Decontamination of biological agents from drinking water infrastructure: A literature review and summary

Abstract

This report summarizes the current state of knowledge on the persistence of biological agents on drinking water infrastructure (such as pipes) along with information on decontamination should persistence occur. Decontamination options for drinking water infrastructure have been explored for some biological agents, but data gaps remain. Data on bacterial spore persistence on common water infrastructure materials such as iron and cement-mortar lined iron show that spores can be persistent for weeks after contamination. Decontamination data show that common disinfectants such as free chlorine have limited effectiveness. Decontamination results with germinant and alternate disinfectants such as chlorine dioxide are more promising. Persistence and decontamination data were collected on vegetative bacteria, such as coliforms, Legionella and Salmonella. Vegetative bacteria are less persistent than spores and more susceptible to disinfection, but the surfaces and water quality conditions in many studies were only marginally related to drinking water systems. However, results of real-world case studies on accidental contamination of water systems with E. coli and Salmonella contamination show that flushing and chlorination can help return a water system to service. Some viral persistence data were found, but decontamination data were lacking. Future research suggestions focus on expanding the available biological persistence data to other common infrastructure materials. Further exploration of non-traditional drinking water disinfectants is recommended for future studies.

The effect of chlorination and hydrodynamic shear stress on the persistence of bacteriophages associated with drinking water biofilms

“…Despite the increasing importance of the ecological and functional roles of biofilms as reservoirs of waterborne pathogens, decontamination data on viruses accumulated in biofilms are still lacking (Szabo and Minamyer 2014). The interferences caused by the biofilm matrix on biofilmassociated viruses during disinfection procedures are generally not taken into account, although the reactiondiffusion interaction of the oxidant leads to poor penetration into the biofilm and slow disinfection progressing from upper to inner zones, as previously shown for biofilm-forming bacteria (Davison et al 2010;Bridier et al 2011;Lee et al 2011;Xue et al 2012).…”

“…). Data on the resistance of viruses in biofilms are much more limited (Szabo and Minamyer ), which therefore makes it difficult to predict the efficiency of traditional cleaning procedures that usually combine chlorination (from a few to 100 mg l −1 of Cl 2 in emergency situations) and flushing at high hydraulic flow rates. Indeed, chlorine is a disinfectant widely used for water treatment, but it has a limited effect against biofilms and pathogens associated with biofilms—even thin drinking water biofilms—as its diffusion is clearly limited by its reaction with the biofilm organic matter and exopolymers (De Beer et al .…”

“…Inactivation by chlorine at concentrations commonly found in drinking water distribution systems (from 0Á1 to >1 mg l À1 ) has already been evaluated for various enteric viruses suspended in water (Engelbrecht et al 1980;Sobsey et al 1988;Abad et al 1994;Thurston-Enriquez et al 2003;Page et al 2009;Cromeans et al 2010;Lim et al 2010). Data on the resistance of viruses in biofilms are much more limited (Szabo and Minamyer 2014), which therefore makes it difficult to predict the efficiency of traditional cleaning procedures that usually combine chlorination (from a few to 100 mg l À1 of Cl 2 in emergency situations) and flushing at high hydraulic flow rates. Indeed, chlorine is a disinfectant widely used for water treatment, but it has a limited effect against biofilms and pathogens associated with biofilms-even thin drinking water biofilms-as its diffusion is clearly limited by its reaction with the biofilm organic matter and exopolymers (De Beer et al 1994;Szabo et al 2006;Wang et al 2012).…”

Photocatalytic biocidal effect of copper doped TiO2 nanotube coated surfaces under laminar flow, illuminated with UVA light on Legionella pneumophila

“…Therefore necessary preventive measures are needed, which in particular include the maintenance of an adequate water temperature at >55˚C, preferably 65˚C with a sufficiently long exposure time, frequent rinsing of pipes, the correct choice of the pipe materials and the avoidance of the long distances. For example, distances between the boiler room and distant taps can be even several hundreds of meters [5,20,21]. Unfortunately, the use of preventive measures does not ensure the long-term eradication of L. pneumophila, which makes necessary to use the combination of several types of measures.…”

Conventional and Alternative Disinfection Methods of Legionella in Water Distribution Systems – Review

“…The main advantages of chloramines are less disinfection byproducts and better inactivation of bacteria in the biofilms [1], [8], [23], [34], [38], which could be a considerable advantage if long distribution system needs to be disinfected. However, long-term…”