Sewage sludge 'moved across Northern Ireland'
Lorry loads of waste water are being taken to treatment sites across NI because the sewage sludge incinerator in Belfast is out of commission.
Residents near a treatment plant in Limavady have complained about the smell which they say has been caused by the increased capacity at the site.
The Belfast incinerator is run by a private contractor.
It is expected to reopen at the end of June after being upgraded.
Friends of the Earth said they believe there are better ways of treating sewage.
Spokesperson Declan Allison said: "Incineration of sewage sludge is in itself a bit of a problem.
"There are other ways, better ways I would argue, of treating sewage."