Independent analysis suggests Kerry sewage plant is affecting national park water quality

By Alastair Tibbs, The Kerryman

Analysis carried out on a river flowing into the county’s national park has indicated a nearby wastewater plant is affecting the water quality.

Environmental tests on Killarney Waste Water Treatment plant suggest the connected steam was by one metric, in the bottom one per cent of Irish rivers in the majority of samples.

Kerry Councillor John O’Donoghue had previously called for an independent assessment of the Killarney waste water treatment plant following concerns over the water quality in downstream ecosystems.

As part of an Environmental Protection Agency (EPA) report, the Folies steam, which passes the waste water plant before entering Lough Léin, was identified as the source of pollution in the downstream River Laune, though Uisce Éireann stated the plant was not at capacity.

However, new analysis conducted by Jean O’Dwyer, Head of Environment Science at Universtiy College Cork, suggests the plant is responsible for some of the pollutants.

Dr O’Dwyer found from 2024 EPA audit of the plant that measures linked to organic pollution were higher downstream of the plant than they were upstream, and were suggestive of waste water or agricultural influence.

Based on the European Environmental Agency (EEA) metrics, Biochemical Oxygen Demand (BOD), a key overall indicator of pollution, measured downstream of the plant put the Folies stream in the bottom one per cent Irish rivers, nine out of 11 times in 2024.

Measurements taken upstream showed that section of the river could be grouped comfortably with the majority of Irish rivers, in the best BOD class by EEA standards.

“Dissolved oxygen (DO) levels were also significantly different between upstream and downstream,” said Dr O’Dywer.

“Lower oxygen levels downstream would be consistent with organic influence from wastewater treatment effluent or from agriculture. Oxygen is essential for fish and aquatic insects, so reductions can stress ecological life.

“Higher levels of nutrients were also found downstream,” she continued, “when nutrients increase, they can encourage excessive plant and algae growth, which can further disrupt oxygen levels and overall river health.”

Dr O’Dywer did point out that ammonia and nitrate levels did not show significant changes between upstream and downstream, suggesting that the wastewater treatment process is effectively controlling these specific forms, or that these chemical species are quickly transformed within the river.

Uisce Eireann have replied that the plant was compliant with all emissions limits set out in its EPA discharge licence in 2024 and has had been found so far in 2025 to have been compliant with tests.

They added that the environmental monitoring of the River Folly shows that it is not meeting required environmental quality standards, both upstream and downstream of the plant.

“This indicates that the river is already of poor status due to other pressures on the receiving waters,” a spokesperson said.

“While some change in water quality indicators has been observed, it is not possible to attribute this directly to the wastewater treatment plant, as there are multiple potential contributing factors in the catchment including rainfall, runoff from roads, agriculture, private septic tank discharges, animal waste and leaks and spills etc.

“Importantly, the plant’s discharge is not considered to be having a measurable negative impact on the river under the EU Water Framework Directive.”