Flowing from Clay Pipes to Clean Water: A Short History of Wastewater Treatment

For as long as humans have gathered in settlements, we’ve faced a constant task: what to do with our waste. Across millennia, our response has evolved from primitive drainage pits to sophisticated, energy-intensive treatment systems. Yet despite thousands of years to innovate, modern wastewater treatment still relies heavily on centralised, reticulated systems first developed in the 19th century. To understand how we got here and where innovation might take us next, we must look back at the long history of sanitation.

As early as 3500 BC, the people of the Indus Valley in South Asia had developed surprisingly sophisticated sanitation systems. Homes were linked to terracotta drains, which transported liquid waste away while capturing solids in sumps – a simple but effective separation system. Similarly, the Minoans of ancient Crete used underground clay pipes, not only for sanitation but also for water supply. This was a major technological leap in engineering at the time.

“Drainage System” - Benny Lim (bennylin0724) (flickr.com) CC BY 2.0
The ancient sewerage systems used in the Indus Valley in South Asia

The Mesopotamians also developed drainage infrastructure that connected homes to early sewer systems, which were essentially long trenches that moved waste into pits. These systems were essential for public health in populated regions and set the foundations for future innovations.

Perhaps the most famous ancient sanitation innovation came from the Romans. Their engineering achievements included the Cloaca Maxima, the oldest sewer in the world, which managed both stormwater and wastewater. This sewer was built in the 6th century BC and had public baths and latrines connected to it, transporting wastewater away from these establishments, out to the Tiber River. During this period, cesspools were introduced, public toilets became common, and recycled bathwater was used to flush latrines. Wastewater wasn’t treated, but it was managed, mostly to keep Roman cities cleaner and reduce foul odours. These systems reflected the Romans’ understanding of water as a resource and as something to be managed in urban areas.

“IMG_2855 Cloaca Maxima” - Patrick Denker (pdenker) (flickr.com) CC BY 2.0
The Cloaca Maxima, still standing along the Tiber River

When the Roman Empire fell in 476 AD, so did its water infrastructure. For over a millennium, sanitation regressed. Chamber pots were emptied onto the streets, contaminating drinking water and spreading disease. With no real wastewater treatment, cities became breeding grounds for disease outbreaks such as cholera, typhoid, and the bubonic plague.

It wasn’t until the 14th Century that rules surrounding waste disposal were introduced. Cesspits became common in Europe, and laws were introduced to dispose of waste and wastewater outside city limits. But it wasn’t until the Industrial Revolution that effective sanitation returned.

The 1800s brought a period of rapid urbanisation, which, as population density became less manageable, led to deadly sanitation failures. In London, the summer of 1858 brought the infamous “Great Stink”. A heatwave demonstrated just how dire the state of the Thames was, filled with both untreated human and industrial waste. That same year, Chief Engineer of the London Metropolitan Board of Works, Joseph Bazalgette, was commissioned to build the London Main Drainage System. The project, comprised of 1,100 miles of drains to pump wastewater to ‘lost rivers’ outside the city, was completed by 1875. A substantial portion of this drainage system is still in use today, supplementing the new Thames Tideway Tunnel.

“Utilitarian” - Jon Doe (sub-urban.com) (flickr.com) CC BY-ND 2.0
The underground sewage line built in the 1800s

Through both World Wars, wastewater infrastructure stagnated. However, after World War II, there was a refocus on the disinfection and sanitation of water. In the 1960s and ‘70s, legislation like the U.S. Clean Water Act (1972) placed new limits on pollution, demanding proper wastewater treatment for the first time. Mechanical filtration, chemical treatment, and eventually biological processes became standard in reticulated, or networked, systems.

Despite this progress, wastewater treatment systems haven’t changed much since, remaining centralised, large-scale, and energy-intensive.

Wastewater systems have always been shaped by the needs and technologies of their times. Society has progressed from terracotta pipes and cesspools in our early history to reticulated systems and UV disinfection today. Yet today, communities live completely disconnected from these systems. Wastewater disappears with a flush, and few understand how, or where, it's treated. This invisibility comes at a cost. Centralised systems, while effective, are expensive to build, maintain and operate, vulnerable to disruption, and slow to adapt to changing conditions, especially in regional or remote areas.

Decentralised treatments bring visibility and ownership back to wastewater. By raising awareness of individual wastewater disposal, we can improve behaviours around flushing our waste and better manage issues such as fatbergs and blockages in our major sewers. By bringing the processing closer to the source and reducing the time between production and treatment, you also make the job of treatment that much easier, as the waste hasn’t degraded, and the water hasn’t lost its temperature.

ALGAESYS - a decentralised, modular system that fits in a simple structure.

Smaller, decentralised and modular systems, such as ALGAESYS, can be placed on-site, tailored to community or industrial needs, and powered by renewable energy. They are simpler to operate, faster to deploy, and more resilient to shocks. When the water is processed and ready to be reused, there is no additional transport or energy overhead required to get the water to where it can be used. Just as the Romans adapted their water infrastructure to their urban environment, decentralised systems today adapt to ours, supporting water reuse, reducing emissions, and increasing resilience.

The history of wastewater is one of constant innovation. Perhaps our next chapter lies not in expanding the network, but in rethinking it entirely.