The role of wastewater treatment in the nutrient neutrality equation

Nutrient neutrality planning requirements are still in place in parts of the UK to protect natural areas. These planning requirements are a challenge for developers looking to build new homes.

In this blog post, we explore the impact of nutrient pollution, the nutrient neutrality concept, and how onsite wastewater treatment can play a significant role in the neutrality equation.

Nutrient pollution 

Nutrient pollution is a major environmental issue for many natural areas in England. Increased levels of nutrients (mainly nitrogen and phosphorus) can build up in freshwater habitats and estuaries and speed up the growth of plants. This process, known as 'eutrophication', degrades the quality of water and harms wildlife. 

The impacts of nutrient pollution can be found in streams, rivers, lakes and coastal waters. Overgrowth of algae consumes large amounts of oxygen that fish and other aquatic animals need to survive. And the water becomes cloudy, making it hard for them to find food. These toxins can also cause harm to other wildlife that drink or bathe in the water.

There are health risks for humans that come into contact with the water too. Certain algae emit toxins that can cause stomach aches, rashes and more severe problems.

Causes of nutrient pollution

Increased nutrients tend to come from sewage treatment works, septic tanks, or agricultural run-off, where intensive livestock farming produces harmful chemicals from animal waste and fertiliser.

But new housing developments can also add to the problem. Where nutrient pollution has already caused unfavourable conditions, the extra wastewater from new developments can worsen matters and impede ongoing efforts to recover these sites.

The law around nutrient pollution and development

Many of England's lakes, rivers and estuaries are protected under the Conservation of Habits and Species Regulations (2017). These protected places are known as 'Habitats Sites'.

When a new housing development application is submitted, a competent body (usually the local authority or environmental agency) will carry out a Habitats Regulations Assessment (HRA) to assess the implications for that site. If damage due to nutrient pollution can't be ruled out, planning permission will be denied unless there are mitigation measures in place to reduce or eliminate the impact.

Nutrient neutrality 

Nutrient neutrality is a means of ensuring new residential developments do not increase the nutrient burden of nearby protected waters.

The concept emerged in 2019 when Natural England began advising local planning authorities with protected waters to only grant planning permission to new housing developments proven to be nutrient neutral.

According to Natural England:

"Development plans can be considered 'nutrient neutral' where they can demonstrate that they will cause no overall increase in nutrient pollution affecting specified Habitats Sites."

Nutrient neutrality is intended as an interim solution whilst Natural England works to restore Habitats Sites to favourable conditions.  

As a result, there is some doubt about how long nutrient neutrality rules will apply to developers.

Nutrient Mitigation Scheme

In July 2022, the UK Government announced the Nutrient Mitigation Scheme. Led by Natural England, the scheme was designed to reduce the impact of pollution in wastewater from new housing developments and support sustainable development.  

The legislation was welcomed by some as providing much needed protection for endangered habitats like the River Itchen in Hampshire.  But housing developers soon complained that it was putting unnecessary brakes on much needed building work.

In August 2023, the government published an amendment to the levelling up bill that if approved, would have meant planning authorities no longer had to consider nutrient neutrality as a material factor in planning applications.

However, this amendment failed in the Lords in September 2023.

For now, at least, developers will continue having to use mitigations to ensure any new development does not further contribute to the nutrient problem. Planning authorities will still have to consider nutrient neutrality as a material factor in planning applications.

The role of wastewater treatment in nutrient neutrality

Wastewater treatment can play a major role in the nutrient neutrality equation. Packaged wastewater plants by WCS Environmental Engineering (WCSEE) can remove up to 65% of the nutrients found in wastewater. These custom systems can be installed on both residential and commercial sites and treat wastewater flows from just one property up to a population of 30,000 people. They consume little energy and have few maintenance requirements. 

WCSEE is also developing further ways to remove nutrients without using chemicals, such as absorbent beads made from zeolite, a naturally occurring mineral that can safely remove phosphorus. In addition, they are trialling the use of ultraviolet light in treatment units to cultivate algae, which itself eliminates phosphorous and can be retained in the sludge produced for removal by the waste carrier.

Case study 

The developers of 23 high-end properties in Hampshire selected WCSEE technology to treat wastewater flows and ensure nutrient neutrality. The site's rural location close to the New Forest meant the discharge requirements were especially stringent.

WCSEE designed a custom onsite solution comprising a below-ground HiPAF sewage treatment plant and sand filter. The HiPAF sewage treatment plant has a 30% smaller footprint than comparable technologies. It also has the added benefit of a built-in timer for the blower(s), which halves the amount of energy used to treat effluent.

The sand filter is designed to remove excess suspended solids from the treated wastewater before it is discharged, bringing consent standards above what is normally expected from a biological process.

WCSEE worked closely with the developer's nutrient neutrality advisor to ensure the technology's nitrate removal capability was considered as part of the neutrality calculations submitted in the planning application. The solution offers the highest levels of environmental protection, and the developer's application was successful.

Summary

Nutrient pollution is a big problem with many implications for water quality. To be granted planning permission, developers need to ensure their projects will not increase nutrient pollution in nearby protected waters. Wastewater treatment technology can be used to ensure nutrient neutrality, preserve the environment, and help developers move forward with their plans. If you'd like to know more about how WCSEE can help with your project, please get in touch.