Integrated wetland project on the River Mun reduces phosphates from sewage effluent

As the second shortest river in Norfolk, the 'Mighty Mun' may sometimes struggle to live up to its grandiose nickname.

But this tiny, unassuming waterway could become a trailblazer for a new method of reducing the phosphate levels in effluent legally discharged from the county's sewage treatment works.

A pilot 'integrated constructed wetland' has been created alongside the Mun, as it runs through the Templewood Estate near Northrepps.

Three shallow lagoons were dug in October, and filled with 18,000 emergent aquatic plants, with the help of 30 volunteers from the neighbouring villages.

The uppermost of these 'cells' receives the output piped directly from the Northrepps Sewage Treatment Works – only 250m away – and cascades it through each subsequent lagoon, with the plants and silt trapping the phosphates before returning the water to the river.

Project managers claim the new wetland is removing about 90pc of phosphates which would otherwise be fertilising the rapid blooms of algae which were choking the life out of the river.

As a result, they have recorded a huge increase in wildlife, including a 700pc leap in Red and Amber-listed protected birds, and 16 species of dragonfly.

The scheme is the result of a partnership between the Norfolk Rivers Trust (NRT) and the landowner, former ITV producer Eddie Anderson, who lives at Templewood House and owns the first mile of the river.

Jonathan Lewis, project officer for the NRT, said: 'These integrated constructed wetlands were pioneered in Ireland 30 years ago. This is the first one in Norfolk and we are pioneering it as a natural, sustainable method which could bring both economic, ecological and community benefits.

'The treated water is cleaned to human standards of safety, but the standards for wildlife are very different. In terms of algal growth, to have so much phosphate in there is like chucking a load of Miracle-Gro in the river. It creates this boom-and-bust of oxygen and the rapid amount of plant growth.

'The wetlands are filled with these emergent aquatic plants, and the initial gain from them in term of phosphates is not much – they take it up, but then they put it back when they die in the winter. But they bind it into the silt and they provide a complexity to the way the water flows through the wetland. One layer is aerobic, so there is oxygen there, but there is an anaerobic section as well and it is that combination which traps the phosphates and allows the aerated water to move through.'

Mr Lewis said the initial response from wildlife had been 'amazing'.

'It has been far more than we thought,' he said. 'In the first 24 hours we had a dragonfly laying its eggs and in 10 months we have seen birds like the cuckoo, whitethroat, kingfisher, snipe, and 16 species of dragonfly. We have had otters, badgers, roe deer, a fox – and water voles moved in within a day.'

Mr Anderson said he had been impressed by the community involvement in the project.

'The river touches seven parishes and everyone along the river has shown an interest,' he said. 'This is a tiny set-up, but it is the first in the UK so it is a model we could see more often.

'One of the designers was a hydrologist and he said this is 16pc of the cost of a traditional phosphate-stripping device, and 23pc of the running cost. If you can find a bit of land that is flat and low enough to take this water, it is a no-brainer.

'I have another reason for wanting this to happen, We have a one-hectare lake that's right in the middle of the wood, which has been destroyed by eutrophication, due to the algae that has grown profusely with the nutrients in the water – and most of that is phosphates from the water treatment works. Anglian Water is treating the domestic sewage from Northrepps and what they put into the river is completely legal, but we know it is not clean. But we cannot just say Anglian Water is responsible for polluting the river, and we want to establish and confirm good relations with them.'

The project was visited on Thursday by North Norfolk MP Norman Lamb, who said: 'It is an amazing project. They are demonstrating what is possible and what could be done in lots of other locations to improve the quality of water in our rivers.

'The 90pc reduction in phosphates is incredible, but it also indicates that the existing legislation is flawed. Anglian Water can say they are meeting the legislative requirements – and they are – but is that generating clean and healthy rivers? It is not.

'Just looking at the watercourse here demonstrated the impact of phosphates coming out of sewage, so it seems to me that there is a case for amending the European directives to require this kind of approach to be taken elsewhere. There could be a big environmental gain at very little cost. There has been a big increase in bird life, which is very exciting, and I am very keen for Anglian Water to work very closely with the Norfolk Rivers Trust to achieve similar gains elsewhere in the county.'

Water company viewpoint

Anglian Water said simply reducing phosphate limits in treated water was not an option under EU guidelines which put the emphasis on more sustainable ways of improving the health and ecology of rivers.

New regulations coming into force in 2017 will limit the amount of phosphates in household items such as dishwasher powders and household laundry detergents, reducing the amount of the chemicals getting into the water in the first place.

Emma Staples, from Anglian Water, said such measures, allied with community projects like the one at Northrepps, could be part of the long-term solution.

'It sounds like they have done a great job to attract wildlife to the site,' he said. 'The situation with phosphates is quite an interesting one. It comes from household detergents, shampoos and washing powders, and as a result it is due to be limited in certain products by 2017.

'We do treat for it and we remove as much as possible to comply with the regulations that are set, but the EU Water Framework Directive (WFD) says we are not allowed to simply add more treatment to bring the levels down.

'Any type of treatment is expensive and has big energy costs and big environmental costs, so the WFD is essentially saying that carbon-expensive treatment processes are not sustainable for the long term. So we need to look at more sustainable ways of looking at water quality. That is the premise that underpins the catchment management approach which we are working on nationally with the Rivers Trust.

'So community projects like the one at Northrepps are to be applauded. Those community initiatives are going to be really key because they are a generally sustainable way to solve the problem. We are keen to support that kind of work.'

The 'Mighty Mun'

• The River Mun, also known as Mundesley Beck, flows through seven parishes – rising in Northrepps and ending at the North Sea at Mundesley.

• At only five miles long, it is the second shortest river in Norfolk, behind the Thurne.

• Geologically the river is about 450,000 years old and was created when the Anglian glaciation created the eastern end of the Cromer ridge. A river valley was formed to the south by fast-flowing glacial melt waters, depositing gravels and clay.

• The first written references to the river appear in 1082 when William the Conqueror drew up the Domesday Book.

• Four mills were recorded in Northrepps, Gimingham and Mundesley, which could only have been powered by the river.

• Many archeological finds from the Mun valley reveal there was human occupation in the area since the Neolithic to the Bronze Age and through the Roman, Saxon and Medieval periods to present day.