Cress Water Solutions - project image

Reed-bed system for single house in Hampshire Area.

Earlier in the last year (2021) we completed the design of a combination vertical and horizontal flow reed-bed system with discharge to a large pond and thence to a soakaway for a client living in the Hampshire area. This is part of an exciting and ambitious self-build project in which the client will be capturing and re-using rainwater for potable purposes as well as filling and maintaining water levels in a large natural swimming pool incorporated into the design of the house. The brief for the project has allowed us to create an attractive aquatic feature within the garden as can be seen from the diagram.

New developments in the Solent Area, which cover a large number of environmentally sensitive and protected habitats, are now subject to severe restrictions regarding sewage discharges to prevent further ecological degradation and eutrophication from occurring. New projects are required by Natural England to put in place methods and systems that will achieve nutrient (nitrate and phosphate) neutrality. The onus is on the developer to implement these rather than the water companies and sewage undertakers. Since we started this project it has transpired that these new rules are being applied in many different parts of the UK where the environment is at risk.

As the new house replaces the one already on the site which discharges to a soakaway Natural England did not require the client to achieve nutrient neutrality with the discharge from the new system as it simply replaces an existing one.  The discharge also comes under Sections 1 and 5 of The General Binding Rules for Small Sewage Discharges and thus did not require an Environmental Permit from the Environment Agency.  However, the client was still interested in reducing the level of nutrients, especially nitrates, in the final discharge.  To do this we included a large pond in the design with a waterfall.  Water in the pond will be continuously recycled over the waterfall enabling some areas within the pond to be aerated and others to be low in oxygen creating ideal conditions for the conversion of nitrates to nitrogen gas and a reduction in nutrients.