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Preventing contaminant-release into tap water

Over the decades, pipe scale and corrosion products can build up inside water pipes thereby contaminating drinking water. An EU-funded project investigated whether ageing water supply systems could affect the stability of contaminants held in pipes by spontaneously releasing them into tap water.
Preventing contaminant-release into tap water
Low-level release of toxic trace metals such as arsenic (As) and lead (Pb) in urban drinking water distribution systems (UDWDS) are a major issue for tap-water consumers. Although replacing the ageing water distribution pipes will remedy deficiencies in water quality, this measure represents an extremely cost-inefficient form of intervention.

The EU-funded STACS project investigated smart and sustainable control options to address this problem. Researchers began by studying the relationship between pipe scales, biofilms and tap water chemistry with regard to contaminant release in UDWDS.

Important synergistic pipe scale and biofilm conglomerate (SBC) effects on finished water quality were identified. This included factors that promoted chemical release from pipe scale due to the biofilms present at the interface between the pipe surface and water. Scientists also identified the synergistic SBC action behind increased release rates of pathogens or toxins into the water from microbial-enhanced corrosion on pipe scale.

Water quality variables were tested and the main effects and interactions evaluated for four significant variables: trihalomethanes (TTHM), haloacetic acids (HAA), sulphate and orthophosphate. Experiments were also conducted to assess the effect of disinfectants on As release controlled by the dissolution of iron-based pipe scale. This in turn was found to be influenced by the presence of both TTHM and HAA concentrations.

Results demonstrated that increasing chlorination levels during summer in Mediterranean countries could facilitate production of high concentrations of disinfection by-products in tap water, which initiate As release. Water boards should therefore give top priority to such vulnerable areas.

The work of STACS will contribute to the safeguarding of the quality of potable water in EU cities. By preventing contaminant-release into tap water, project efforts will ultimately help guard against exposure to contaminants.

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