Guidance

Using wetlands to improve treated effluent discharge: RPS 260

Published 29 November 2022

Applies to England

Water and sewerage companies (WaSCs) cannot use this regulatory position statement (RPS). It sets out the Environment Agency’s enforcement position for nutrient treatment wetlands (NTWs) operated by parties other than WaSCs. The NTW must provide additional treatment to improve the final effluent quality discharged from a WaSC wastewater treatment works (WwTW). This treatment must not result in the final effluent quality deteriorating.

You must notify the Environment Agency by email if you want to use this RPS. Provide the 6-figure National Grid Reference for the discharge point from your NTW.

Email WETprogramme@environment-agency.gov.uk

NTWs are a subset of integrated constructed wetlands for treating nutrients, such as phosphate and nitrogen.

This RPS does not change your legal requirement to hold an environmental permit for a waste operation to operate a NTW.

However, the Environment Agency will not normally take enforcement action against you if do not hold a permit, provided:

• your activity meets the description set out in this RPS
• you comply with the conditions set out in this RPS
• your activity does not cause (and is not likely to cause) pollution of the environment or harm to human health

WaSCs discharging into third party NTWs have a duty of care to transfer waste to an authorised person. This RPS does not change this legal obligation. However, the Environment Agency will not normally take enforcement action against WaSCs if the operator of the NTW receiving their wastewater discharge has notified the Environment Agency that they are using this RPS.

This RPS does not apply to any other legal requirements.

When this RPS applies

This RPS is for surface flow NTWs with submerged and emergent vegetation where all the following apply:

• they provide further treatment to treated final effluent that has been discharged directly into the NTW from a WaSC WwTW
• the discharge from the WwTW is authorised by an environmental permit
• the NTW is not operated by, or on behalf of, a WaSC

Conditions you must comply with

Design and maintenance of your NTW

Your NTW must:

• improve the quality of the final effluent received from the WaSC’s WwTW
• provide hydraulic efficiency and effective treatment, avoiding preferential flow paths and ‘dead areas’ with limited throughflow
• follow Natural England’s Wetland Mitigation Framework- Framework Approach for Responding to Wetland Mitigation Proposals, if your NTW is to achieve nutrient neutrality
• be planted with a range of native submerged or emergent aquatic plants (or both) and you must manage these to maintain a healthy plant population
• be managed and maintained over its design life and you must make sure you continue to meet these design and construction requirements

Protecting surface water and groundwater

You must also take all necessary measures to make sure groundwater is protected.

You must make sure the NTW:

• is not in hydraulic continuity with the local groundwater
• does not cause a deterioration in the quality of the receiving surface water or groundwater

You must have a written, agreed procedure with the WaSC. It must include procedures for communicating effectively on treatment, performance or operational incidents at either the WwTW or NTW that could result in harm to the environment. In the event of an environmental incident, the Environment Agency must be notified in line with the procedures agreed between you and the WaSC.

You must construct the base of your NTW with either a soil or a synthetic liner. The liner must meet these permeability requirements:

• the base of your NTW must have a low permeability, equivalent to or lower than 1x10^-7 metres per second, so that effluent does not infiltrate downwards into underlying groundwater at an unacceptable rate
• permeability testing must meet the standards in BS1377-6:1990 or to BS EN 1997-2:2007 and you must have analysis by a United Kingdom Accreditation Standard (UKAS) laboratory accredited for the test – a civil engineer must confirm that you have placed the soil liner to the required permeability
• if you use a synthetic liner it must have the equivalent permeability to the soil liner

Making sure your NTW does not impact conservation sites

You must make sure construction of, and discharge from, the NTW does not cause:

• adverse effects to a designated conservation site or features
• damage to protected species or habitats

Conservation sites include:

• European sites (Special Areas of Conservation and Special Protection Areas)
• Ramsar sites
• Sites of Special Scientific Interest
• national and local nature reserves

Monitoring your NTW

You must monitor the following water quality parameters in the effluent entering and leaving the NTW:

• ATU-BOD as O₂ (the biochemical oxygen demand, measured after 5 days at 20⁰C with nitrification suppressed by the addition of allylthiourea) measured in milligrams per litre (mg/l)
• ammoniacal nitrogen expressed as N measured in mg/l
• suspended solids measured after drying at 105°C measured in mg/l
• total phosphorus as P measured in mg/l
• total nitrogen expressed as N in mg/l
• nitrate expressed as N measured in mg/l

You must also take and analyse at least one spot sample a month of both the effluent entering and leaving the NTW. You must use a UKAS laboratory accredited for the tests to analyse the samples.

Decommissioning

You must have a decommissioning plan for your NTW, as described in Natural England’s Wetland Mitigation Framework.

Keep records

You must keep records to show you have complied with this RPS from when you start using it until 2 years after you finish using it. You must make these records available to the Environment Agency on request.

When you must check back

The Environment Agency will review this RPS by 31 August 2024. You will need to check back then to see if it still applies or if you need to apply for an environmental permit or take appropriate alternative action.

The Environment Agency can withdraw or amend this enforcement position before it expires if they consider it necessary. This includes where the activity that this RPS relates to has not changed.

If you cannot comply with this RPS

If you operate under this RPS but think you may no longer be able to comply with it, you must tell the Environment Agency immediately.

Email WETProgramme@environment-agency.gov.uk

Contact the Environment Agency

Email WETProgramme@environment-agency.gov.uk