This capital of northeast China's Heilongjiang Province is racing against time to make sure drinking water will be safe once the supply is resumed.

Workers were installing new filtering material at the city's water plants on Friday. They were replacing anthracite with activated carbon, which can absorb more pollutants. More than 80 People's Liberation Army soldiers joined the work at the No 3 plant, which purifies 80 percent of the city's drinking water.

An 80-kilometer swathe of contaminated water in the Songhua River, which supplies water to the city, was flowing through and expected to leave the urban area before Saturday noon.

The slick, caused by a chemical plant blast on the upper reaches of the river on November 13, forced Harbin to suspend its water supply for four days starting from midnight on Tuesday.

The city now has more than 1,200 tons of active carbon, an amount considered "basically sufficient," the government said on its website. More active carbons will arrive on Saturday from Hebei and Shanxi provinces and Ningxia Hui Autonomous Region, it added.

Wang Minghe, deputy director of the water plant, told the local media that "we are ready to serve once the contaminated water passes."

Also, a work group of the State Council, China's cabinet, left Beijing on Friday for Harbin, a city of 3.8 million people, to investigate the incident.

The State Environmental Protection Administration (SEPA) said on Thursday that a chemical plant of the Jilin Petrochemical Company, under the China National Petroleum Corp, (CNPC) was responsible for the toxic spill.

"The presence of disciplinary officials on the team indicates that punishment of irresponsible acts are on the way," Xinhua said, without elaborating.

On Friday, Harbin resident Ding Ning sued the Jilin plant in Nangang District Court, seeking 15 yuan (US$1.85), the amount he spent on bottled water, and a formal apology, local media reported. CNPC, the parent company, had apologized on Thursday. The court said it would decide on Monday whether to accept the case.

It was estimated that about 100 tons of benzene and nitrobenzene were released into the Songhua River. The pollutants, moving at 2 kilometers an hour, were expected to flow downstream into Russia within a few weeks.

The concentration of nitrobenzene reached its peak at midnight on Thursday at Sifangtai, Harbin's first water inlet. It was 33 times more than the safety level, the Harbin Municipal Environment Bureau said on Friday.

An official with the Ministry of Water Resources said water flow in the Songhua is quite slow, as it is in a dry and frozen season. The ministry has ordered two reservoirs along the Songhua to discharge more water to dilute the pollutants,

The Fengman Hydropower Station in the city of Jilin, in neighboring Jilin Province, was discharging water at 1,000 cubic meters a second, six times its usual volume.

The concentration is expected to fall further as more tributaries join the Songhua downstream from Harbin, said Zhou Linbo, spokesman for the bureau.

There were no cases of residents suffering from poison as a result of water pollution, said Liu Minglie, director of the Harbin Municipal Health Bureau.

"We are checking the newly drilled wells for benzene and nitrobenzene," he said.

To ease public concern over possible contamination in underground water, Liu said that no benzene or nitrobenzene had been found in the wells within one kilometer of the river bank. The health bureau disinfected 435 wells and 124 water tanker vehicles, he said.

Meanwhile, another chemical plant accident hundreds of kilometers away prompted fears of a second benzene leak and warnings to residents not to drink river water, Xinhua said.

The second incident was in Dianjiang, a county in Chongqing Municipality, southwest China, where an explosion at a chemical plant on Thursday killed one worker, Xinhua said.

(China Daily November 26, 2005)