition of free chlorine, ultrafiltration, reverse osmosis and advanced oxidation. Free chlorine is a unique application for water recycling facilities and as such, it is important to test and verify the quality of the potable reuse water created through advanced treatment. The monitor is being used to demonstrate the free chlorine strategy and its ability to provide high quality potable reuse water while limiting the formation of harmful DBPs.

“The THM-100 online monitor provides us with immediate and accurate daily reports on THM levels. Monitoring the real-time formation of THMs helps us to ensure we are meeting the pathogen removal requirements for potable reuse. The online monitor continuously measures the THM levels of the permeate water from the reverse osmosis system. Manually collected samples are analyzed alongside the samples taken automatically by the monitor in its online mode,” said Al Lau, director of engineering for the Padre Dam Municipal Water District.