Thinking Outside the Treatment Plant: UV for Water Distribution System Disinfection

Abstract

This work critically evaluates the current paradigm of water distribution system management and juxtaposes that with the potential benefits of employing UV irradiation, which we hope will catalyze a critical re-evaluation of the current practices in water distribution system management and spur critical research and a new way of thinking about secondary disinfection across the extent of distribution systems. Given the recent advances in UV technology and the efficacy of UV disinfection against all pathogen classes, we now see UV applications for disinfection in many aspects of consumers lives: in water coolers, dishwashers, coffee makers, and disinfection of personal items like gym bags, water bottles, and toothbrushes. Public and regulatory concern over water quality and pathogens, especially the recent interest in building plumbing, calls out for new approaches to disinfection and distribution system management. We envision a new model for secondary disinfection in water distribution systems utilizing emerging germicidal UV LED-based disinfection. UV irradiation in water treatment can achieve high levels of disinfection of all pathogens and minimize or eliminate the formation of regulated disinfection by-products. So why is UV not considered as a secondary disinfectant for distribution systems? In this paper, we lay out the logic as to the benefits and practicality of adding distributed UV treatment to assist in protection of distribution systems and protect water quality for human exposure.

Impact of UV irradiation at full scale on bacterial communities in drinking water

“…Not much is known about how a UV installation will affect the biofilm in the drinking water distribution system (DWDS) in the long term 57 . The biofilm community in DWDS is complex and can differ depending on location and material 58,59 .…”

“…A variety of treatment processes produce water containing microorganisms with different UV susceptibility and different wavelengths of UV can be more efficient on certain organisms 76 . In addition to treatment plants, additional applications of UV disinfection include point-of-use and within the pipe network to prevent regrowth of opportunistic pathogens, including UV LED devices 57 . The need to assess the impact of these technologies, both for process monitoring purposes and to investigate the bacterial community that is exposed to consumers through water, could use a molecular biology approach, based on biomarkers for specific taxa.…”

Distributed treatment systems

“…Linden, Hull, and Speight (2019) considered a secondary disinfection system utilizing germicidal UV LED‐based disinfection. Potential locations of UV treatment systems in decentralized and point‐of‐use applications such as storage tanks, pipe walls, and water outlets.…”

Are Secondary Disinfectants Performing as Intended?

“…Compliance sampling for total coliforms reveals that the US has 10 times more positive sample results than the Netherlands, which does not use secondary disinfectants, when adjusted for population (Linden, Hull, & Speight, 2019). Factors such as distribution system pipe age and integrity, along with differences in treatment, compliance sampling and maintenance strategies, affect the compliance rates between the US and the Netherlands, so it is difficult to make a direct comparison based on the effects of secondary disinfection.…”

“…These microorganisms are not regulated in the distribution system and are rarely analyzed at customer taps outside of special investigations, with the de facto control measure being maintenance of distribution system integrity. In the future, implementation of UV disinfection in the distribution system in areas of potential concern might serve as a replacement to secondary chemical disinfectants, particularly given the increasing affordability and accessibility of UV LED technology (Linden, Hull, & Speight, 2019).…”