Detecting Wastewater Discharges and Assessing Ecological Risk in Real Time

How multivariate continuous monitoring enables proactive water quality management 

Wastewater discharges from engineered overflows, including combined sewer overflows (CSOs) and emergency bypasses, remain one of the most significant drivers of poor river health. Under Section 82 of the Environment Act, UK utilities are now required to provide continuous monitoring data and near real-time reporting of overflow events. 

While this transparency improves visibility, it leaves a major gap: what does the data actually mean for river health? Without ecological context, all events are treated the same, whether they cause significant environmental harm or have negligible impact. 

Most traditional systems are costly to install, maintain and often fail to capture the downstream ecological context, where environmental impacts occur. This limits utilities’ ability to prioritise response, inform the public accurately, and focus investment where it delivers the greatest benefit. 

To address this, AquaWatch has developed SWIM-OS, a data-driven approach using continuous, in-stream monitoring at paired upstream and downstream sites. Our Waqa5 sensors continuously measure five key water quality parameters, temperature, dissolved oxygen, turbidity, pH, and electrical conductivity, with optional ammonium sensing for higher-resolution detection. In many deployments, these are integrated with AI enabled camera modules that provide visual confirmation of discharge events and validate multivariate signatures in real time. 

By combining these field-based observations with advanced pattern recognition, SWIM-OS delivers near real-time ecological risk information, enabling utilities to move from reporting activity to managing outcomes. 

1. Capture - Continuous, Defensible Data 

At the core of AquaWatch’s approach is clean, reliable, and continuous data capture. Our WaQA5 in-stream sensors are deployed at paired upstream and downstream sites, forming the basis of defensible monitoring under frameworks like Section 82. 

• Measures five core parameters: temperature, dissolved oxygen, turbidity, pH, and electrical conductivity 

• Optional ammonium ISE sensor for higher-resolution detection 

• Optional high-frequency camera modules to provide visual confirmation of discharge events 

• Delivered as a fully managed Data-as-a-Service (DaaS) model where required, ensuring continuous calibration, servicing, QA/QC, and immediate swap out in case of hardware issues. 

  
  

By ensuring the capture layer is reliable, AquaWatch ensures the integrity of the inputs, enabling high-confidence detection and reporting. 

WaQA, the AquaWatch floating sensor array, deployed at a Watercare discharge point

2. Analyse - Detecting Discharges in Real Time 

Captured data flows directly into SIWM-OS's multivariate detection model, which identifies characteristic patterns associated with wastewater discharges. 

• Uses paired-site comparisons to distinguish wastewater impacts from natural processes 

• Detects departures from diel cycles and hydrological responses that single-parameter thresholds often miss 

• Ammonium readings are sense-checked in real time against other parameters and site context for defensibility 

This integration of capture and analysis improves detection specificity, reduces false positives, and strengthens regulatory confidence. 

3. Act - Prioritising Ecological Risk 

Once a potential discharge is detected, SWIM-OS automatically calculates its ecological risk AquaScore based on: 

• Event duration, how long the discharge persists 

• Magnitude of exceedance, how far observed conditions stray beyond thresholds 

• Contextual baselines, using site-specific data alongside guideline values 

Because detection is continuous and integrated with real-time capture, we can deliver near real-time ecological risk reviews, enabling operators and regulators to: 

• Prioritise high-risk events over lower-impact anomalies 

• Respond rapidly to protect sensitive ecosystems 

• Meet reporting requirements with credible, contextualised insights 

AquaScore - Calculated through SWIM-OS

4. Improve - Driving Long-Term Outcomes 

Beyond immediate detection and response, AquaWatch generates insights that inform broader catchment management strategies and investment planning: 

• Identify recurring overflow patterns to target infrastructure upgrades 

• Provide transparent, defensible reporting for regulators and the public 

• Build stakeholder trust with contextualised ecological impact data 

• Align operational monitoring with evolving policy priorities focused on river health 

  

  SWIM-OS tracking of change, post mitigations

Results from Field Applications 

Across multiple test sites, this method successfully identified wastewater discharges in real time and distinguished them from other disturbances such as rainfall-driven turbidity spikes. 

Key findings: 

• Multivariate signatures outperformed single-parameter thresholds, especially under variable flow conditions. 

• Integration of ammonium readings improved detection confidence when sense-checked in real time. 

• Near real-time ecological risk reviews enabled faster prioritisation of high-impact events. 

• Insights supported both operational response and long-term planning.