The facility that is cleaning up Victoria Harbour

The facility that is cleaning up Victoria Harbour

Coral has returned to Victoria Harbour and Hong Kong's beaches are safe for swimming again, thanks to this sewage treatment plant

hong kong sewage treatmentVictoria Harbour is looking better than ever thanks to some clever sewage treatment.

Can you imagine taking a swim in Hong Kong’s notoriously polluted Victoria Harbour?

Believe it or not, it’s possible. And your skin won’t even fall off. That’s what two swimmers from the Hong Kong Amateur Swimming Association found this month when they tested the waters in advance of a cross-harbour swimming tournament the association hopes to restore before the end of the year.

The smell gets worse in the summer. Most people would consider this unpleasant, but it makes us very happy. — Tse Chi-shan, overseer at the Stonecutters Island Sewage Treatment Works

Thanks to the Harbour Area Treatment Scheme (HATS), which was first launched in 2001, water pollution is quickly becoming a thing of the past.

E. coli levels in Victoria Harbour dropped by more than 57 percent last year alone, a trend that analysts from both the government and Hong Kong’s universities expect to accelerate in the years to come.

The effect has been tangible. Marine life has returned to the harbor, including coral, which was spotted in the harbor for the first time in decades.

Seven beaches in Tsuen Wan, which were closed in the 1990s and early 2000s as water pollution increased, are once again safe for swimming. Four of them will re-open this summer; the others will open in a few years after new swimming facilities are built.

These positive changes are the result of a new sewage treatment plant. Until 2001, raw sewage was dumped straight into the harbor, giving it a particularly grim appearance and a rather musky smell.

Now, sewage throughout Kowloon and the New Territories is diverted and sent to the massive Stonecutters Island Sewage Treatment Works.

Hong Kong Island still dumps 450,000 tons of raw sewage into the harbor every day, but that will stop by 2014, when 21 kilometers of new tunnels will link the island with the sewage treatment plant. When the entire system comes online, it will serve more than five million people.

To see what’s behind this ambitious cleanup of Hong Kong’s once-putrid seawater, we paid a visit to Stonecutters Island, where we were greeted by Lawrence Ho, senior engineer in charge of the HATS scheme, and Tse Chi-shan, who oversees the sewage treatment plant. 
hong kong sewage treatmentTse Chi-shan (left) and Lawrence Ho make sure all is right at the sewage treatment plant.
“The smell gets worse in the summer,” says Tse as we walk past a series of tanks that take in 1.4 million cubic metres of sewage every day. “Most people would consider this unpleasant, but it makes us very happy, because it’s the smell of healthy sewage that has lots of oxygen.”

Though there is a distinct acrid scent to the air, it doesn’t smell nearly as bad as the foul stench that occasionally pervades Hong Kong’s streets.

“When you are in the streets, and you smell something revolting, it’s because sewage has gotten blocked up somewhere nearby and turned septic,” explains Tse. “It’s what we call dead water, because it is stagnant and bacteria consumes all of the oxygen and then all the nutrients. That’s when it gets so, so stinky.”
hong kong sewage treatmentTreatment tanks, the stinkier the better.
The sewage treatment process is fairly straightforward. When you flush your toilet, the wastewater travels to one of several primary treatment plants located throughout the city, where it passes through a series of screens that filter out debris.

The water is then sent on its way to Stonecutters Island, where it is pumped into huge flocculation tanks where it is mixed with two chemicals, ferric chloride and an anionic polymer. After the water is transferred to another tank, the chemicals cause the pollutants to settle into a thick sludge.

“Then, in layman’s terms, we scrape it to the side,” says Tse.
hong kong sewage treatmentSludge. Not concrete.
“Don’t be fooled by the sludge,” says Tse. “It might look solid, but it’s still water, so you can’t walk across it.”

Life buoys are found throughout the treatment plant.

“Luckily, we’ve never had to use them,” says Tse.
hong kong sewage treatment
hong kong sewage treatment
After the sludge is scraped away, it is sent to holding tanks where it is eventually compressed into slabs and sent to incinerators. The remaining water is disinfected by chlorine, then dechlorinated and sent out to sea.

This deceptively simple process manages to reduce the amount of E. coli in the water by 99 percent, while other pollutants are reduced by 70-80 percent. The treated water also contains 10 percent more dissolved oxygen, which is crucial to the survival of marine life.

After 2014, another biological disinfection stage will be introduced, cleaning the water even further.
hong kong sewage treatmentControl room.
The entire harbor-area sewerage system is overseen from the Stonecutters Island control room. Two employees work there around the clock on shifts, monitoring live camera footage from inside treatment plants and real-time information about water flow.
hong kong sewage treatmentChlorination tanks.
Until a little over a decade ago, Hong Kong’s sewage treatment process stopped at the first step: rubbish, grit and other physical debris was filtered out of the water, but all of the bacteria and toxins were simply flushed out to sea.

“The harbor has a self-cleansing effect because it’s open to the sea and has strong currents, but it doesn’t work if you overload it with pollutants, which is what happened from the 1970s to the 1990s,” says Ho.

 “We’ve seen a big improvement because of the treatment works. It’s only natural. If you stop dumping raw sewage into the harbour, it can only be a good thing.”


Christopher DeWolf is a writer, photographer and self-styled flâneur.
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