Sewage Sludge and Biosolids

The treatment of the wastewater generated in greater Dublin by homes, schools, businesses and industry produces wastewater sludge.

Wastewater sludge is made up mainly of organic matter that has been removed from the wastewater during the treatment process. Further treatment of this sludge is required to enable its safe and efficient re‐use or disposal.

The further processing of the sludge results in ‘biosolids’. Biosolids are a biologically stable product free of harmful pathogens (viruses, bacteria etc.) and containing high levels of plant nutrients (nitrogen, phosphorus etc.). The treatment of sludge happens at the wastewater treatment plant.

Biosolids are then transported to a biosolids storage facility prior to being outputted for use in agriculture and forestry.

Most of the biosolids produced in Ireland (98%) are currently reused on agricultural lands as a soil conditioner and as a replacement for chemical fertilisers.

The use of biosolids on agriculture lands is strictly regulated under European and National law.

One of the conditions of use is a strict prohibition on spreading biosolids on land over the winter period (October to January).

This restriction means that biosolids reused in agriculture need to be stored for certain periods over each calendar year.

Note from 5th Nitrates Action Plan on Sewage/Industrial Sludges


The use of sewage sludge is managed by Irish Water through its National Wastewater Sludge Management Plan.

The application of sewage sludge to agricultural land is controlled by local authorities through the maintenance of sludge registers and inspection/enforcement programmes.

The EPA regulates industries (including dairy processing and animal slaughtering) that generate industrial sludges through IED licences.

The application of industrial sludges as an organic fertiliser to agricultural land is controlled under the Good Agricultural Practice regulations.

However currently there is not an integrated approach or data system available that identifies the loads and spreadlands where sludges are applied.

A comprehensive understanding of the movement of sludges and the application of sludges to agricultural land is required to ensure the existing controls are fit for purpose.


A review of the management and oversight of sludges being applied to land will be carried out by a working group established under the National Technical Implementation Group (NTIG), which is part of the River Basin Management Planning and Water Framework Directive governance structures.

Recommendations arising will be brought back to the WFD governance structures for consideration.

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