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From miasma to mismanagement: The dirty truth about UK sewage

Civil Engineering By Marko Amezaga-Kutija, Engineer, Civil Engineer – 20 April 2023

Water flowing out of sewage pipe.


Headshot of Marko, in front of a timber and plant wall.

Marko Amezaga-Kutija

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History of sewers

As cities continue to redevelop and grow with a push towards more sustainable construction, the need to develop on brownfield sites becomes a necessity that comes with a unique set of challenges. Prior to the industrial revolution, many UK cities dumped their raw sewage directly in rivers at the detriment of public health. In London, the construction of an expansive sewer network by Joseph Bazalgette following the 1858 "great stink" marked a period of investment in drainage infrastructure. With the push for rapid growth along with the belief that the bad smell of sewage caused health issues (via a “miasma”), other cities saw similar investment in drainage infrastructure.

Archive sewer records

The UK water supply and sewerage was privatised at the end of the 1980s. The transfer of responsibility of sewers to the sewage undertaker didn’t take place until the Water Industry (Schemes for Adoption of Private Sewers) Regulation of 2011. These changes in ownership and the digitalisation of historic inaccurate records have led to information being misreported and, in some cases, lost. How dysfunctional the system is can be seen through the inability of some water companies to supply accurate sewer locations. In some cases, these are still being provided as pdfs that do not include any sewer depths.

Ownership of the problem

This missing information causes delays and adds additional expenses to construction on brownfield developments. This is due to the need for further survey investigations to minimise the likelihood of damaging existing infrastructure. What happens if a sewer is damaged? And who is responsible for paying the cost? The subcontractor, the main contractor, the developer? Or does it all come back to the government and not forcing sewage undertakers to have accurately mapped assets? There is no black and white response, and the situation shows no sign of improving as there is no incentive for water companies to map these assets any further.

Privatisation of sewerage networks

One of the reasons given for privatisation was to allow for a more efficient industry financed by private sources (the paying public). This initial led to a wave of investment, in part to catch up with stringent environment legislation from the European Union. However, nearly 35 years later, we have debt riddled private water companies with seriously underperforming sewage infrastructure. The only major investment in drainage infrastructure in the UK since privation (Thames Tideway Tunnel) has required governments intervention to secure its funding.

Raw sewage is still discharging to our water ways

As I'm writing this blog, there is a headline on the BBC stating, "Water companies released raw sewage into rivers and seas in England for more than 1.75 million hours last year." There have been multiple high-profile investigations which led to fines being handed out to water utilities for raw sewage dumping in rivers. But something must be wrong if companies can afford to continue to reoffend, instead of solving the problem. A key aspect of privatisation was the establishment of an economic and environmental regulator (OFWAT – Office of Water Services setup to protect the interests of the costumer, and the EA – Environment Agency), who should have ensured the sewage network is fit for purpose. Why has this failed?

Political Influence

Currently there is speculation in the media that the government is looking to use its post Brexit powers to repeal two key pieces of river water quality legislations that were inherited from the EU (the Bathing Water Regulation and Water Framework Directive). This follows on from the government pushing back the target date of 2027 to achieve a good standard of river quality set out by the Water Framework Directive to 2063.

Role of the civil engineer

The underlying issue is that the industry needs to bring the overstressed and outdated Victorian infrastructure into the 21st century. We all have a duty to do our part in reducing the stress on the existing sewage networks by not flushing wet wipes or fats and oils down the drain. As civil engineers, there is much more we can do.

The simplest way is to reduce the amount of discharge entering the combined system is by splitting surface water and foul water connections. Although this is a requirement for all new developments, the connection point for many sites is into a combined sewer.

The second option is to reduce the flow with infiltration sustainable drainage systems (SuDS), such as soakaways or reusing on-site as greywater via rainwater harvesting techniques.

A third option is reducing the peak discharge from developments to reduce the strain on the network at the critical duration, which reduces the risk of combined sewer overflows (CSOs) overtopping. This can be achieved by providing SuDS features such as, green roofs, rain gardens, basins and ponds which all have further qualities of reducing pollutants in the water and boost local biodiversity.

I believe it is the responsibility of all stakeholders to improve the recording, construction, and quality, led by government change to hold everyone to account, but now we can only do our part and raise awareness.