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Sewerage is defined as waste water and excrement conveyed in sewers, and is a cause for concern due to its contribution to the proliferation of algal blooms in bodies of water , and due to the health risks it poses to the environment and humans. Untreated sewerage is a waste product that also contains a host of harmful bacteria that can be severely detrimental to human and environmental health. Bugs like Escherichia coli (bacterium commonly found in the lower intestine of warm-blooded organisms) can enter the water column and be taken up by commercially farmed (and wild) shellfish. Any shellfish which exhibit unsafe levels of E.coli in their tissues, are deemed unfit for human consumption and cannot be sold. This can impact on commercial companies with some Irish seasonal markets being affected significantly in July 2015 (EPA, 2015).


Figure 1: Escherichia coli (Rocky Mountain Laboratories) (WWW2)

In 2015, the EPA reported that raw sewerage was being discharged into 45 rivers, lakes and coastal areas around the state, leading to poor quality water which could pose a risk to human health and the aquatic environment. Some discharged bodies of water had received preliminary treatment which entails “a basic form of treatment typically designed to remove floating debris, oils, fats, grease, grit, rags and large solids from the raw waste water” (Gleeson 2015), however raw, untreated waste was being deposited directly into waterways which has been linked to the poor quality of water at a number of bathing sites across the Irish coastline.


Management Options for Domestic Waste Water (WWW3)

The Irish Independent reported in 2015 that an independent monitoring of 263 treatment plants established that 71 failed to comply with effluent quality standards stipulated in their licences. Moves are being made to tackle this issue with additional water treatment facilities scheduled for completion by the end of 2016. Since the publication of the EPA report, two additional treatment facilities have been built at locations that failed to comply with treatment regulations, however 12 areas have currently failed to meet their deadline for improvements which has lead to further pressures from the EU Commission (O’Brien 2016).

Despite these shortfalls, records show that nitrate levels have decreased by almost 19% and phosphate levels by close to 38% recently, which is a good sign for Irish coastal waters. Due to the WFD and work carried out by the Department for the Environment, sewage treatment and disposal has come on greatly with 67.4% of Irish coastal waters presenting as “moderate to good” quality, in terms of ecological health.

To learn more about water quality you can visit the Environmental Protection Agency website where you will find useful infographics on environmental issues such as domestic waste water management or national bathing water quality. You can also review the quality of bathing waters in your area by exploring this SPLASH interactive map.

Seán & Orla-Peach


Environmental Protection Agency (1995) EPA Wastewater Treatment Manual: Preliminary Treatment.

Environmental Protection Agency (2015) Water Quality in Ireland 2010 – 2012.

Gleeson, C. (2015) EPA Report Highlights Raw Sewage Discharge at 45 Sites. the Irish Times.

Mostofa, K. M. G., Liu, C. Q., Vione, D., Gao, K., & Ogawa, H. (2013). Sources, factors, mechanisms and possible solutions to pollutants in marine ecosystems. Environmental Pollution, 182, 461–478.

O’Brien, T. (2016) EU Takes Action Over Sewage Pollution in State’s Waterways. The Irish times.

WWW1 – Sewerage Treatment Plant

WWW2 – Rocky Mountain Laboratories: E. Coli

WWW3 – Management Options for Domestic Waste Water