210,000 households in Japan lost their water supply over the weekend when formaldehyde was found in the Tone River.
The Tone River is a major source of water for many cities along its 193 mile course. When water treatment plants detected formaldehyde in their intake, they shut down the water filtration. The contaminated water was not passed on to households.
Residents had to wait in lines at trucks that brought water in from uncontaminated areas.
The acceptable limit of formaldehyde is 0.080 mg per liter. On Friday, a filtration plant in Saitama detected 0.200 mg per liter. Concentrations of formaldehyde have receded and some water treatment plants along the river have returned to using the water.
A factory spill is suspected, but no cause has been found yet.
Formaldehyde is only the most recent contaminant found in the river. In April 2012, silver crucian carp caught in the Tone River had radioactive cesium concentrations of 110 becquerels per kg. Several fisheries were asked to stop shipments of fish caught in the Tone. The Tone River is 110 miles from the Fukushima Daiichi Plant.
Tone River photo via Creative Commons