From Fukushima Diary
(Photo) Radioactive sewage sludge storaged at sewage plant. Posted by Fukushima prefectural government.
High level of I-131 was measured for 11 days this January in dry sewage sludge, Fukushima prefectural government announced on 2/26/2016.
According to the prefectural government, the sewage plant is in Da-te District of Fukushima prefecture.
The highest density was 648.1 Bq/Kg. It was continuously detected from 1/21 to 1/31/2016. The data of February has not been published yet.
Along with I-131, Cs-134/137 density also increase and became the highest, which was 111 Bq/Kg on the same day when I-131 density became the highest.
Both of the highest densities were detected about 1 week after the rain (57.0 mm) to strongly implies the possibility that the discharged radioactive material is carried by the wind and fall with rain.