Padre Dam Advanced Water Purification Demonstration Project Incorporates Online THM Instrument To Monitor Free Chlorine Use For Potable Reuse

Padre Dam Municipal Water District in Santee, California has installed the THM-100 online trihalomethane (THM) monitor from Aqua Metrology Systems to provide real-time data on disinfection by-product (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 their Advanced Water Purification Demonstration Project.

Padre Dam imports 100 percent 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 feet per year, 20-25%, of Padre Dam’s drinking water.

The Advanced Water Purification Demonstration Project, using a 100,000 gpd 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 THM-100 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, Padre Dam Municipal Water District.

“As utilities explore new potable water sources, such as potable reuse, or new technologies to improve existing water quality, it is imperative to validate performance during feasibility studies and full-scale operation,” said Rick Bacon, CEO of Aqua Metrology Systems. “Online instruments such as the THM-100 provide utilities with the high frequency and real-time data needed to safely and effectively manage their water, water reuse or wastewater treatment facilities.”