Real-Time Detection of Volatile Organic Compounds in RO-Based Potable Reuse

Collaborative Efforts to Improve Environmental Monitoring
Oral Presentation

Prepared by A. Marcotte1, E. Dickenson2, C. Bellona3, J. Safarik4, M. Plumlee4, V. Rajasekharan5, A. Miller1
1 - Entanglement Technologies, 1192 CHERRY AVE, SAN BRUNO, CA, 94066, United States
2 - Southern Nevada Water Authority, , , United States
3 - Colorado School of Mines, , , United States
4 - Orange County Water District, , , United States
5 - Hach Company, , , United States


Contact Information: [email protected]; 650-204-7875

ABSTRACT

Potable water reuse, especially more direct forms of potable reuse, requires effective treatment technologies and stringent monitoring for chemical and biological constituents of concern. Potable reuse applications commonly employ RO with an advanced oxidation process (AOP) to remove organic compounds. However, a fraction of total organic carbon (TOC) in wastewater effluent makes it through RO/AOP. Of particular interest are organic compounds with low molecular weight that permeate RO, are recalcitrant in AOP, and are of human health. Some of these VOCs would not be detected during chemical peak events by conventional online organic carbon analyzers posing a safety risk to consumers. We have developed a real-time volatile organic compound (VOC) analysis method to detect and speciate specific VOCs of regulatory concern at low detection limits (i.e., nanogram per liter [ng/L]) prior to and after treatment for reverse osmosis (RO)-based potable reuse applications.
This work, funded by the Water Research Foundation, brings together a diverse team including water utilities, academia, and industry. Entanglement Technologies’ AROMA analyzer, a commercially available thermal desorption, cavity ring-down spectroscopy (TD-CRDS) system capable of part-per-trillion (i.e., ng/L), speciated VOC measurements in near real-time, was optimized for application to potable water reuse monitoring and evaluated for long-term, real-time deployments for speciated VOC analysis. The resulting approach uses an online, reagent-less headspace technique providing measurements of 19 VOCs every 50 minutes.
Ongoing work to be presented includes an external, bench-top validation of the analyzer and online use on a 12-gpm pilot-scale closed-circuit reverse osmosis (CCRO) system. Work on the CCRO system will also quantify the RO rejection performance for the target VOCs. Future work includes verifying the feasibility of long-term operation at full-scale and evaluating the VOC analyzers’ performance at pilot-scale with chemical peak simulations at OCWD’s Advanced Water Purification Facility (AWPF). Preliminary data from this deployment will be shared if available by the time of the conference.