Thais flocked to rivers and lakes on Friday evening to release small floats adorned with flowers and candles in an annual festival honoring the goddess of water, with thousands of the tiny boats ending up clogging and polluting the country’s waterways.

Within hours, workers began trawling the rivers to fish out the offerings, as paying tribute to the divinity is increasingly proving to be ecologically hazardous.

The Loy Krathong festival allows believers to symbolically float their misfortunes away on “krathongs” and start another year of life with a clean slate. The festival is celebrated on the night of the full moon of the 12th lunar month, which traditionally marks the end of the rainy season.

Thon Thamrongnawasawat, a leading Thai marine biologist, said getting people to stop using harmful materials such as polystyrene foam — Styrofoam — for their floats remains the priority because they cause the most damage to the water and aquatic life. The number of endangered sea creatures found dead ashore, which he believes stems from the problem of ocean trash in Thailand, doubled from 2017 to 2020.

Activists have noted a change in people’s behavior over decades, pointing to rising awareness of the damage krathongs cause. The total number of krathongs collected in Bangkok has fallen from over 900,000 in 2012 to just over 490,000 last year, and there has been an even sharper reduction in the number of floats made of Styrofoam, from 131,000 to under 18,000 over the same period.

Even so, some conservationists advocate a more radical solution.

“We need to revolutionize the practice, allowing the ecosystem of the waterways to be restored,” said Tara Buakamsri, Thailand country director for the environmental group Greenpeace. “We should not release any floats, because even if they are made from natural materials, the amount of them exceeds what rivers can naturally deal with.”

“We depend on clean water for our livelihood and the aim of Loy Krathong should be to protect and rejuvenate our rivers without putting anything in them.”

Sales of materials for krathongs have been slow this year due to the pandemic, said Nopparat Tangtonwong, a vendor at Pak Klong market, famous for selling flowers.

“COVID-19 causes the economy to be sluggish, so people prefer saving their money and floating online instead,” she said.

At the same time, children are uninterested in banana-leaf floats, the main natural alternative to Styrofoam, she said. “They prefer fancy floats made of ice-cream cones and bread because they can feed the fish at the same time.”

Such an approach is not helpful, said Wijarn Simachaya, president of Thailand Environment Institute. “If you float somewhere with no fish, those floats will cause pollution in the water. It is difficult to collect them, too, as the bread absorbs the water and sinks into the river. “

“In addition, the sellers usually put chemical colors in those floats, which is harmful to the water,” he said.

Banana leaves are the best krathong material because they do not decompose too quickly, and once collected, can be used for making fertilizer, Wijarn said.

“Doing a virtual Loy Krathong celebration is another good solution to avoid environmental damage, especially during the COVID-19 outbreak, but I don’t think it can satisfy people’s lifestyle, as they still want to enjoy the festival,” he said.

Late Friday night after people floated their cares away, municipal workers come out to scoop up a sea of floats that drifted along canals and down the Chao Phraya River before they decomposed and contaminated the water.

Dozens of small boats traveled along the river, each carrying about half a dozen people with hand-held nets. The boats then took their catch to a moored mothership, where it was dumped into a large shredding machine, compacted and hauled away by garbage trucks for landfill in a waste dump.

“We hope that this year the numbers of krathongs made with Styrofoam will continue to decrease and will be less than last year. And we will finish our cleanup operation before 5 o’clock in the morning,” said Chatree Wattanakhajorn, a top Bangkok official.