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A2.4      Measures to improve drinking water quality

Where the quality of drinking water needs further improvement, the action to take depends on the parameter and the cause.

Some parameters, such as nitrate or pesticides, relate to human activity in the catchment area. In these cases, measures need to be taken to improve site-specific source protection over a long time. For example, authorities could improve wastewater treatment plants or restrict the use of fertiliser and pesticides within the zone of contribution. They also need to liaise with the teams implementing the river basin management plan under the WFD. Short-term remedial actions could be additional treatment or changing the source of raw water; however, that might require longer water transfers.

For treatment-related parameters, remedial actions include changes in chemical dosing regime, coagulation, clarification procedures, filter operation (backwashing arrangements) or disinfection. Remedial actions related to distribution networks are, inter alia, flushing/scouring the mains or replacing/refurbishing corroded/leaking pipes.

If loss of drinking water quality is linked to the use of materials such as lead, copper and nickel, problems are often related to the domestic distribution network and in-house installation. The only ways to solve them are conditioning the water and informing the public about the proper use of materials and actions they can take to avoid too high levels of those substances in their drinking water.

Figure A2.9 shows the percentages of different kinds of remedial actions for three parameters that cause non-compliance or had a higher number of exceedances in 2011–2013: coliform bacteria, lead and total organic carbon.

Figure A2.9 Remedial actions for selected water quality parameters in the EU, 2011–2013.

Remedial actions for coliform bacteria contamination mainly affect the public distribution network or treatment. Remedial actions to minimise high concentrations of arsenic in drinking water are related to treatment (46 %) or catchment (29 %). For concentrations of lead exceeding the standards, 67 % of all reported remedial actions were replacing or disconnecting lead pipes in the domestic distribution network.

To summarise, specific drinking water quality parameters or groups of parameters cause problems at different points of extraction: water source, treatment, distribution and end of pipe — the consumer. That makes it difficult to develop transparent and useful monitoring, to identify the causes of non-compliance and to implement measures to maintain a healthy supply of drinking water in the EU.