Ultraviolet advanced oxidation for indirect and direct potable reuse in California

Abstract

There is high interest in the use of ultraviolet (UV) treatment processes for potable reuse. Advanced and alternative technologies are reviewed at the California Division of Drinking Water. UV is the predominant process used for advanced oxidation (AOP) for projects involved in potable reuse. Potable reuse with and without AOP is discussed. UV AOP is highly effective at inactivating microbiological pathogens and oxidization of organics that pass through the reverse osmosis (RO) membrane. While RO is extremely effective at removing most organic chemicals, there are a few, such as N‐nitrosodimethylamine (NDMA), that are removed at less than 90% because of factors such as low molecular weight. With a high dose of UV, the N‐N bond is broken and thus can be used to degrade nitrosamines, such as NDMA. UV AOP is also highly effective at removing many unregulated compounds such as 1,4‐dioxane and other chemical pollutants that may be found at trace levels in RO permeate.

Predicting the Contribution of Chloramines to Contaminant Decay during Ultraviolet/Hydrogen Peroxide Advanced Oxidation Process Treatment for Potable Reuse

“…Purified municipal wastewater has been increasingly emphasized as a local, reliable source water for drinking water plants. , Potable reuse facilities frequently employ full advanced treatment (FAT) trains, typically including microfiltration (MF), reverse osmosis (RO), and the ultraviolet (UV)/hydrogen peroxide advanced oxidation process (UV/H 2 O 2 AOP), wherein H 2 O 2 is photolyzed to produce hydroxyl radical ( • OH; eq ) to destroy contaminants passing through RO membranes . The ability to remove 0.5 log of 1,4-dioxane, an ingredient in chlorinated solvents and personal care products, , has served as a metric to validate AOP performance . 1,4-Dioxane is poorly rejected by RO membranes, because of its neutral charge and low molecular weight. …”

Introduction to the topical collection on potable reuse

“…Wang et al (2020) used experimental data and modeling results to describe the rejection of several uncharged, polar organic compounds in the context of water‐membrane and solute‐membrane partition coefficients, leading to a conclusion that the most viable way to increase rejection of these important constituents is with denser membrane products, such as seawater RO membranes instead of brackish water RO membranes. For AOP, Bernados (2020) reviewed why these unit processes are an important part of an advanced treatment train for potable reuse, along with commissioning and monitoring requirements.…”