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Hampshire Avon phosphorus reduction challenge

Challenge update Autumn 2021: This blog post contains an update on a scheme we ran in the Hampshire Avon:

This challenge is now closed, but the page will remain to share the challenges that we have previously explored.

If approved as part of our 2020-25 business plan, we’ll aim to improve the river water quality in the Hampshire Avon catchment by reducing levels of phosphorus in the water.

We’re looking to the market to suggest new ideas for doing this – can you help?


We work constantly to protect and enhance the environment.

We’ve an excellent environmental compliance record across our region, are one of the industry leaders when it comes to catchment management and have developed the innovative environmental trading platform EnTrade.

In the Hampshire Avon catchment the Environment Agency (EA) and Natural England (NE) are concerned about levels of phosphorus (P) in the river and would like to see an improvement. Phosphorus is a plant nutrient and elevated concentrations can lead to excessive growth of algae and other plants. It reaches the river through a variety of routes; discharge from sewage treatment works, industrial discharges, agricultural run off and naturally occurring sources such as the local geology to name a few.

The impact on the composition and abundance of plant species can have adverse implications for other aspects of water quality, such as oxygen levels and the characteristics of river habitats. The various changes can cause undesirable disturbances to the balance of plants and  animal life in the river, such as invertebrates and fish.

Water recycling centres’ (WRC) discharge permit limits are set to fulfil the requirements of the Water Framework Directive, and other legislation. Our WRCs reliably achieve their phosphorus permit limits, often seeing improvements of up to 50% in the discharge quality beyond that needed by their permit.

We have agreed with the EA to see whether, during 2020-25, there are alternative ways to improve the river water quality in the catchment instead of adding additional treatment on our sites, which would likely be at significant cost and have a negative impact on other environmental areas such as carbon.

More information can be found in our business plan –  appendix 3.1.A, pages 237 to 246.

We want to work with others to see if there are alternative suggestions to improve the P levels in the catchment.

How can you help?

We’ve a few streams of work in place already:

  • we’re looking to improve the performance of our WRCs and their P removal rates, by further optimising our existing assets where we can do so without significant capital investment
  • we’re looking at working with farmers in the catchments to see if there are land management measures we could implement with them
  • we’ll be talking to our trade effluent dischargers to see if they are able to help reduce their P loads
  • we’re looking at whether wetlands might have an impact on reducing P levels.

However, we know those won’t be the only answers.

We want to know if you have any other suggestions for how we could reduce P levels in certain areas of the catchment as we’re interested in working with partners to fund additional P reduction measures.

The map here shows the river stretches where we are keen to target P reductions. The orange hazed areas show the areas we are particularly interested in exploring whether we could fund any phosphorous reduction improvements.

In particular, the tributaries before they meet the main river are likely to be of interest as measures will have a bigger impact on the water quality in a smaller body of water.

We’ve published our WRC influent and effluent quality data, discharge permit data, flows and data we have on river water quality, as well as linked to the EA information they have for water quality in the area.

Get involved

We’ll be holding an information session so you can hear more about what we’d like to do and how we want to engage. We’ll give an overview of the performance commitment, more information on what we’re already doing, how we want to work with partners and the process for engaging, with the opportunity for you to ask us questions.

This session will be at:

Wessex Water Operations Centre, Claverton Down, Bath – 10am – 1pm, 17 May

We’ll have around 90 minutes of general presentations and then our staff will be on hand to answer any specific questions attendees may have. Please note, we won’t be able to discuss proposals in any detail with attendees at this session.

Please email [email protected] to sign up to attend these sessions.


We’ll then be asking for organisations to send us any suggestions they have for P reduction in the green lengths of river indicated on the map above. Please send them to [email protected] by the 21st June giving as much information on the following questions as possible.

  • What’s the solution you’re proposing?
    • Please describe how this solution reduced P levels and what amount it is expected to remove
    • what evidence base (scientific or otherwise) is there to support the P reduction in the river?
  • What do you believe will be the likely P impact and where?
  • Has your solution any form of regulatory approval?
  • About your organisation – what previous experience do you have in this area.

While we’re interested in all ideas for P reduction, we’ll need solutions to have had some form of proof of concept for us to be able to consider them for implementation. However, we are interested in hearing about the latest research and thoughts in that area as these may have potential.

We’ll review the solutions received by 31 July and see if there are any that may be viable, creating a shortlist of ideas that we would like to explore further.

Important points

  • The proposed solution must have an impact on P levels in the river in the green stretches highlighted in the map above.
  • Our AMP7 business plan is under review with Ofwat, the economic regulator for water and sewerage services in England and Wales. Ofwat’s final determination of our AMP7 plan will be made in December 2019, and this performance commitment cannot be confirmed until then. We are, however, still keen to explore options.
  • Please note that we are not committing to contract with any party to reduce P levels in the river and are just exploring the possibilities at the moment. If appropriate solutions are identified, a formal tender process may be required. All parties who express an interest in being involved will be contacted if and when this has begun.