Emerging Pollutants: A potential challenge for continuous water quality monitoring

Emerging Pollutants (EPs) refer to a wide range of synthetic or naturally occurring chemicals and compounds that have recently been identified as potentially harmful to aquatic ecosystems and human health. These substances were not previously considered in routine water quality monitoring programs due to limited knowledge or inadequate detection methods.

Section 82 of the 2021 Environment Act has for the first time imposed a requirement on Water and Sewage Companies (WaSCs) to continuously monitor the quality of receiving water upstream and downstream of their assets. The intention is to allow WaSCs to assess the impact of discharges from their assets on the receiving watercourse and ultimately address any harm caused by these, in line with Storm Overflow Discharge Reduction Plan targets.

Provisional technical guidance has been provided by Defra which outlines a framework for the objectives, scope, monitoring requirements and timelines. Whilst final standards are yet to be ratified, the current requirements are to monitor the following parameters:

  • Dissolved oxygen
  • Temperature and pH
  • Turbidity
  • Ammonia

Future challenges

Timelines for the installation and maintenance of monitoring equipment across all CSOs discharging to watercourses are onerous, given that long-term continuous monitoring of water quality parameters on the scale proposed is unprecedented. WaSCs must begin roll out no later than 2025 with the full list of statutory assets being continuously monitored by 2035.

More importantly, 40% of sites including all high priority sites must have monitoring by 2030, including any assets which discharge to:

  • Sites of Special Scientific Interest (SSSIs)
  • Special Areas of Conservation (SACs)
  • Urban Wastewater Treatment Regulations sensitive areas
  • Chalk streams
  • Any assets within 5km upstream of designated inland or estuarine bathing waters
  • Waters currently failing WFD ecological standards due to storm overflows or final effluent

This gives WaSCs just under seven years to roll out thousands of monitors and much research is still necessary to understand the best kinds of monitors and testing equipment for use in-situ. With many requirements still to be established following public consultation, WaSCs are understandably concerned. Management of a suddenly increasing asset base and a huge influx of data which needs to be analysed and cross referenced against EDM data, and made publicly available in near real-time, will require a significant mobilisation of resources and rapid upskilling of operators in the industry.

Understanding Emerging Pollutants (EPs)

Something that is currently being overlooked in this rapid mobilisation is the impact of Emerging Pollutants (EPs) contained within both raw sewage effluent discharges from CSOs, and to a lesser extent, in continuously discharging treated sewer effluent from WwTWs. According to UNESCO, “Emerging pollutants can be understood in a broad sense as any synthetic or naturally-occurring chemical or any microorganism that is not commonly monitored or regulated in the environment with potentially known or suspected adverse ecological and human health effects.”

The main pollutants of concern fall into three categories:

  • Organic compounds such as pharmaceuticals, in particular endocrine disrupting chemicals present in hormonal treatments such as birth control, and NSAIDs such as ibuprofen and Diclofenac
  • Inorganic compounds such as heavy metals
  • Particulates such as micro and nanoplastics

Many emerging pollutants are not currently well understood and their effects on human health and our environment are potentially wide ranging. Furthermore, current research indicates that traditional water treatment processes are not 100% effective at removing them, with emerging treatment technologies yet to show effectiveness at removing these compounds fully.

Some major concerns are endocrine disruption, including feminisation and sexual organ development disruption in frogs and fish, potential contamination of water supply for humans which could lead to exposure to chemicals with toxic effects such as neurotoxicity and carcinogenicity, as well as the potential to contribute to the development of antibiotic resistant bacteria. Studies have shown that CSO discharges are an important source of emerging pollutants, and the contributions from CSOs alone can cause concentrations of some compounds to exceed no-effect thresholds in the environment (See article; Chèvre, et al., 2013).

The need for continuous Water Quality Monitoring

As we begin to accelerate progress on controlling and reducing the impacts of currently well understood pollutants, the focus of efforts in water quality monitoring could shift towards these emerging pollutants as the effects become better understood. It should be noted that the 2021 Environment Act allows for the Secretary of State for the Environment, Food and Rural Affairs to add any pollutant or monitoring parameter to the list of parameters WaSCs must continuously monitor, through regulations.

Many of these compounds are already on the WFD “watch-list” and it is not unreasonable to assume that, as public awareness of some of these compounds and their effects increases, the water industry might have to suddenly shift its focus towards controlling them. As we have already seen with the rapid rise in awareness of intermittent discharges, the water industry needs to be agile and ready to adapt.

RPS is currently restructuring our wastewater offering, closer integrating our Operations and Services businesses. This is allowing us to better support our clients in the rollout of monitoring and realise the benefits of having these monitors installed. Using Waternet we can also provide support for hosting, visualising and analysing WQ monitoring data alongside EDM and sewer operational data.


Water is vital to human life, health, and prosperity. Managing it is one of the most complex issues that faces our world today. We work alongside world-renowned water custodians across the globe, providing technical and commercial expertise to sustainably utilise, manage, and conserve water resources.

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