Wastewater research theme


This extensive programme area includes research on diffuse pollution, environmental impacts, treatment processes, intermittent discharges, monitoring and odour controls, collection systems and intelligence gathering, bathing waters, combined sewer overflows and effluent quality. There is a comprehensive investigation into combined sewer overflows and a series of projects carried out under the heading Priority Hazardous Substances.

This programme will also support the 21st century drainage programme led by Water UK.

Programme Lead(S)

Alex Mortlock

Severn Trent Water

Howard Brett

Thames Water Limited

Laura Shudall

Sewage Sludge
United Utilities Water Limited






Biosolids: soil quality and fertility benefits

Project Status Project Completed


Biosolids to Market. A strategic proposal to explore the threats to biosolids to land – now and in the future (SL 850/SL 1072 & SL 1060 Combined)

Project Status Project Completed

Note: As a strategic piece of work, this proposal would require clear guidance from the PSG members throughout the project’s execution to ensure that appropriate priorities are determined and used to focus the effort of successive activities and objectives

There are a growing number of reports that are driving concerns and exploratory questions regarding the suitability of the water industry’s approach to sewage sludge (biosolids) recycling and target waste stream valorisation.

These reports are making the connections between specific substances and their real or potential impacts upon the environment and/or Public Health.  It focuses attention on the wastewater industry as a consequence of our role within the current WW management system and our obligation to consider the waste hierarchy and our resulting strategies for biosolids recycling.  

While these reports may be based upon research, they can be from a single or pre-determined perspective and not holistic in their assessment – in terms of the pros and cons against all relevant stakeholders (considering those associated with the sources, pathways and receptors).

Failure to fully understand and to be able to respond comprehensively and appropriately in a timely and proactive manner, can leave us susceptible to manipulation and additional investment needs.  Not having an evidence based response to the views being expressed could force the water industry to adopt a potentially suboptimal and reactionary response to the perceived threat.

There is a significant risk that a single threat (or combination) could severely reduce or close existing routes for biosolids recycling.  This would, potentially force us to revert to the increasingly expensive and less desirable (financially and environmentally) incineration or landfill route and/or to seek alternative disposal/management routes.

In the absence of an independent and rigorous evidence base, our sector could be portrayed as failing to deliver against our overarching objectives of serving our customers and protecting the environment.  We may be regarded as co-contributors to a problem if we continue to recycle for agricultural purposes.

By taking action now, we have an opportunity to mitigate against these growing threats.  We can develop our understanding and knowledge and be in a position to:

  • fully understandthe true threats;
  • be able to respond proactively
  • with an informed response;
  • detailing the water industry requirements
  • identify the changes
  • ensure the continued protection of the environment, safeguarding public health and
  • promote the effective and efficient operation of our processes and
  • maintain our interactions within the wider system.

The range of issues that are currently gaining increased attention and which should be considered as part of the initial phase of the work, include:

  1. Sewage reduction factor substances (H1 risk list)
  2. Micro plastics
  3. Nano plastics
  4. Fibres
  5. Organic compounds
  6. Metals and inorganic chemicals
  7. Silver nanoparticles
  8. Pathogens (targeted)
  9. Combinations of concentrations of issues – as evidenced by pathogens and antibiotics & Silver nanoparticles acting as growth inhibitors of microorganisms
  10. Antibiotic/antimicrobial Resistant microorganisms 


Energy from sewers

Project Status Project submitted as Complete

There have been numerous studies, both in the UK and Worldwide, on the benefits of using sewage flow to recover usable heat via heat exchangers and heat pumps. There a number of technologies already developed to recover heat from sewers and there are a growing number of installations in Europe & North America. There is already one example of sewer heat recovery in the UK which uses Scottish Water sewers to provide heat to Borders College in Galashiels. A number of other water companies have been approached about similar projects.

With the continued support for decarbonised renewable heat through the Renewable Heat Incentive scheme it is likely that this market for sewer heat will continue to grow. This growing market poses three questions for the water compnaies:
1) What are the risks to the sewerage system or waste water treatment works from these heat recovery systems/technologies? Will some types of systems cause blockages or reduce sewer capacity? What will be the impact of reduced temperature of sewage on our treatment processes?
2) What are the legal implications for sewer heat recovery? In systems where flow leaves the sewer whose responsibility is it and are any additional permits required?
3) What is the overall scale of the opportunity for heat recovery and other forms of energy generation from sewers, both in terms of renewable generation capacity and additional income?

Currently every water company will be approaching this differently leading to possible duplication of effort and inconsistency of approach which could eventually lead to a challenge being made by those involved to Ofwat or the Government. Answering these 3 questions would help to provide a level of consistency across all water companies and a clear indication of the water industry's expectations to those  companies looking to exploit the opportunity of sewer heat recovery.


FOG Control and FOG Collection: A joined-up approach

Project Status Project submitted as Complete

This project supports the delivery of the following Water UK Water Company approved objectives (those in bold are specifically supported by this project):
- To ensure investment is affordable, focused on facilitating economic growth, and is driven by clear prioritised and phased WFD environmental and customer related outcomes.
- To successfully mitigate any current or future UWWTD related infraction risks and by demonstrating clear progress is being made in the development of our drainage systems. 
- To set out evidence based 'policy options' for Governments to consider how the existing and complex arrangements for managing drainage systems can be simplified, and in so doing reduce the costs, bureaucracy, and time taken to drive better standards of service for our customers.

To set out new practical planning and other tools as required to:
- Make our drainage systems more resilient to the impacts of climate change.
- Reduce the number of blockages and the maintenance costs for our sewerage systems (through driving behavioural changes within our customer and industrial clients and or regulatory changes so as to reduce sewer misuse).
- Design and deliver efficiently managed, resilient drainage systems fit for the future needs of customers and the environment.
The annual operational costs of jetting sewers to prevent blockages etc. is in the region of £50m. Additionally, the cost of responding to flooding is in the region of £x million, as well as the threat of very significant (highest to date was £1m fine) for pollution incidents which are now being issued against water companies for the environmental consequences of sewer blockages - Workstream 4 projects seek to mitigate and reduce these. 

The growth in the number of Food Service Establishment  (FSEs) operating in the UK over the last few decades has put an increased burden on the sewerage network and sewage treatment processes, particularly from the quantities of Fat, Oil and Grease (FOG) generated. Incorrect disposal of FOG down sinks and drains increases the risk that risk of blockages (as it solidifies) and subsequent pollutions and flooding.  While the industry has, in theory, a legal remedy to sewer blockages caused by discharges from FSEs through the WIA (and the NI and Scottish equivalents) due to the limitations of the legislation and the difficulty in identifying impact from specific dischargers it is difficult to secure successful prosecutions. 

Trade effluent legislation may be a means to more proactively control the discharges but the large number of FSEs and the legislative restrictions makes this an onerous and potentially costly proposition. There are also other legislative controls which could help reduce the impact if they are applied efficiently such as building regulations. Combined with more effective control of FSEs is the promotion and enablement of FOG collection effectively finding an alternative route for FOG.

Having a comprehensive understanding of FOG collection synergies will enable the water industry to better encourage recycling of this precious resource. 


When is ‘surface water removal’ the most cost beneficial solution?

Project Status Project Commenced

Removing surface water from foul or combined sewers offers a number of benefits, both in terms of reducing operational expenditure and flows (and subsequent flooding and spill frequency), as well as offering wider community benefits.

There is an increasing appetite across the water industry to consider and deliver such interventions to help manage a range of drivers, but this appetite is not matched by an in depth understanding of the scenarios and catchment characteristics that make surface water removal options more cost beneficial than traditional engineering solutions.


Sewer Analytics - Building On Event Duration Monitoring Expansion

Project Status Project submitted as Complete

In AMP 6 event duration monitoring (EDM) is extending significantly for all WaSCs. Whilst reporting has been a requirement for some companies since 2003, the EU issued UWWTD infraction proceedings which has promoted a drive for a change to permitting and which has left the sector in a divided state. Division has occurred because there is a proliferation of sewer monitoring equipment installed but until the Good Practice Guide was introduced the technical standards covering installation had been variable.

As a consequence, the majority of monitoring sites cannot effectively monitor volume discharged at the point of discharge thereforethe  UK has not been able to substantiate that it has complied with its deployment of UWWTD.

Draft proposals by the regulators are now seeking to apply a varied discharge permits that will use different criteria for regulating the sector. If these proposals come into play,  then the macro layer data that is used to analyse and determine such performance is essential.

It is therefore essential that technical specification of the actual monitoring data is used is clearly understood and standardised methodologies applied to the handling and analysis of such data so that it canbe reliably used to compare real data gathered with modelled performance.


Antimicrobial Resistance (AMR)

Project Status Project Commenced

Increased Antimicrobial Resistance (AMR) remains a concern for both Governments and water companies alike. AMR bacteria have been found downstream of Wastewater Treatment Works’ (WwTW) discharges in rivers and in the marine environment. It seems likely that this is not solely due to the discharge of antibiotic residues in effluent (although these may contribute to some lesser extent) but more simply, to the release of bacteria that are already resistant, or the release of genetic material containing antibiotic resistance genes (ARG) which are then incorporated by environmental bacteria.

A better understanding of the extent of resistant bacteria discharged from the WwTW and the link to anti-microbial resistance in the environment is needed, allied to quantifying the relevance of these environmental reservoirs in the context of human health. This knowledge also needs to be placed in context of the UK and Irish Governments’ AMR strategies and plans, to help to increase understanding of the contribution from the environment to the wider problem of AMR spread. Similarly, understanding the contribution of WwTW discharges relative to other environmental sources of AMR, for example, agricultural discharges, is key if we are as a society to prioritise our efforts to limit the spread of AMR.

Given the increasing importance and public concern over AMR, one of the key issues (after development of new antimicrobials) is how to prevent or limit the spread and dissemination of AMR; of specific interest to the water industry is the release of resistant organisms to the environment, and how this might impact society . WwTWs are one of a number of obvious release sources and although they achieve significant bacterial reductions, this may not be sufficient. This is particularly pertinent to bathing water discharges; although such effluents are routinely disinfected the probability of direct human exposure is far greater than for inland freshwaters.


Ecological impact of other (non soluble reactive) phosphorus fractions

Project Status Project Commenced

This project is  a follow on from the ‘recently completed 'Phosphorus speciation - does it matter?’ UKWIR project.

Feedback through this project from the Environment Agency has indicated that there would need to be evidence that the river ecology is not impacted by other species of phosphorus for them to consider an alternative method of wastewater discharge permitting based on soluble reactive phosphorus (SRP) rather than Total Phosphorus (Total P).

The opportunity would be to provide the evidence that there is/is not an ecological impact from the non soluble reactive species of phosphorus (non SRP).

Achieving compliance with the targets for phosphorus in the Water Framework Directive (WFD) is driving lower phosphorus permit limits for wastewater discharges, potentially down to 0.1 mg/l Total P. Technology to get to these very low levels is currently being trialled by the industry through the Chemicals Investigation Programme (CIP2). However, if there are alternative ways of permitting phosphorus this may change the technology required to achieve the reductions in the most relevant species of phosphorus.

If it can be proven that these other species of phosphorus do not impact the river ecology then the permitting of SRP instead of Total P may become an option resulting in the possibility of more cost beneficial solutions to achieve WFD compliance and protect the river ecology.

There is an indication from laboratory experiments that organisms have the ability to utilise normally ‘non-bioavailable’ forms of P under ‘extreme’ conditions, however further research into this is required.



Modelling a dynamic and uncertain future – preparing SAGIS for changes in climate, PR24, RBMP Cycle 3 and Brexit

Project Status Project Commenced

Source Apportionment Geographical Information System (SAGIS) is a tool developed by UKWIR that helps in quantifying the pollutant load from different sources in UK surface waters. It is primarily used by the industry and regulators in Asset Management Planning (AMP) and River Basin Management Planning (RBMP) and will remain so until at least the year 2027. It is used to determine permits for wastewater treatment works (WWTW) discharges and identify future investment needs.

The value of SAGIS and associated decision supporting tools is related to the data contained within the tool and the extent to which it incorporates the latest knowledge (scientific and political). This project will therefore focus on preparing the system for the future by including assessments of climate change, PR 24, RBMP cycle 3 and Brexit.


Research, planning and management with UKWIR’s Source Apportionment modelling system – from data to evidence and wisdom

Project Status Project Commenced

Water quality modelling underpins Water Industry decisions on securing investment to improve the aquatic environment. The SAGIS-SIMCAT modelling system is currently used by Water Companies to support decision making as part of the Asset Management Planning (AMP) cycle process, and by Regulators for River Basin Management Planning, and will continue to support these planning requirements until at least 2027.

Key benefits of SAGIS-SIMCAT are that it (i) helps to ensure that the Water Industry is not targeting capital and carbon intensive treatment solutions to address pollution arising outside of the Water Industry, (ii) provides the ability to trial the effectiveness of different measures (i.e. the ‘what if’ question), and (iii) can be used to support cost benefit analyses.

The scale of the investment by the Water Industry to improve the aquatic environment is significant, with the complexity of the challenge likely to increase. This is driven, in part, by an increase in the number of chemicals that will require active management (as suggested by findings from CIP2), but also the availability of novel and (potentially) expensive wastewater treatment technologies. It is important to deploy investment effectively to ensure measures deliver the right outcomes for Water Company customers and the environment, and SAGIS is a key tool for supporting these investment decisions.

The value of the SAGIS-SIMCAT model as a decision support tool is, however, directly related to the quality, quantity and age of data contained within the model, and also the extent to which it incorporates the latest catchment science, knowledge and understanding. The accumulation of new data and knowledge is continuous and it is critical to accommodate these within the modelling system to ensure it can continue to support current and future AMP cycle planning requirements and cost benefit analyses. This new project should therefore:

  • Incorporate findings from the latest research, for example from CIP2 (in particular).
  • Expand the frontiers of science by using SAGIS to support novel (relevant) research.

This project will be aimed at ensuring that the modelling system utilises the most up-to-date data, knowledge and information, thereby supporting both current and future AMP cycle and River Basin Management planning requirements, as well as cost benefit analyses. The benefits of this work will be realised through improved investment decision making and through the level of cooperation afforded by water companies and regulators using a common platform.


Sink to River - River to Tap - A review of potential risks from nano-particles & microplastics

Project Status Project submitted as Complete

There is significant interest in the prevalence of nano-particles and microplastics entering the environment.

There is a lack of understanding for the water industry with regards to the occurrence, fate and behaviour of these particles during transport and Waste Water Treatment; once dischrged to the river system there is limited understanding of how these particles behave; if river water is abstracted down-stream there is a lack of knowledge around the occurrenceand degree of removal of these particles through water treatment processes.


STW Flow to Full Treatment monitoring and compliance assessment method development

Project Status Project Completed

Often MCERTS flow kit is not situated at the sewage works inlet. Without a signal indicating that a spill has occurred, compliance assessment is not simple and would require investment at a large number of assets. Companies can be prosecuted for failure to meet this permit condition. In absence of any alternative accepted substitute there may be a drive for MCERTs inlet flow measurement devices to be introduced.

The Environment Agency document ‘Water Quality Consenting Standard for Flow Measurement of Discharges' states – (1) ‘For storm overflows at STWs the Agency needs to be able to confirm that the flow at which the storm overflow begins to operate is as required by the consent.’ This does differentiate between fixed weir systems and overflow settings that can be adjusted in terms of rigour applied to demonstrate compliance.

The storm overflow weir setting to the storm tanks dictates what the flows that are given secondary treatment at a conventional STW. The most recent Agency documentation detailing the theoretical calculation for this setting is ‘WaSC specific guidance: intermittents.’ This reflects the basic calculation 3PG + I + 3E, where P – population, G – water consumption, I – infiltration and E – Trade effluent flow.

In previous National Environment Programmes (NEPs), Water companies were funded to introduce MCERTs flow measurement devices with the primary purpose of measuring treated flows to receiving waters. Dry Weather Flow (DWF) compliance has been seen as the main measurement of compliance using this kit and not (1).

The location of kit has been based upon various factors such as the location of existing structures and the benefits of monitoring final effluents over raw influents etc.


Extending and updating UKWIR's pollution Source Apportionment tool

Project Status Project Completed

Water quality modelling underpins Water Industry management decisions on securing investment to improve the quality of rivers, lakes, and marine environment. The SAGIS-SIMCAT modelling system is now actively used by Water Companies to support decision making as part of the Asset Management Planning (AMP) cycle process, and by Regulators for River Basin Management Planning.

The primary benefit of SAGIS-SIMCAT is that it helps to ensure that the Water Industry is not targeting capital and carbon intensive treatment solutions to address pollution arising from other sources or sectors and is key in helping achieve an equitable split in investment between sectors, rather than loading the costs principally on the water industry. The value of the SAGIS-SIMCAT model as a decision support tool is, however, directly related to the quality, quantity and age of data contained within the model. Consequently, it is imperative to incorporate new data whenever possible. The data contained within the current version of SAGIS-SIMCAT has now aged and requires updating to maintain its credibility for planning purposes.

It is therefore necessary to ensure the modelling system and supporting databases contain the most up-to-date information available in order to support AMP cycle planning and the assessment of risks posed by chemicals of concern. It is similarly opportune to ensure there is continued support for the SAGIS user community and website to facilitate the transfer of knowledge of the SAGIS system and to extend the base of model users to new sectors, such the clean water sector, for integrated catchment management purposes.


BQ Delivering an environmentally sustainable wastewater service (that meets customer and regulator expectations) by 2050 - Phase 1 - Definition, research review and gap analysis

Project Status Project Commenced

No Further Information Available.


Wastewater briefings and alerts

Project Status Project Commenced

No Further Information Available.


Alternative approaches to Bacterial Reduction for WwTW discharges - Phase 3(Efficacy of Disinfectants)

Project Status Project Completed


Phosphorus speciation (ortho/total/SRP) - does it matter

Project Status Project Completed

This project follows on from brief work undertaken in 2014/15 to better understand phosphorus specification. That work, albeit of limited scope, identified challenges to the current regulatory approach where in essence, permits are issued to limit total P, but modelled to achieve EQSs measured as soluble reactive P (SRP). Previous work showed only a percentage of the total P to be present as SRP which may mean that permits are being set at overly-stringent concentrations?

Given the huge potential scale of future investment in P-reduction the relevance of this relationship and what it means for riverine ecology is pivotal. Additionally, the previous work identified possible shortcomings in the EA sampling and analysis methodology that may make some or much existing river data of limited value. Consequently, new permits may be issued that set unrealistic obligations and, drive unsustainable practices.

The industry needs to be fully engaged with WFD and delivering improvements that offer good value for money.  This work will help to set and deliver P-compliance requirements in a sustainable, cost-effective fashion. 

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