Untreated sewage discharges or even primary treatment pose a real risk to bather health. Many combined storm outfalls (CSOs) are unmarked and may trigger with no notification until sanitary debris is seen in the water. If this happens then bathers should get out of the water immediately and notify the relevant local authority and the EPA.
Over 94% of Ireland’s waste water received at least secondary biological treatment which significantly reduces the risk of pollution by organic matter and the numbers of bacteria in the sewage. Several wastewater treatment plants also have ultra-violet (UV) disinfection facilities at the end-of-pipe to reduce numbers of bacteria even further. However, where there are untreated discharges or even primary treatment (settlement of solids before discharging), the numbers of bacteria and other organisms such as viruses or parasites can pose a real risk to bather health.
Following a review of over 1,000 urban areas subject to the waste water discharge authorisation programme, 43 locations were identified where waste water was still being discharged without treatment at the end of 2015. Over 80% of these areas discharge to estuarine or coastal waters which include some popular locations close to beaches such as Arklow, Gorey / Courtown, Lahinch and Bundoran. These beaches, thankfully, do not appear to be being affected by sewage discharges but the possibility of accidental pollution is very real. Irish Water has provided a timeframe for the provision of infrastructure to eliminate the discharge of untreated waste water from these areas but it is likely to be at least 2022 before all of these areas have been addressed.
There are three types of sewer systems: wastewater only, storm water only and combined (mixed). Combined sewer systems collect domestic and industrial wastewater, as well as storm water together in one pipe. The purpose of combined sewer systems is to transport this combination of sewage and rainwater to a wastewater treatment plant for processing. Even with suitable wastewater treatment facilities there can often be situations where rainfall is so heavy that any storm water retention tanks can fill within a few hours and there is a need for CSOs to be in place to act as a pressure relief valve when the sewers are hydraulically too full.