National

Battling ‘fatbergs’: Tokyo’s sewers get an upgrade so they can keep on flowing

by Andrew McKirdy

Staff Writer

In September last year, a monster was discovered in London’s sewers.

Weighing about 130 metric tons and measuring 250 meters in length — longer than the city’s Tower Bridge — a congealed mass of fat, oil, wet tissues, condoms and diapers was found blocking a section of the wastewater network during a routine inspection.

The giant “fatberg,” subsequently nicknamed the “Monster of Whitechapel,” took a team of eight workers toiling nine hours a day, seven days a week, more than two months to break down. A chunk of the fatberg later went on display at the Museum of London.

But if such a leviathan was allowed to grow unchecked in the sewers below London, what are the chances that something similar is lurking beneath Tokyo?

“At one point during the 2000s, a thing like that — a big white ball of fat — got washed out to sea from the Tokyo sewers and it caused a big problem,” Hiroshi Doi, an official from the Tokyo Metropolitan Government’s Bureau of Sewerage, told The Japan Times. “So from 2001, the Bureau of Sewerage started a campaign urging people not to pour oil down their sinks.

“The most harmful thing that households or businesses can do to the sewers is pour oil down the drain — cooking oil like you would use in tempura. It starts off hot but it cools off in the sewers and congeals, then gets mixed up with rainwater and gets washed out into rivers and seas.”

Tokyo’s sewage system, which serves over 9 million people in the metropolitan area, treats an area of 627 square kilometers. If you were to lay every single sewer pipe in the city end to end, it would measure 16,000 km.

In 1971, the sewage system network covered only 38 percent of the city, and the Sumida River was nicknamed the “River of Death” because no creature was thought to be able to live there. Increased efforts by the Tokyo government to develop the system in the 1960s and ’70s brought the coverage rate up to 100 percent by 1995, and the quality of the city’s river water greatly improved as a result.

The Bureau of Sewerage, which employs about 2,500 people, is currently undertaking a program of infrastructure improvements to deal with aging sewage pipes and protect against floods. One of several works underway is the installation of a new 4.2-km-long sewer running directly beneath an existing pipe in Nerima Ward, starting in the area’s Johoku-Chuo Park.

“There weren’t so many houses around here in the 1960s and ’70s,” explained project manager Doi. “Then, as the city developed, more houses sprang up and the roads began to be paved with asphalt. Rainwater used to be absorbed into the ground but that isn’t the case any more, so more rainwater goes into the drains. If we just have one sewer pipe here, it can’t cope. So we’re making another one to share the load.”

Construction of the new sewer, which began in April 2014 and is scheduled to be completed in October 2020, involves a machine, 7.5 meters in length and 4 meters in height, drilling through the earth 18 meters below the surface.

The excavated dirt is carried away by trucks, after which workers secure the walls of the tunnel with 15-centimeter-thick steel and reinforce it with concrete. Construction advances at a rate of about 10 to 14 meters every day and is just over halfway finished.

“Technology has advanced, so the work down here is not dangerous,” said Tetsuya Emura, a technical supervisor from construction firm Tekken-Toyo Joint Venture, as he stood amid the steel lattice of the tunnel, a structure reminiscent of the Death Star space station from the “Star Wars” movies.

“Even if there was an earthquake, this has been built so that it wouldn’t have an impact,” he said. “If you were down here and there was an earthquake, you wouldn’t even feel it. You’d probably feel it more if you were above ground.”

Tokyo’s sewage system is principally made up of three facilities: sewers, which collect and carry sewage; pumping stations, where sewage is pumped up to prevent it from getting too deep; and water reclamation centers, where sewage is treated so that the cleansed water can be returned to rivers and seas.

Tokyo played host to the International Water Association’s World Water Congress and Exhibition from Sept. 16 to 21, attracting 6,000 people from 100 countries to discuss technology, public policies and sustainable water management practices.

The congress gave Tokyo the chance to showcase its water management practices to the world, with Tokyo Gov. Yuriko Koike hailing it as “a golden opportunity for Japanese companies to promote their world-leading technologies.”

Congress delegates were invited to take a firsthand look at Tokyo’s sewage system facilities, including a tour of the Sunamachi Water Reclamation Center in Koto Ward.

The facility was built in 1930, making it the second-oldest of Tokyo’s 13 water reclamation centers. It covers an area of 827,033 sq. meters — the largest in Tokyo — and has the capacity to treat 658,000 cubic meters of sewage a day, which is then discharged into Tokyo Bay.

The facility is located on a delta surrounded by the Sumida and Arakawa rivers, and treats sewage from all of Sumida and Koto wards, as well as parts of Chuo, Minato, Shinagawa, Adachi and Edogawa wards — an area populated by about 900,000 people.

Wastewater carried from households in sewer pipes arrives at the water reclamation center via the pumping station and flows into the grit chamber, where large particles are removed and sediments are allowed to settle.

The sewage then flows slowly through the primary sedimentation tank before arriving at the reaction tank, where mud containing microorganisms is added, air is pumped in and the sewage is agitated for six to eight hours. The microorganisms break down the contaminants in the sewage and cause it to form an easily submersible mass.

The mud formed in the reaction tank is then treated in the secondary sedimentation tank, where it is separated into treated water and sludge. The sludge is filtered and spun in a centrifuge to produce a “cake,” which is then incinerated into a fine ash.

“The facility is impressive,” said Risto Saarinen, a water utility manager from Finland who was visiting the Sunamachi facility as part of the IWA tour. “The wastewater treatment is advanced. I would have expected a little bit more technology level because the Japanese are good at technology.

“It was what I would call conventional, given that we are in a developed country. I’ve seen technologies which have gone further than this. It looked a little bit old-fashioned but the treatment results were alright. What was impressive was the cleanliness. That was really a nice feature.”

Also housed within the Sunamachi facility is the Sewerage Technology Training Center, which provides Bureau of Sewerage staff with hands-on experience on exact, scale replicas of actual equipment.

Trainees can wade through water, practice going in and out of manholes, gain an understanding of wastewater treatment and take part in an emergency simulation — where participants must respond to the situation as it unfolds in real time.

“That was really impressive,” said Saarinen. “Here you can really press the buttons and start the engines by playing with the system. I’ve seen similar ones in nuclear power plants and they have huge control rooms. Someone simulates the process, putting new trouble into the system, and the trainees have to react.”

The training center is essential to the Bureau of Sewerage’s operations because a large number of employees who were hired in the 1960s and ’70s retired between 2000 and 2010. The bureau has responded by hiring more and more people every year since 2009, but the ratio of veteran employees guiding recruits with less than five years’ experience dropped from 13-1 in 2007 to 3-1 in 2016.

A shortfall of experienced staff members is just one of the myriad challenges the organization faces.

“The Bureau of Sewerage is compiling a management plan, and within that is the reconstruction of old sewer pipes,” said Doi. “The Tokyo sewage system was built all at once to cope with the city’s economic growth and sudden increase in people, so everything is wearing out at the same time.

“Then we have rainwater and protecting against floods. The Tokyo system is also like London in that we have a combined sewage system that collects rainwater and wastewater together, so that has to be improved. We are also involved in protecting the sewage system from earthquakes.”

Japan’s wastewater management know-how has been put to use overseas in water surface control devices in Europe and infrastructure development projects in Malaysia.

The IWA Congress gave Japan’s wastewater management industry a further chance to cement its international ties, and incoming IWA Vice President and current board member Sudhir Murthy was impressed by what he saw.

“I’ve seen how pristine Japan is and how water is so well managed in this country,” he told The Japan Times on the last day of the congress. “I’ve seen the spiritual dimension of water here. Water isn’t just a commodity; it’s part of the spiritual life in this country. If you look at how the governor of Tokyo talks about water, it is beyond the mundane. It’s part of the spiritual ethos.”