The upper River Mun close to Northrepps suffers from chronic pollution. This has reduced the wildlife diversity in the river, and is almost certainly the cause of the periodic death of fish in a downstream lake, Little Broad. Often pollution is invisible, even when quite severe. However, in this case it is plain for the eye to see. Nutrients coming down the stream, predominantly from the Anglian Water sewage treatment works, are causing a condition called eutrophication. This is the extreme growth of plants and algae due to nutrient enrichment. This causes the death of fish and other aquatic organisms in a boom and bust cycle. At the height of algae and plant growth in the spring the water becomes “super-saturated” with oxygen (the oxygen “boom”). As the oxygen tries to force its way out of the water, this causes bubbles to form in blood-vessels of the fish, similar to the condition “the bends” in divers. This causes distress and often death. In the autumn, the algae dies and rots (the oxygen “bust”) and there is now not enough oxygen.
Pollution also has more subtle effects. Elevated levels of nutrients also cause a loss of plant diversity, because dominant “greedy” plants and algae out compete others. A lake (and in some cases rivers) without a diverse plant community is like a rainforest where all but one species of tree are cut down in the sense that this causes a reduction in diversity of all over groups of organisms as well. In short, the upper Mun has a impoverished community of plants and animals due to pollution and this effect is also likely to be passed on down the stream.
After careful planning a design was made to create a wetland to help solve the nutrient problem. We have done this by routing the effluent from the Sewage Treatment Works through a series of wetlands. This would not be possible without the incredible generosity of the landowner who is prepared to sacrifice land in order to help wildlife and improve water quality. The wetland will remove the nutrients by biological and chemical processes. NRT have taken advice from several universities including University College London, Cranfield and Saint Mary’s University in order to ensure that the project delivers maximum benefits.
This 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.
Please read more about this wetland in the EDP HERE.