With a nutrient neutral approach to new property developments expected to become more widespread across England, increasing numbers of developers are giving closer consideration to wastewater treatment, writes Andrew Baird, technical director at water recycling specialist WPL.

Nutrient neutral planning requirements put in place in parts of England to protect sensitive waters and marine life continues to pose a conundrum for many property developers. The concept of nutrient neutrality emerged in June 2019, when government advisor Natural England began issuing advice to local authorities with protected waters to only grant planning permission to new property developments proven to be nutrient neutral.

The guidance applies to areas with surface waters that are impacted by high levels of the contaminants, primarily phosphate and nitrate, which are present in treated wastewater that is discharged to watercourses in the final stage of the recycling process.  The contaminants, often referred to as nutrients, can lead to increased growth of algae, which can have a detrimental impact on water environments and ecosystems – a process known as eutrophication.

Nutrient neutrality is a means of ensuring new developments used for housing, mixed-use and tourism do not increase the nutrient burden of nearby protected waters. In the affected regions, developers must prove their schemes would be neutral by demonstrating in planning applications how they would remove or offset the full amount of nutrients anticipated.

For properties that are not on mains drainage, onsite wastewater treatment can be a significant part of the neutrality equation. As such, sustainable water recycling specialist WPL continues to see an increase in enquiries about its packaged wastewater treatment plants, which can remove up to 65% of nutrients found in wastewater.  By comparison, the installation of a septic tank would have no positive impact on levels.

Packaged plants are pre-manufactured, custom systems that can be installed on most commercial and residential sites and can treat wastewater flows from just one property, up to a population of 30,000 people. WPL’s patented technology is fully compliant with Environment Agency regulations, which means final effluent can be safely discharged to a soakaway or watercourse.

Images: WPL HiPAF® below the ground units and Modular Hybrid-SAF™ above the ground units

The modular units can be installed in a tight footprint and once they are up-and-running, visual impact, energy consumption and maintenance requirements are low. WPL can provide documentation confirming the effectiveness of its equipment, which can be submitted with a planning application. Importantly, the process uses no chemicals, which is kinder to the environment and is far safer, particularly in a domestic environment. However, while onsite treatment is effective in removing a significant amount, developers must accept that there is no technology suitable for domestic use that would remove 100% of containments.  Nutrient neutrality can only be achieved through a combination of measures and in most cases offsetting – removing nutrients elsewhere in the catchment – will have to be considered, which local planners can advise on.

The issue of nutrient neutrality is not going to go away – while Natural England’s initial guidance focused on several planning authorities in Hampshire, it now applies to selected authorities in Kent and Somerset, with more expected.

With the environment at the heart of WPL’s operations, its research and development team, with support from Portsmouth University, is looking at further low-impact ways to remove more than 65% of nutrients. Our aim is to reduce levels for our utility, commercial and domestic customers, without the use of chemicals.

Technology being researched includes absorbent beads made from Zeolite, a natural occurring mineral which will safely remove phosphorous. Elsewhere, we are trialing the use of ultraviolet light in treatment units to create a suitable environment for the growth of algae, which itself removes phosphorous, and can be retained in the sludge produced for removal by the waste carrier. We are also working on solutions to support water companies with their own large-scale, stringent targets for nutrient removal.

While the issue is complex and the guidance under constant review, some effective mitigation schemes have taken place to the benefit and relief of developers, and we are confident of technological advancements emerging soon.

Developers should read Natural England’s guidance carefully, seek professional advice and of course contact WPL for clear technical advice.