EPA orders Irish Water to stop sludge discharge into River Blackwater from Mallow plant

EPA inspectors had found “highly coloured” water being discharged into the Blackwater from the sludge-holding tank at the Mallow plant

The EPA told Irish Water to implement an action programme to improve the sludge-handling facilities at the Mallow plant and to liaise with Inland Fisheries Ireland and the National Parks and Wildlife Service to ensure any discharge was not having a negative impact on the River Blackwater. File picture: Denis Scannell

Irish Water has been ordered by the State’s environmental watchdog to immediately cease the discharge of sludge into the River Blackwater following an inspection of the wastewater treatment plant in Mallow, Co. Cork.

An audit of the drinking water supply in Mallow by officials from the Environmental Protection Agency in August found sludge arising from the treatment process at the plant was not being adequately managed.

EPA inspectors noted “highly coloured” water was being discharged into the Blackwater from the sludge-holding tank at the Mallow plant on the day of the audit.

They concluded that the existing sludge treatment infrastructure at the plant was providing insufficient sludge settlement which resulted in sludge being discharged into the river.

The audit on the Mallow supply was carried out to assess the performance of Irish Water in providing clean and wholesome water to the public in the treatment plant’s catchment area.

It arose from Irish Water notifying the EPA that a member of the public had complained about a discharge into the River Blackwater from the plant. The facility located at the eastern end of Mallow at Ballyellis provides an average of 2,400 cubic metres of drinking water daily to a population of 5,000 people.

The company informed the EPA that its own investigation had concluded that there was nothing unusual in the day-to-day process at the plant around the time that the complaint had been made.

Irish Water explained that the outflow of water used in cleaning or industrial use had been an issue in the past and a previous cause of a complaint, particularly at times of low water levels in the river.

The EPA noted that the complainant had not been contacted with an update on the outcome of the Irish Water investigation and the proposed remedial actions. It also found there was no continuous monitoring of the turbidity of liquid in the sludge-holding tank or of the discharge into the River Blackwater.

Interim works

Irish Water and Cork County Council notified the EPA that interim remedial works were planned to include the desludging of the sludge-holding tank as well as measures to increase solid retention in the tank.

They also said the frequency of removing sludge from the holding tank would be increased to twice a month until the interim works were completed. Records indicate that sludge was previously only removed and transported to a treatment plant in Limerick once every two or three months.

Irish Water said it was also examining longer-term remedial measures including connecting the sludge-holding tank to a foul sewer. The company said such a proposal had first been raised in 2018 but it had not been progressed at the time.

The EPA said Irish Water needed to ensure that its existing methods of handling and disposing of sludge at the Mallow plant were not in contravention of the Waste Management Act. During the inspection of the plant, EPA inspectors also found that the depth of filters were below the recommended minimum depth.

The EPA told Irish Water to implement an action programme to improve the sludge-handling facilities at the Mallow plant and to liaise with Inland Fisheries Ireland and the National Parks and Wildlife Service to ensure any discharge was not having a negative impact on the River Blackwater.

It said the company should also liaise with the council to determine if it needed a discharge licence for material released from the sludge-holding tank into the river.