In a wastewater treatment plant (WWTP) in Kohriyama, Fukushima, high radioactivity sludge was found, 26,400 Bq/kg in sewage sludge, and 334,000 Bq/kg in molten slag, which is more than 1,000 times of 246 Bq/kg in molten slag before the nuclear plant accident. There are combined collection and separate collection systems in the sewer collection systems. The former is to collect both wastewater and rain water, and the latter is to collect only wastewater and rain water is discharged to ambient water without collection. Disaster Provision Main Office of Fukushima Prefecture said they will conduct monitoring on other WWTPs in the prefecture firstly for WWTPs with the combined collection systems and later for those with the separate collection systems.

1 May 2011: Ministry of Land, Infrastructure, Transportation and Tourism (MLIT) of Japan, Radioactivity of sewage sludge at the Ken-naka Wastewater Treatment Plant (WWTP)

1 May 2011: Disaster Provision Main Office of Fukushima Prefecture, Radioactivity of sewage sludge at the Ken-naka Wastewater Treatment Plant (WWTP)

Media reports

The followings are some information on radioactivity in sewage sludge on the web. Most of them are from the USA in the 1990s.