Belfast Lough: Environment watchdog to investigate sewage discharges
November 25, 2025
Environment watchdog to investigate three bodies over sewage
Getty ImagesTwo Stormont departments are among three bodies under investigation by the UK’s environment watchdog over sewage discharges into Belfast Lough.
The investigation by the Office for Environmental Protection (OEP) will examine how the Utility Regulator, the Department for Infrastructure (DfI) and the Department of Agriculture, Environment and Rural Affairs (Daera) regulate sewage discharges by NI Water.
The OEP’s chief executive Natalie Prosser said nature was “under unsustainable pressure” and these bodies were “the primary regulators” for water quality.
Daera Minister Andrew Muir said the investigation was “sadly not unexpected”, and DfI welcomed it.
PA Media‘A complex problem’
Drainage in Belfast was designed by Victorian engineers as a combined system, where storm water and sewage use the same pipes.
Officials have previously warned of the threat sewage spills pose to the ecosystem of Belfast Lough.
“This is a complex problem with no quick fixes,” said Ms Prosser.
“But our investigation will contribute to the work already underway in this area, so government and other decision-makers can be targeted and effective in driving much-needed improvements in water quality.”
The focus of the investigation will be the regulation of how untreated wastewater, including raw sewage, is discharged into Belfast Lough and its surrounding rivers from Wastewater Treatment Works (WWTW) and Combined Sewer Overflows (CSOs).
WWTWs treat wastewater from homes and businesses to make it safe to be returned to the environment.
That includes treating raw sewage.
During heavy rainfall, when sewer capacity may be exceeded, meaning there is a risk of sewage backing up into homes, streets and businesses, CSOs operate as a safety valve to prevent flooding.

Bigger than Belfast
The OEP previously found Northern Ireland may have breached laws designed to protect water quality by not implementing them as they should have.
Ms Prosser said the OEP is aware that wastewater and sewage issues exist in other rivers and lakes.
“Our interest is in driving improvement across the wider regulatory system.
“What we find in this investigation will be relevant across Northern Ireland.”
Getty ImagesNI Water not included
Sewage and water services in Northern Ireland are provided by NI Water.
It is not in the scope of this investigation because, Ms Prosser said, it is not the OEP’s role to “step into the shoes of the regulators” but to ensure they are fulfilling their legal duties.
They “play key roles in enforcing NI Water’s own responsibilities” in relation to sewage discharges.
However, she said the watchdog would be speaking to NI Water as part of the investigation.
Ms Prosser said: “We’ll be looking at whether the Utility Regulator and DfI have met their duties to take necessary enforcement action, where Northern Ireland Water may not be fulfilling their own responsibilities for sewage discharges.
“For Daera, we’ll examine whether it has set and updated the conditions that allow sewage overflows to spill in line with legal standards.”
Under a protection known as SORPI, NI Water is not fined in the same way that water companies in Great Britain are for sewage pollution incidents.
A review of environmental governance in Northern Ireland recommended that should change.
Causes of water pollution
In a previous report on the causes of nature loss in Northern Ireland, the OEP confirmed that, along with agriculture, wastewater was one of the biggest contributors to water pollution.
That pollution includes excess nutrients from fertilisers, animal waste coming from imported animal feeds and sewage.
Excess nutrients are a major cause of the blue green algal crisis in Lough Neagh and elsewhere for the past three summers.
If the OEP finds there has been any failure to comply with environmental law, it will work with the authorities involved but can take court action if there is no agreement.
Search
RECENT PRESS RELEASES
Related Post
