Combining sewer and surface water insights across Northern Ireland Water's wastewater network

The problem

Previsico, in partnership with UDlive, have successfully delivered to Northern Ireland Water an AI-informed sewage network prediction software solution.

More extreme weather, growing populations, increased development, ageing infrastructure, and a hardening regulatory environment are all putting significant pressure on water companies to find ways to manage their sewer network and prevent overflows. One of the principal challenges faced by wastewater companies like Northern Ireland Water is that sewage treatment works have limited capacity to process incoming sewage water. Too much or too little sewage unbalances the treatment process. Excess sewage is therefore usually diverted into storage tanks and then spilled into the environment if capacity is exceeded. In November 2021, the Environment Agency announced it would urgently investigate 2,480 sewage treatment catchments and prosecute water companies and their directors for pollution arising from wastewater networks.

However, the sewer network itself offers a large capacity for balancing the network and avoiding catchment-level overflows. This network balancing is necessary in all conditions, and having a proactive, predictive approach is key to ensuring sewage can be optimally distributed and processed, minimising environmental impacts from storm conditions. In the UK, private investment in storm overflow improvements alone is estimated by DEFRA to be £3.5 billion between 2020 and 2025.

Benefits

The project has further provided Northern Ireland Water with the means to monitor difficult and dangerous CSOs, better monitor the nature of effluent from traders discharging into their network, and the tools (event duration monitors, EDMs) to accurately characterise spills and detect blockages.

The project delivered benefits to NI Water in the following ways:

• Delivered at scale and speed working hand-in-hand with water companies.
• Insights into causes and sources of risk.
• Insights identify the most vulnerable areas, including those susceptible to blockage and infiltration.
• Situational understanding of asset performance through replay and prediction, and of capacity at the catchment scale.
• Understanding of combined sewers' interaction with foul sewers with known concerns.
• Areas of most and least concern, OT calibration feedback and asset configuration.
• Support for better allocation of often limited resources and, therefore, value for the bill-payer.
• Support for generation of capacity and so a reduction of spills, with a variety of environmental and socio-economic benefits.
• Novel workflow supporting efficient instrumentation and/or simple maintenance fixes using a cost/benefit approach.

The results

Over two phases of the project, 102 locations were identified, with approximately 85% of the highlighted locations yielding "finds", defined as defects detected upon inspection or through instrumentation. Importantly, finds identified rapidly and at broad spatial scales support Northern Ireland Water in being able to optimise and then deliver solutions (including capital schemes) on a cost-benefit basis. Defects identified during the two phases of this project include but are not limited to:

• Instances of clean water leakage, reducing network capacity by approximately 86m³ per day.
• Instances of surface water infiltration, reducing network capacity by circa 86m³ per day.
• Tidal inflow, identified at multiple sites.

These identified defects can be resolved in a variety of ways, ranging from small maintenance tasks (blockage clearance, replacing a cracked chamber lid) to significant civil engineering projects (building a new pipe or treatment works).