China oil leak affects water for millions

Water supply in the city of Lanzhou, China has been affected by high levels of benzene. Around 2.4 million people across the city have had their tap water affected as a result of an oil leak. While three of the four affected areas of the city have now resumed water supplies, the full extent of the damage is not yet known.

Lanzhou Petrochemical - a subsidiary of China National Petroleum Corporation (CNPC), China's largest oil company - has been blamed for an oil leak that occurred on Friday (April 11th). Crude oil spilled from a pipeline, causing contamination of a water source that is used by a local water plant. This resulted in high levels of benzene making its way into the tap water supply for the city, according to an environmental official while on a conference call with the city government.

An investigation revealed that crude oil had leaked into the soil along a duct that runs between two water works, both owned by Veolia Water. The oil pipeline runs under this ditch, which carries water to the No.1 and No.2 water plant. The break in the pipeline that caused the leak had reportedly been located by Saturday (April 12th), with repairs starting once it had been found.

The high levels of benzene in tap water were reported on Friday morning (local time), prompting the city government to advise residents to avoid drinking tap water for at least 24 hours. In five-out-of-six of the city's water monitoring stations, the levels of benzene measured in tap water was deemed to be safe late Saturday morning. The levels ranged from zero to 6.66 micrograms per litre. 

At the sixth water monitoring point, benzene levels were still being recorded at 35.15 micrograms per litre, exceeding the national limit of ten micrograms per litre. Work is ongoing to return the water at this site to its usual quality, following on from the water works spending Friday night washing the filter system repeatedly and continuously water cycling in an effort to clean the pipeline thoroughly.