Where Does Your Sewage Go? | I Didn't Know That

Summary

The video explores the inner workings of Becton Sewage Treatment Works, Europe's largest facility, handling sewage from 3.4 million Londoners. Tracing the journey from London's network of pipes to advanced treatment, it showcases how modern technology transforms raw waste into clean water in just four hours. Large debris is removed and sent to landfills, while primary tanks separate solids from liquid. In secondary biological treatment, billions of bacteria break down remaining materials with oxygen-rich aeration. Solid sludge is processed into a 'sludge cake' and incinerated, supplying 75% of the plant’s energy needs, highlighting both innovation and sustainability in modern sewage management.

Takeaways

• 🚰 London's sewage is carried away through a network of interconnected pipes, originally designed by Joseph Bazalgette.
• 🏭 Becton Sewage Treatment Works in East London is Europe's largest sewage treatment facility.
• ⏳ In the 19th century, sewage was merely stored in tanks and pumped out at high tide, but modern treatment is far more advanced.
• 💧 Today's treatment process takes just four hours to make sewage clean enough to return to the river.
• 👥 The works handles sewage from 3.4 million Londoners, equating to 34 Olympic swimming pools every hour.
• 🧹 Large objects like bricks, wood, rags, and even parts of cars are removed at the inlet works before treatment continues.
• ⚙️ Primary settlement tanks remove solid organic material via a moving bridge with surface skimming and bottom dredging blades.
• 🦠 Secondary biological treatment uses billions of bacteria to break down dissolved materials, aided by aeration with high-pressure oxygen.
• -
• ✅ Treated effluent is tested to ensure it is safe to return to the Thames.
• 🔥 Solid sludge removed earlier is processed, filtered, and incinerated, providing 75% of the power needs for the treatment works.

Q & A

Who was responsible for designing the original sewage system in London?

Joseph Bazalgette, a pioneer in sewage engineering, designed and built London's original network of interconnecting sewage pipes.

What is the name and location of the sewage treatment works featured in the video?

The video features Becton Sewage Treatment Works, located in the east of London, which is Europe's largest sewage treatment facility.

How has sewage treatment evolved since the 19th century?

In the 19th century, sewage was simply stored in tanks and pumped out to the river at high tide. Today, treatment processes are more advanced and refined, allowing sewage to be cleaned and returned to the river in about four hours.

How much sewage does Becton Sewage Treatment Works handle daily?

The facility handles sewage from 3.4 million Londoners, which equates to approximately 34 Olympic swimming pools of sewage every hour.

What is the purpose of the inlet works and the large screens?

The inlet works use large screens to collect and remove big objects such as bricks, wood, rags, and even items like towels or half a car. These are washed and sent to nearby landfill sites.

What happens in the primary settlement tanks?

In primary settlement tanks, sewage flows slowly over the tank, while a moving bridge with two blades removes solid organic material. The top blade skims scum from the surface, and the bottom blade dredges heavier sludge from the tank bottom for further processing.

How does the secondary biological treatment process work?

During secondary treatment, sewage is mixed with billions of bacteria, which degrade remaining dissolved materials. High-pressure air pumps dissolve oxygen into the sewage, accelerating the biological breakdown process.

What happens to the treated effluent?

The treated effluent is tested to ensure it is clean enough before being released back into the River Thames.

How is the solid sludge processed after removal?

The solid sludge is taken to a processing plant where it passes through a filter press to remove water, creating a sludge cake that is then incinerated.

How does the treatment plant generate part of its power?

The incineration of the processed sludge cake generates 75% of the power needs for the entire Becton Sewage Treatment Works.

Why is pumping air into the sewage important in biological treatment?

Pumping air into the sewage saturates it with dissolved oxygen, which accelerates the bacteria-driven biological breakdown of remaining organic materials.