50 Health and sanitation
Potential water quality issues
In 2016, the US Environmental Protection Agency published Technologies for legionella control in premise plumbing systems: scientific literature review. We extract the sections that are relevant for plumbers in relation to the prevention of legionella.
Chlorine can react with organics, inorganics and non-halogens in the water to form DBPs( disinfection by-products)( USEPA, 2006b).
Some DBPs have been shown to cause cancer and reproductive effects in lab animals and may cause bladder cancer and reproductive effects in humans( USEPA, 2010). In a simulated premise plumbing system of pipe loops, Loret et al.( 2005) found trihalomethane( THM) levels > 100 micrograms per litre(µ g / L), with an applied chlorine dose of 2mg / L. For comparison, the EPA drinking water standard for total THM( TTHM) is 80 µ g / L. Orsi et al.( 2014) noted that special equipment was needed in certain health care settings( for example, dialysis and neonatal care) to reduce free chlorine and THM levels.
Some DBPs are likely to be carcinogenic to humans by all routes of exposure, while others have suggestive evidence of carcinogenicity( NTP, 2006; USEPA, 2005a). For more information about THMs and potential health effects, see the EPA’ s health criteria document for brominated THMs( USEPA, 2005a).
Continuous chlorination at high levels in premise plumbing systems can result in objectionable tastes and odours along with irritation of skin, eyes, and mucous membranes.
Continuous chlorination can contribute to corrosion, with associated leaks, in plumbing systems and may require the simultaneous use of corrosion-inhibiting chemicals. Various corrosion effects have been reported for systems using chlorination:
• Sarver et al.( 2011) reported that continuous hyperchlorination increased leaks by up to 30-fold, consistent with extensive laboratory work in soft higher-pH waters.
• Castagnetti et al.( 2011) found that no high-density polyethylene( HDPE) pipe failure occurred after 2 000 hours of exposure to 2.5mg / L chlorine.
• Hassinen et al.( 2004) studied corrosion in HDPE pipe exposed to chlorinated water( 3mg / L) at elevated temperatures( 105 ° C, or 221 ° F) and found evidence of polymer degradation on the unprotected inner walls of the pipe.
• Loret et al.( 2005) observed similar corrosion marks on mild and galvanised steel coupons installed in pipe loops for various treatment chemicals( chlorine, monochloramine, chlorine dioxide, CSI and ozone).
• Kirmeyer et al.( 2004) reported that higher copper corrosion rates are associated with free chlorine compared to equivalent levels of chloramine; however, this is a site-specific issue.
• In a study by Grosserode et al.( 1993), leaks first appeared in the copper pipes of a premise plumbing system about two years after installation of the chlorine injectors. Significant deterioration was noted only in the hot water system. The addition of silicate corrosion inhibitors reduced the total number of leaks per year by > 80 %.
Operational conditions Parameter conditions indicating operational effectiveness The efficacy of chlorination is affected by many factors, including chlorine concentration, contact time, pH, temperature, turbidity, buffering capacity of the water, concentration of organic matter, iron, and the number and types of microorganisms in the water system( in biofilms and free-living). Lin et al.( 2002) reported that 2 – 6mg / L of chlorine was needed for continuous control of legionella in water systems. The bactericidal action of the chlorine is enhanced at higher temperatures and at lower pH levels. The anti-microbial efficacy of chlorine declines as pH increases > 7, with significant loss of efficacy at pH > 8. However, free chlorine is degraded rapidly at elevated water temperatures, which is a concern for hot water chlorination( Health Protection Surveillance Centre, 2009). Turbidity interferes with the disinfection process by providing protection for organisms; turbidity may need to be reduced prior to disinfection( WHO, 2011b).
Installation considerations Chlorine should be stored in the original shipping containers or compatible containers and sited away from direct sunlight in a cool area. Feed rates should be
April 2017 Volume 23 I Number 2 www. plumbingafrica. co. za