The number of registered domestic waste water treatment systems increased by 0.9% in 2020 to 475,990. There was an increase in every local authority in 2020 with Donegal recording the highest annual increase of 1.2% (see Figure 1 and Table 1).
In 2020 Cork had the highest proportion of domestic waste water treatment systems at 11.4% followed by Galway (8.8%), Kerry (7.1%), Donegal (6.4%), Mayo (6.1%), Tipperary (5.5%) and Wexford (5.3%). These seven counties accounted for 50.6% of all individual waste water treatment systems (see Table A and Figure 2).
Cork accounted for 14.3% of all new registrations in 2020 followed by Donegal at 8.9% (see Table 2).
Household owners accounted for 97.1% of all registered waste water treatment systems in 2020. Public authorities accounted for 1.5% and Other non-domestic owners accounted for the remaining 1.4% (see Table 3). In Longford public authorities accounted for 4.3% of all owners in 2020 whereas in Kildare they only accounted for 0.1%.
https://www.cso.ie/en/releasesandpublications/er/dwwts/domesticwastewatertreatmentsystems2020/