China treats polluted water at Tianjin blast site

Thousands of tonnes of contaminated water at Tianjin Port, the site of two massive warehouse explosions last week, needs to be treated, over fears that rain may exacerbate the problem.

Pipeline and ground water at the blast site will be processed and drained to make room for the coming rain, said Bao Jingling, Tianjin bureau of environmental protection chief engineer, on Tuesday morning.

He estimates that there is "tens of thousands of tonnes" of contaminated water in the crater created by the blasts.

On Monday, water tested at eight of the area's 40 water monitoring stations was found to contain excessive levels of cyanide, with some samples containing 28.4 times more than the standard, according to Bao.

Bao made the remarks as the northern city experienced light rain on Tuesday morning, stoking concerns that rescue efforts could be disrupted and contamination could spread at the site where hundreds of tonnes of toxic cyanide had been stored.

A dam was built around the 100,000-square-meter core area of the blasts to prevent the outflow of contaminated water should it rain. The cofferdam will be reinforced to prepare for heavy rain, he said.

Air quality is also being closely monitored over fears that rain might set off chemical reactions and release toxic gases, Bao added.

Bao on Tuesday afternoon said that rain that morning had some effect on the air quality. From noon to 2 p.m., only four of the 18 air monitoring stations had detected hydrogen cyanide, with a maximum recorded value of 0.007 milligram per cubic meter, much lower than the national safety standard of 0.024 milligram per cubic meter.

"Cyanide is only harmful when people have direct and long-term contact with it," Bao said. "So it will not affect the health of those staying around the blast site."

The environmental authority may establish more monitoring stations, Bao said, adding that monitoring personnel from other cities and provinces had been despatched to Tianjin.

From today, Tianjin environment monitoring center said it will release air monitoring station data to the public every two hours.

Tianjin maritime department has been tasked with observing all sewage outlets into the sea around Tianjin Port to ensure any contaminated water or waste is reported and dealt with immediately.

A total of 114 people have been confirmed dead, and 57 remain missing after two huge explosions just before midnight on Aug. 12 at a warehouse that held hazardous chemicals.

Officials say that around 700 tonnes of sodium cyanide stored at the blast site remains mostly unaffected.

According to He Shushan, vice mayor of Tianjin, as of Monday night chemical specialists had searched a radius of three kilometers around the blast site's core area. "We have cleaned 150 to 160 tonnes of sodium cyanide."