Waste water and industrial outfalls

Water which has been contaminated by human activity or use is ‘waste water’. Use can be in any activity, including runoff or personal domestic uses, such as sewage waste water. Waste water treatment is the processing of contaminated or ‘dirty’ water in order to dispose of it while protecting the environment and human health. Disposal can be into marine or riverine environments.

Waste water or sewage in raw form could be extremely damaging in the marine environment. Excessive nutrients (such as phosphorous and nitrates) could cause eutrophication (see Eutrophication), while other chemicals may be directly toxic, or cause harm to humans through seafood or bathing.

Information in the Bathing waters, Eutrophication, Transitional and coastal watersShellfish waters, and other sections within the Clean and Safe chapter of the Solway Review will be relevant for waste water, given that waste water can have implications for other elements of a clean and safe marine environment. Bathing water profiles, for example, for each of the designated bathing waters in the Solway will include information on pollution risks from sewageSanitary surveys for Classified Shellfish Harvesting Areas look at pollution sources. They are highly relevant for information about continuous and intermittent waste water outfalls located in the vicinity of survey sites.


Image; Port Logan © G.Reid/ Solway Firth Partnership.

The purpose of waste water treatment is to process and discharge waste water while also protecting both environmental and human health.

Outfalls of waste water into the marine environment fall into three categories;

  • waste water treatment (WWT) plants,
  • industrial outfalls, and
  • private waste water treatment systems (such as septic tanks).

All are subject to strict environmental control and the volumes discharged are small compared with the receiving sea area. Waste water also discharges into a variety of other surface waters such as rivers, which will reach the sea. Waste water services are provided (primarily) through Scottish Water in Scotland, a statutory corporation accountable through the Scottish Government, and through the United Utilities public limited water company in Cumbria. The Scottish Environment Protection Agency (SEPA) and the Environment Agency (EA) manage permits for land-based water discharges out to 3 nm and work with the agricultural sector on good farming practices in order to minimise excess nitrate pollution.

Treatment levels are set out through The Urban Waste Water Treatment Directive 1991 (UWWTD) (Council Directive 91/271/EEC) for WWT outfalls. Population equivalent (pe) of the plant catchment and the sensitivity of the water receiving the discharges are the factors which determine treatment level. There is an interactive storymap available from the European Environment Agency showing the types of treatment reported at urban waste water treatment plants for agglomerations ≥ 2 000 pe and other information on the implementation of the UWWTD. The interactive map is available here. It is worth noting that; ‘in exceptional circumstances (i.e. large storms) Secondary or Tertiary treatment may be bypassed and untreated or only primary treated waste released’ (Moffat et al, 2020).

As discussed in the Bathing Waters section of the Solway Review, some sewage systems also collect rainwater. The risk of outfall pollution events is particular high after heavy rainfall due to the combined sewage pipes used by both Scottish Water and United Utilities. The Combined Sewage Overflows (CSOs) are designed to release overflow water through a separate pipe during storm events. These overflow systems are described by United Utilities; “With a sewer overflow in place, the rain water, mixed with sewage, will rise inside the sewer and eventually enter a separate pipe which runs off the main sewer and flows into a river or the sea” (United Utilities, n.d.). The overflow is necessary to limit flooding risks.

Private WWT systems such as septic tanks or small sewage treatment plants in England must adhere to the general binding rules, or require a permit. The general binding rules which must be met for discharging waste water into surface water, including estuaries or coastal waters, are available here. They require septic tanks which discharge into surface waters to use a sewage treatment plant. By law in Scotland septic tanks must be registered with SEPA, more information is available here.

Industrial discharges around the UK are licensed by SEPA and the EA. In Scotland, industrial effluent discharges are licensed if the volume of effluent is >10m 3/day and has a population equivalent >15. The nature and amount of discharge are subject to control. SEPA regulates such outfall discharges through The Water Environment (Controlled Activities) (Scotland) Regulations 2011 (CAR Regulations).

Information on pollutants released through industrial activity are monitored and recorded through the Scottish Pollutant Release Inventory (SPRI), which is a Pollutant Release and Transfer Register (PRTR). PRTRs must be publicly available, required by the 2003 Kyiv Protocol on PRTRs. The SPRI is a database of annual releases from SEPA-regulated industrial facilities of specified pollutants to air or water. More information on the SPRI is available here. The UK also has a Pollutant Release and Transfer Register of chemicals or pollutants released to air, water and soil and transferred off-site for treatment, including where, how much and by whom. The UK PRTR is the publicly available register that implements the Kyiv Protocol and UK PRTR legislation. SPRI and the UK PRTR are both publicly available and fulfil reporting requirements of the European Pollutant Release and Transfer Register. The UK PRTR from the Department for Environment Food and Rural Affairs (DEFRA) is available here.

There are a variety of small and large industrial activities which have marine discharge outfalls throughout the UK. A list of the number of outfalls from small and large industrial activities throughout Scotland is available in Scotland’s most recent Marine Assessment (Moffat et al, 2020) here.


Video; Dhoon Bay bathing water. © Solway Firth Partnership.

Waste water and industrial outfalls

In the Solway



SEPA issues licences for disposal in coastal waters. Waste data reporting publications are available from SEPA here. There is an extremely helpful interactive map from SEPA for annual compliance assessment of SEPA licensed activities. This includes private and public wastewater licences, available here.

In 2018 in Dumfries and Galloway, the overwhelming majority of WWT outfalls were small discharges (<15,000pe) with there being 52 outfalls. There are only 4 larger secondary WWT treatment plants with a capacity between 15,000 and 100,00pe. There are 56 outfalls for WWT in the Solway marine region (Moffat et al, 2020). This does not include data on domestic discharges from private systems such as septic tanks. Given the fact that Dumfries and Galloway is a rural area, with many small towns and individual or small groups of houses, there are many septic tanks throughout the region. There are also 6 marine discharge outfalls for small industrial activities, 4 are classed as the regulated activity ‘other effluent’, and 2 as ‘other effluent food processing’ (Moffat et al, 2020). There are also 2 large industrial activities, categorised as ‘chemical industry’ (1 outfall at Annan) and ‘Animal and vegetable products from the food and beverage sector’ (1 outfall at Loch Ryan).

In the early 2010’s Scottish Water undertook the ‘Loch Ryan project‘. This £25 million project upgraded the waste water treatment and sewer network for towns and villages close to Loch Ryan, such as Cairnryan and Kirkcolm, Leswalt and Stranraer. As part of the project a state of the art sewage treatment plant was installed at Smithy Hill. This plant has helped improve the water quality in Loch Ryan, with the sewage from these areas being processed at Smithy Hill, and discharged into the north channel of the Irish Sea on the west coast of the Rhins.

Scottish Water currently has plans to improve Annan’s waste water network in 2021. These plans aim to reduce sewer flooding which can happen as a result of heavy rainfall. They are also in the process of planning upgrades to the Wastewater Treatment infrastructure in Kippford, including a new wastewater treatment works and outfall. These multimillion-pound improvements will help improve Rockcliffe’s bathing water and help protect the Urr estuary. Updates on these improvements are available here. Scottish Water also has an interactive map which provides details on all of the investment plans, flash flooding, and supply issues throughout Scotland, available here. Some sewage outfalls in close proximity to bathing waters are discussed in bathing water profiles. For example; Sewage effluent discharge at Saltpan rocks and further upstream at Barnhourie Burn (Sandyhills Bathing Water Profile). A new WWT works is also being constructed and is set to open this year in Canonbie. Although Canonbie is not on the Solway coast the WWT works will help protect the environment of the River Esk, which eventually flows into the Solway.



Unlike in Scotland where water and sewage services are provided through a statutory corporation accountable through the Scottish Government, in England and Wales these services are provided through 32 private companies which have statutory obligations, following privatisation in 1989. There is a regulatory framework in place which oversees, licences and monitors these companies to ensure a fair price and standards. Ofwat is the economic regulator of the water sector in England and Wales, DEFRA sets the policy framework (in England) and the EA is the environmental regulator (in England) for the sector. For example, the EA regulates intermittent discharges from sewer overflows and waste water treatment works through environmental permits.

United Utilities is the public limited water and sewage company in Cumbria. United Utilities has an official appointment (licence) as a water and sewerage undertaker through the Water Act 1989. The most recent version of this appointment is available here, and includes a map of the area concerned. This company covers water and sewage for an area far exceeding the Solway Firth. It serves almost 3.5 million households including large urban areas such as Liverpool and Manchester, covering the whole of the north west of England from Cumbria to Cheshire.

The EA issues licenses for carrying out certain activities that have the potential to pollute the environment. A permit is required for most discharges into surface waters under the Environmental Permitting Regulations. There is a Public Register of discharges to water through DEFRAs online data platform. This includes United Utilities discharges and is available here. Please note that the register also includes revoked permits, those which are revoked include a ‘Revocation Date’ as well as a start date in the register.


Image; Water exit pipes © Solway Firth Partnership. Photographer; K. Kirk

Waste water and industrial outfalls

Economic Contribution



According to Scotland’s Marine Assessment (Moffat et al, 2020); ‘The disposal of waste water at sea is an ecosystem service, creating the benefit of costs saved compared to alternative means of disposal. The value of this benefit cannot be calculated with certainty.’

The Waste Water and Industrial Outfalls section has been included in the Productive chapter of Scotland’s Marine Atlas, Scotland’s Marine Assessment and the Clyde Marine Region Assessment. However, in Scotland ‘waste water treatment and industrial outfalls do not generate economic value in their own right and their contribution, in terms of GVA or employment, is therefore not included in the Scottish Annual Business Survey. There is no direct information on employment in waste water treatment as Scottish Water, who run the vast majority of public waste water treatment works, only publish total employment numbers. At the end of March 2019 Scottish Water directly employed 4,276 people and a further 404 temporary agency workers’ (Moffat et al, 2020).

SEPA generates income from the licences issued for disposals in coastal and transitional waters, 738 of these licences were issued in 2019, totalling an income of £7.1 million. Some outfalls may not be in operation, and licences may cover multiple outfalls (Moffat et al, 2020).

Scottish Water’s investment programme aims to deliver improvements to the waste and water infrastructure in Scotland. In the 2015-2021 programme Scottish Water sought to deliver £3.9 billion of improvements (Scottish Water, n.d.). Scottish Water’s major improvements along the Scottish side of the Solway are detailed above.



United Utilities employs over 5,000 people but this is throughout the entire north west region of England. With 575 wastewater treatment works and 96 water treatment works covered by United Utilities, employees will be spread throughout the region and a large number will be within the head office located in Warrington, Cheshire.
Whitehaven has a large United Utilities call centre with around 200 members of staff (News and Star, 2020).

The Companies House information for United Utilities International Limited defines the nature of the business with SIC code 36 (in addition to Head Office activities), however jobs related to sewage (SIC code 37) in the local council areas of Carlisle, Allerdale and Copeland are also relevant. The Business Register and Employment Survey (BRES) provides employee numbers, the Standard Industrial Classification (SIC) codes (Office for National Statistics, 2007) used are 36: Water collection, treatment and supply, 37: Sewage.

There are very few part-time jobs in these industries in Cumbria as a whole. There were around 10 and 15 employees in 2019 in water treatment and sewage respectively throughout Cumbria County Council. None of the smaller local authority areas (Carlisle City, Allerdale Borough, Copeland Borough) recorded any part time positions in the BRES for either water collection etc, or sewage between 2015 and 2019 apart from Allerdale Borough in 2019, where there were 10 part time employees in sewage. These employee numbers, however, will not fully account for the employees of United Utilities’ call centre in Whitehaven as they may be recorded under the activities of head office or call centre SIC codes.


Total Employees (rounded) for Waste Water Collection Treatment and Supply in (SIC code 36)

Local Authority/ County Council 2015 2016 2017 2018 2019
Carlisle City 50 50 50 50 50
Allerdale Borough 50 50 100 100 100
Copeland Borough 10 10 10 20 10
Cumbria County Council 300 300 300 400 400

(Source: Office for National Statistics (Various) (BRES))


Total Employees (rounded) for sewage (SIC code 37)

Local Authority/ County Council 2015 2016 2017 2018 2019
Carlisle City 0 10 0 10 50
Allerdale Borough 0 40 20 20 30
Copeland Borough 0 0 0 0 0
Cumbria County Council 25 100 50 75 125

(Source: Office for National Statistics (Various) (BRES))


Water companies in England also invest in improvements to their infrastructure and assets. The 5- yearly ‘price review’ is where Ofwat sets performance targets such as pollution incident reduction, and wholesale price limits (Hutton, 2020). The process includes the EA working with ‘water companies, Ofwat and others to make sure that investment protects the water environment, increases resilience and secures long-term benefits for society and the economy. The Environment Agency sets out the environmental obligations, including work required to prevent deterioration and achieve protected area and water body status objectives’ (Scottish Environmental Protection Agency, 2015).

According to the Solway Tweed River Basin Management Plan (RBMP) 2015 update, investment in the Solway Tweed River basin district by water companies between 2015 and 2020 was set to be around £70 million. This investment was to address ‘point source impacts from sewage treatment works and discharges from the sewer network. This will reduce pollutants such as ammonia and nutrients that disturb the natural ecological balance of water bodies and cause excessive growth of vegetation and algae’(Scottish Environmental Protection Agency, 2015).

There is guidance available from the EA on ‘Water companies: environmental permits for storm overflows and emergency overflows’, available here. Water companies need to identify storm overflows that need improvement. The EA can review permits and take enforcement action if an overflow reaches unsatisfactory condition in breach of permits.


Image; Whitehaven © Solway Firth Partnership

Waste water and industrial outfalls


The waste water and industrial outfalls activities have positive and negative socio-economic and environmental aspects in both Scotland and England.

Positive socio-economic aspects of these activities include; employment, providing necessary societal service and infrastructure, and ensuring a clean environment. Overflows help to reduce the risk of flooding during significant storm events, which would otherwise cause damage. However, failures or overflows can cause pollution and counteract the final positive point of ensuring a clean environment. Overflows in particular have the potential to cause negative environmental impacts, mentioned below, which also may negatively impact socio-economic aspects. Furthermore, outfalls can impact other activities through possibly obstructing the seabed or nutrient enrichment.

There are no positive environmental impacts from waste water and industrial outfalls as it is not an activity which seeks to improve the condition of the marine environment, but seeks to ensure it limits negative impacts. Successful waste water treatment with correct treatment and practices will provide a means for disposal without negatively impacting the environment. However, there is the potential for hazardous substances, excessive nutrients and organic matter and litter to be introduced to the marine environment through these activities. The addition of litter and organic matter can be seen as a result of storm events causing outflow from combined sewage overflows. Scotland’s Marine Assessment (Moffat et al, 2020) uses the Feature Activity Sensitivity Tool to identify a list of pressures on the environment from both industrial and agricultural liquid discharges and sewage disposal. In addition to the three noted above the list includes pressures such as; temperature change, barrier to species movement, salinity changes, and reduction to the availability or quality of prey.


Image; Balcary © Solway Firth Partnership

Waste water and industrial outfalls

Water Framework Directive

The statutory process of updating River Basin Management Plans (RBMPs) is being progressed by SEPA for the cross border Solway Tweed RBMP and the EA for the North West RBMP (covering the western part of the English side of the Solway). Updated plans are due at the end of 2021 and will set out the aims and objectives to protect and improve the water environment from 2021 to 2027.

SEPA and the EA are also competent authorities for the Water Framework Directive (WFD) (2000/60/EC) (WFD) assessment on water quality. The update to the RBMP for the Solway Tweed river basin district in 2015 detailed the improvement needs for waste water discharges in the cross-border river basin. RBMPs create a single system of water management on a river basin level which allows for coherent planning regardless of administrative boundaries. All water bodies have the objective to reach ‘Good status’ by 2027 in line with the WFD.

Once a River Basin Management Plan has been published ‘programmes of measures included become statutory requirements and [in England] the Environment Agency… will use permit and license conditions to ensure that water and sewerage companies deliver their agreed contributions. This is relevant to drainage planning because misconnections, blockages, mechanical failure, sewer flooding and Combined Sewer Overflows (CSOs) can all contribute to the deterioration of water quality and the failure to achieve good ecological status or meet environmental quality standards for priority substances’ (Ofwat, 2013).

Scotland’s Marine Assessment clarified that; ‘Scottish Water is working with SEPA to plan and phase investments so that they can manage their resources to ensure they can fulfil their obligations by 2027’ (Moffat et al, 2020).


Waste water and industrial outfalls


Baxter, J.M., Boyd, I.L., Cox, M., Donald, A.E., Malcolm, S.J., Miles, H., Miller, B., Moffat, C.F., (Editors), (2011). Scotland’s Marine Atlas: Information for the National Marine Plan. Marine Scotland, Edinburgh. pp 191. Available here. (Accessed: 22.07.19)

Department for Environment, Food and Rural Affairs (2018). Defra magic map. Available here (Accessed: 03.10.18)

Environment Agency (2020). Public Registers. Available here. (Accessed:12.05.21)

Environment Agency (2020). United Utilities Environmental Performance Assessment 2019. Available here. (Accessed: 12.06.21)

Environment Agency (2018). Water companies: environmental permits for storm overflows and emergency overflows . Available here. (Accessed: 12.04.21)

European Commission (n.d.) Facts and Figures about Urban Waste Water Treatment. Available here. (Accessed: 15.12.20)

European Environment Agency (2020). Urban Waste Water Treatment Map. Available here. (Accessed: 12.04.21)

Marine Management Organisation. (n.d). Marine Planning Evidence Base. Available here. (Accessed: 14.05.18)

Marine Scotland (n.d.). Scotland’s National Marine Plan Interactive. Available here. (Accessed: 06.08.19)

Mills, F., Sheridan, S. and Brown S., (2017). Clyde Marine Region Assessment. Clyde Marine Planning Partnership. pp 231, Available here. (Accessed: 14.05.18)

Scottish Environmental Protection Agency (2015). Water Environment Hub. Available here (Accessed: 03.10.18)

Solway Firth Partnership (1996). The Solway Firth Review, Solway Firth Partnership, Dumfries. Available here. (Accessed 23.07.19)

Tagholm, H., Slack, A. & Field, A. (2020). Surfers Against Sewage, 2020 Water Quality Report. Available here. (Accessed: 10.04.21)


In-Text References;

Hutton, G. (2020). Economic regulation of the water industry in England and Wales, Research Briefing, House of Commons Library. Available here. (Accessed: 12.05.21)

Moffat, C., Baxter, J., Berx, B., Bosley, K., Boulcott, P., Cox, M., Cruickshank, L., Gillham, K., Haynes, V., Roberts, A., Vaughan, D., & Webster, L. (Eds.). (2020). Scotland’s Marine Assessment 2020. Scottish Government. Available here. (Accessed: 10.04.21)

News and Star (2020.) Colley, J., United Utilities’ Whitehaven call centre staff raise cash for Mirehouse Residents’ Group. Available here. (Accessed: 28.06.21)

Office for National Statistics (Various). Business Register and Employment Survey (BRES). Available here. (Accessed: 28.06.21)

Office for National Statistics (2007). Standard Industrial Classification of Economic Activities. Available here. (Accessed: 22.07.20)

Ofwat (2013). Drainage Strategy Framework – For water and sewerage companies to prepare Drainage Strategies. Available here. (Accessed: 13.05.21)

Scottish Environmental Protection Agency (2015). The river basin management plan for the Solway Tweed river basin district: 2015 update. Available here. (Accessed: 13.04.20)

Scottish Water (n.d.) Investment Programme. Available here. (Accessed: 16.06.21)

The Rivers Trust (2020). Consented Discharges to Controlled Waters (filtered to highlight discharges to estuary/tidal rivers or sea) Available here. (Accessed: 14.03.21)

United Utilities (n.d.). Combined Sewer Overflows. Available here. (Accessed: 10.11.20)


Image; Beckfoot © Solway Firth Partnership.