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nutrient neutrality

Water Pollution

We use nature based solutions, innovative engineering design together with technology to address nutrient pollution.

Nutrient Neutrality

In recent years much has been reported about the poor ecological status of most of the rivers in England. Only 14% of English rivers have been reported to have a good ecological status. Recurrent years of blue-green algae blooms which negatively impacted extensive areas of nature reserves, wetlands, protected birds and habitats. The high nitrogen and phosphorus concentrations from wastewater effluent and agricultural diffuse runoff. Currently up to 74 Councils are located in affected catchments which has stalled planning on more than 100,000 homes. As Natural England consider that granting of planning permission to new developments would contribute to and exacerbate the the problem. 

Birds At Stodmarsh
Stodmarsh Nature Reserve IX
Stodmarsh Nature Reserve VII
Water Waves
Stodmarsh Nature Reserve VI
Stodmarsh Nature Reserve IV
Stodmarsh Nature Reserve V
Clear Water
Stodmarsh Natutre Reserve II
Stodmarsh at Dawm
Stodmarsh Nature Reserve III
Glasses of Water

The sources of excess nutrients are very site specific but include sewage treatment works, septic tanks, livestock, arable farming and industrial processes. Sewage from new development using waste water treatment works or an on-site package treatment plant that discharges to into local streams contributes to the excess nutrients in the aquatic environment, therefore needs to be considered in line with Habitats Regulations. New developments within the affected areas will now need to be nutrient neutral to avoid detrimental harm to the receiving water body downstream of the development site so that habitat sites are not left in an 'unfavourable condition'.

What is unfavourable condition?

In this context, a site in ‘unfavourable condition’ is not being adequately conserved and/or the results from monitoring show that important features of the site are not meeting all the mandatory site-specific targets.

Environmental Designations 

In many freshwater habitats, rivers and estuaries eutrophication significantly increases the costs of drinking water abstraction and treatment, causes deterioration of aquatic habitats, loss of plants, birds, fish and consequently the loss of biodiversity. It also deters leisure activities like angling, water sports and other recreational activities. Some of the affected areas are Nature Reserves which are designated as a Site of Special Scientific Interest (SSSI), Special Protection Area (SPA), Special Area of Conservation (SAC) and Ramsar Site. Therefore affording them the most stringent environmental protections. 



Habitat Sites

Many of our most internationally important water dependent places (lakes, rivers, estuaries, etc) are designated as protected under the Conservation of Habitats and Species Regulations 2017 (as amended). We call these ‘Habitats Sites’.

In addition some of the affected areas are Nature Reserves which are designated as a Site of Special Scientific Interest (SSSI), Special Protection Area (SPA), Special Area of Conservation (SAC) and Ramsar Site. Therefore affording them the most stringent environmental protections. 

Nutrient Neutral Developments

New Developments can be considered ‘nutrient neutral’ where they can demonstrate that they will cause no overall increase in nutrient pollution affecting specified Habitats Sites.

Developments can achieve this by:

  • On-site mitigation, 

  • Offsite mitigation using a Local Planning Authority scheme or Private Sector nutrient trading scheme located in the same catchment as the development. 

Our Approach


Our approach is to maximise the opportunities for on-site mitigation in order to facilitate a holistic approach that addresses related environmental and infrastructure issues. Typically for onsite solutions we use the following tools as part of our mitigation strategy: 

  • Sustainable Urban Drainage, 

  • Greywater Recycling, 

  • Ponds and Wetlands,

  • Woodlands,

  • On-site treatment works.  

For the offsite solution we have Nutrient Neutrality trading platform that allows developers to register their interest and we match them with credits in our Nutrient Bank.

stodmarsh reserve
residential water recycling


Stage 1: Calculate the New Nutrient load associated with the additional wastewater:

  • Date of installation,

  • The WwTW that it will discharge into, 

  • Number of dwellings, 

  • Whether the catchment of the proposed development has a deductible acceptable loading or not,

  • Apply an occupancy rate of 2.4 people per dwelling. 

Stage 2 - Calculate the annual nutrient load from existing (pre development) land use on the development site:

  • Provide details of the existing landuse cover,

  • Provide details of hydrological characteristics of the site.

Stage 3 - Calculate the annual nutrient load from new (post-development) land use on the development site:

  • Provide details of all the proposed landuse categories post-development. 

Stage 4 - Calculate the net change in nutrient loading for the site and the final annual nutrient budget for the development site:

  • Establish the final nutrient loading of the site. 





Using our innovative Hydraloop Recycling solutions we can reduce the water demand on a new development from 120 l/p/d to 65 l/p/d thus reducing the onsite and offsite nutrient credit requirements by 45%. The recycled greywater treated and disinfected by Hydraloop is suitable for toilet flushing, washing machines, garden irrigation and topping up swimming pools or jacuzzi.

This reduction in credit requirements offers flexibility in delivering constrained brownfield and smaller sites, which cannot achieve nutrient neutrality by onsite measures, which require significant land take.


Achieve 45% Nutrient Credit Requirements with Hydraloop

By reducing the water demand from 125 l/p/d to 65  l/p/d.



Register On
Nutrient Bank

water offsets

Water Offset 

water offsets

To register, please take the time to fill out the information below.

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