In Welsh Water, we already use natural processes to help treat our waste water at many of our sites. For example we have reedbeds and biofilter beds, both of which rely on bacteria to effectively break down any pollutants that exist in the wastewater. But we have some exciting plans to use constructed wetlands as an additional solution to further treat wastewater, before it is returned to the environment.

Constructed Wetlands are engineered to mimic the physical, chemical, and biological processes occurring in natural wetlands. Wetlands work by taking partially treated wastewater and passing it through a series of interconnected ponds. All the ponds are planted with native aquatic species such as iris, rush, marsh marigold and watercress.

The wetlands naturally remove ammonia, nitrogen and phosphate. Wetlands are a much needed solution for some of our smaller wastewater treatment works where conventional solutions may not be possible, or may be too expensive or too carbon-intensive infrastructure . Wetlands also create fabulous rich habitats for local wildlife.

Where we’re working

Welsh Water is currently progressing a number of partnership wetlands with councils in England. We also have 6 site at feasibility stage for wetlands as part of our next 5 year investment programme (AMP8), also in England where there is a wetlands regulatory framework in place. In Wales, there are 2 trial wetlands we are currently in discussions with our Environmental regulators (NRW) about. We hope DCWW’s 2 trial wetlands in Wales can support a suitable regulatory framework to enable more Wetlands in future years. Most of these sites have new phosphorous targets, which is what the wetlands will be designed to treat. But some of the wetlands will be targeting ammonia, and others are to help store and treat storm water.

All of them will be progressed as trial wetlands, which means we will be running research projects along side them, so we know every step of the way how they are performing and what benefits, and potentially what disbenefits, they provide. This information will help us understand where else we can use wetlands to address water quality issues.

See where we are working in your area.

How we assess if a wetland is suitable

Wetlands aren’t a new approach, they are natural process after all! Many countries have been using wetlands and reedbeds for many years to improve water quality. But they are still an ‘unproven’ approach in the water industry in the UK, with only a handful of examples for us to learn from. We are working with our academic partners in Cranfield University, Cardiff University and others, to increase our understanding of how wetlands work, and what the optimum maintenance regime is.

From what we already know about wetlands, we are able to screen in and screen out wastewater treatment works based on certain rules. These rules include:

  • The size of the treatment works. Larger sites that serve more than 2,000 population would probably not be suitable for a full flow wetlands, due to the surface area needed
  • The permit limits of some treatment works would be too low for a wetland solution to provide the standards we require
  • Some of our sites receive trade effluent from a business or industrial processes. Sometimes this trade effluent contains chemicals that would harm a wetlands, and prevent the wetlands performing the best treatment process. Find out more about trade effluent here.
  • Some of our urban sites might not have the space available for a wetlands

It is important for us that we provide the right solution, in the right location. Some instances this will mean a conventional solution will provide the best benefit.

Collaborative Wetland Opportunities

Historically, most sectors used to work in isolation, but recently, we have come to recognise that to truly address water quality and other environmental problems long-term, we need to collaborate. A Catchment Based Approach, initially launched by Defra in 2013, demonstrates the benefit to all stakeholders of improving the water environment through catchment-level engagement, planning and delivery. The aim of Catchment Based Approach (or CaBA) is to balance environmental, economic and social demands and align funding and actions within river catchments to bring about long-term improvements. Read up further on the CaBA here.

The Catchment Based Approach encourages organisations to manage land and water in an integrated way, by identifying the pressures on the water environment, recognising the potential for conflict between the interests of users (from industry to farmers, from anglers to canoeists, from local people who want to be able to access to the waterside to ecologists keen to preserve fragile habitats) and working together to agree common objectives and implement solutions. CaBA are a long term goal, and will take time to develop.

Due to the multiple benefits a wetlands provides, and the fact that each wetland is made up of multiple individual ponds or ‘cells’, they provide a good opportunity for collaboration. For this reason, we have provided a list of collaboration opportunities to all councils and nutrient management boards. Read more about collaborative wetland opportunities here.

What’s the need?

We have permits in place at our wastewater treatment works to protect the river and our seas. These permits are set by our environmental regulators and can be changed by them when needed, to reflect the changing needs of the river, or if new evidence is found. When this happens, we work with our regulators to improve and upgrade our treatment works. Historically, the water sector has often focused on engineered solutions when designing treatment work improvements. This is largely because we need to provide our regulators and our customers with confidence that the water quality improvement will be met from day one of the solution being installed.

In recent years, we, like other water companies are starting to have tighter permit limits on some of our smaller, more rural wastewater treatment works. These small treatment works are often not suitable, for a large engineered approach, with complex maintenance requirements. We need smaller and more sustainable treatment approaches.

Why wetlands?

As well as providing water treatment benefits, wetlands are a rich and valuable habitat for biodiversity. They are provide an additional community benefit as they act as an amenity space and educational site for local schools. Depending on the site of the wetlands and the land footprint required, they are often a lower cost solution compared to conventional engineered approach, and don’t require external chemicals and most of the time require zero energy demand.

Although a wetlands will not always be suitable, where they can confidently provide the water quality needs, we commit to working with wetlands and other nature based solutions, for the benefit of our rivers and biodiversity.