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Nutrient Neutrality

Here to help: If you need a Nutrient Neutrality Report please email for a quotation phone numbers are at top of page if you prefer.

If you are looking for a Phosphate Assessment please visits our Phosphate Assessment Page.

This page is relevant if you have been asked for a "Nutrient Neutrality Assessment and  Mitigation Strategy (NNAMS)", as per latest validation requirements from Somerset District Councils such as Mendip.


In attempts to reduce nutrient loading to SSSIs and RAMSAR Sites such as Stodmarsh SSSI and Somerset Levels & Moors RAMSAR, Natural England (as consultees on planning applications) are asking for all development upstream of these protected sites to prove Nutrient Neutrality.

Nut Shell: New housing by example, will mean more new people using the toilet. The nutrients from this waste enter rivers or ground water via a local or district sewage treatment plant. The nutrients can then travel down stream, and cause problems at protected "nature reserves". One such problem is that too much nitrogen or phosphate might cause an algal bloom that turns clear water, murky and can prevent animals living in the water, or harm those that are already living there.

Origins of Nutrient Neutrality

Natural England may request a Habitats Regulations Assessment (HRA) due to the recent CJEU Dutch Nitrogen case law. The Dutch are taking nitrogen pollution so seriously that they have even cut motorway speed limits to 62mph, to reduce nitrogen oxide emissions. Efforts to become nitrogen neutral in Holland, have effectively paralyzed many major projects.


The solution will depend entirely on the source of nutrients. In the UK the most popular enquiry we receive is for new housing, in Taunton and Bridgwater (Towns in Somerset). Here developers seeking to build new homes are asked to prove no impact on down stream receptors such as Somerset Levels & Moors RAMSAR. The reporting structure is of a Habitats Regulation Assessment.

The below solutions must be set up in the same catchment as the affected protected site. So for example for the Somerset Levels & Moors RAMSAR, the project would have to be set up on the River Tone or River Parret (or tributaries of these rivers). The offset does not have to be on site.

Package Treatment

To complete the Habitats Regulations Assessment information on how foul water is to be dealt with, this will either through a mains wastewater treatment plant or a site package treatment plant or septic tank. If it is via the main wastewater network the Wastewater Treatment Works, and the amount the permitted amount of phosphate for the works. Where Package Treatment Works information on the efficiency of the plant in treating phosphates will be required.


Nutrient Neutrality Woodland Example: 8 Hectares of Woodland would "offset" nutrients from approx. 24 new homes. This is quite a lot of area, but consider that woodland can also be used for other purposes, such as timber, or bio-diversity offsets.

The above 24 homes figure is referenced by RSK in their recently published Rewilding Guide.

Constructed Wetland

Nutrient Neutrality Constructed Wetland Example: 0.5 Hectares of Constructed Wetland would "offset" nutrients from approx. 24 new homes. Wetlands offer one of the best NPK removal rates by area. We have conducted research in to methods uses in Scandinavian counties (Sweden), as they have been dealing with this problem for many years, whilst the UK has fallen behind.

Small Scale Thresholds

You may not need to undergo mitigative measures, if you site meet requirements of small scale thresholds.


Costs for scheme will vary depending on scale, and nutrient loadings but are likely to start at around £10,000 based on on site treatment plant. Factoring in land costs and setup costs for constructed wetland, the costs are likely to be much higher.

Areas around the UK where Nutrient Neutrality is an Issue

There are numerous areas around the UK, where Nutrient Neutrality is a major planning hurdle to overcome. They include:

Constructed Wetlands for Nutrient Neutrality

For new homes built on agricultural land, it will be possible to balance some of you nitrates and phosphates originating from the development, with the reduction created by taking agricultural land out of production.

The remainder of the nitrogen or Phosphate will have to be passed through a specifically designed reed bed system, or constructed wetland.

A constructed wetland, is an area through which water can flow that is planted with reeds (Phragmites australis), studies have shown that this provide extremely effective phosphate removal (95%) and very good nitrate removal (85%).

Image below shows Flintenbreite constructed wetland, in Germany (Creative Commons - Nelsnelson).

Flintenbreite constructed wetland

How can SWEL help with Nutrient Neutrality?

SWEL can prepare all of your required reporting, to get you through planning. We can also help set up constructed wetlands (habitat creation), and already have an agreement in place with a land owner in the Tone, Parrett catchment for provision of land close to a water course, for construction of wetland habitat.

Which Developments Require Nutrient Neutrality Assessment?

Most standalone developments that introduces nutrients to the environment will require assessment, if they have the potential to affect a designated site such as a SSSI. These might include:

However, some smaller developments such as residential extensions, and residential annexes may be exempt. A further list provided from official Somerset County Council Guide.

Rationale for Nutrient Neutrality Assessment

The following bullet points outline the rationale for making assessments for nutrient neutrality. Further details available in Interim guidelines on small scale thresholds and nutrient neutrality principle for the Somerset Levels and Moors Ramsar catchment. V.1: 28/01/21

Phosphate Budget Calculators

Somerset have release a Phosphate Budget Calculator, and Natural England have a basic calculator for Nitrates. Cornwall Council are soon to release their own budget calculator.  The regional variations have many similarities, but they do require a list of Waste Water Treatment Works specific to the region.

The wastewater nutrient budget calculator can be provided by the LPA on request, if not otherwise supplied with this guidance document.

No mitigation required

If the Phosphate Budget Calculator results in a zero or minus nutrient loading figure, then the need  or mitigation is negated. Please submit the calculations within the provided spreadsheet for the LPA to review and confirm next steps.

Mitigation required

If the Phosphate Budget Calculator indicates a net nutrient loading from the proposed development,  then mitigation will be required.

For further guidance please see Somerset Nutrient Information Request Sheet_V1

Phosphate Credits for Sale

There is a possibility that we can make Phosphate Credits Available, or can help you "make" your own. More Information on Phosphate Credits