The urban waste water treatment directive sets treatment standards that waste water treatment plant discharges must meet. The EPA issues licenses that are more detailed and may specify stricter/additional treatment standards where needed on a site-specific basis to protect the local environment. Licenses may also require infrastructural changes such as relocation of discharges to larger water bodies with more capacity to take the treated discharges.
42% of Irish Water’s treatment plants met licence discharge requirements in 2021.
Excessive amounts of nutrients such as ortho-phosphate can cause pollution in rivers and lakes. The EPA sets standards in our licences for the amount of ortho-phosphate that may be released into the water environment. If effluent doesn’t meet these standards it may lead to excessive and unwanted growth of algae and aquatic plants.
The graph below shows the percentage of Irish Water's treatment plants that complied with the ortho-phosphate standards in their licences. Almost two thirds (64%) of treatment plants met the standards in 2021, similar to 2020.
Biochemical Oxygen Demand (BOD) is one of the key parameters to assess the polluting potential of waste water. BOD measures the amount of oxygen used up (demanded) to break down and get rid of polluting matter in the effluent. The EPA sets standards in our licences for BOD that may be released into the water environment. If effluent doesn’t meet these standards it may lead to a drop in the oxygen levels in the receiving waters, which could harm aquatic life and biodiversity.
The graph below shows the percentage of Irish Water's treatment plants that complied with the BOD standards in their licences. Over three quarters (77%) of treatment plants met the standards in 2021.