Ms Angela Ryan:

That is a type of network intervention we can use. When we assess our networks, loads and capacity for new connections, separating systems is one of the options we have.

With respect to where things are going, with the recast urban wastewater treatment directive that is being developed in Europe, the new approach to this is to stop rainwater getting into all the systems in the first place. As part of the new directive, we expect to see the requirement for integrated wastewater and drainage plans for larger agglomerations. Those integrated wastewater and drainage plans will look to progress nature-based solutions, such as holding water, soaking it into the ground and not letting it get into the surface water or sewer networks in the first place. There is an important nuance there as well. Rainwater that falls on the ground, particularly in urban areas, even when it gets into the surface water network and discharges to a river, is dirty water, so it has an impact on the receiving water body.

There is a gain to be had from preventing it getting into surface water systems and foul systems – combined systems – in the first place.