Cork sewerage treatment systems under pressure due 'shock loading' of milk

“The environmental impact of one litre of milk is equivalent to a full day’s wastewater from a family household,” said Uisce Éireann's head of wastewater treatment control, Paddy O'Dwyer.

Uisce Éireann, formerly known as Irish Water, said a number of such cases of the dumping of large quantities of milk have occurred in several parts of the county.

Uisce Éireann (UE) has warned that sewerage treatment systems may be seriously impacted if there is a repeat of large quantities of milk being dumped into drains in Co Cork.

The utility, formerly known as Irish Water, issued the warning after experiencing a number of such cases that have occurred in several parts of the county.

Paddy O’Dwyer, the company’s head of wastewater treatment control, said last spring that the treatment plant serving the Aghabullogue area “received a shock loading of milk" — which refers to very high quantities in a short burst.

He said this put significant pressure on the wastewater treatment plant, resulting in operational difficulties with the treatment process.

“We have also had similar issues in Grenagh, Rylane, Kilbrittain, and Dripsey, so it has proved both challenging and costly,” said Mr O’Dwyer.

The reason for the dumping of large quantities of milk in these areas is unclear, but Mr O’Dwyer said they are serious because the presence of milk saps the oxygen needed by bacteria and other microorganisms to break down effluent.

When large quantities of milk cannot be broken down by the microorganisms, they go through the system untreated and therefore ultimately end up in rivers and can have a major impact on the local environment.

“The environmental impact of one litre of milk is equivalent to a full day’s wastewater from a family household,” said Mr O'Dwyer.

"Last year we issued an appeal to all parties in the milk industry, and have seen some improvement. It’s particularly common during the spring and summer months, and it puts a significant strain on Uisce Éireann’s wastewater infrastructure. 

We are not talking about pouring a litre or two of milk from the fridge out, this is large quantities of milk that need to be disposed of appropriately."

The Environmental Protection Agency (EPA) said that while it is not a systemic issue across the country, it supports UE's message.

However, Cork Environmental Forum (CEF) said it warrants a "thorough investigation", given that a number of places in Cork reported such surges.

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CEF co-ordinator Bernie Connolly said: “The issue of large quantities of milk being disposed into the wastewater treatment system is unusual and highly perturbing. 

"Given that this is not a one-off, with a number of such reported incidents in the mid-Cork area as well as North Cork and West Cork, we would hope that the issue is thoroughly investigated by Uisce Éireann and State bodies to ascertain the reasons for such disposal, and to prevent any such future incidents."

The sector already has a hugely negative impact on water quality, and the added harm of milk disposed of incorrectly will exacerbate further declines, she added.

The Department of Housing said it is a matter for UE.

A spokesperson said the department is currently preparing the third River Basin Management Plan for Ireland up to 2027. 

The plan will "describe the main pressures and activities affecting water status, set out the environmental objectives to be achieved up to 2027, and identify the measures needed to achieve these objectives, including those highlighted by the EPA", the spokesperson added.