The city announced the latest survey of radioactive materials in sewer sludge in a sewage treatment center in the city, and it shows iodine-131 being detected in the sludge cake since August 25.
From the city's announcement on September 7 (original in Japanese, I translated the dates, etc.; emphasis is mine):
Collection date | Testing date | I-131 | Cs-134 | Cs-137 | Cs-Total |
| 7/7/2011 | 7/14/2011 | ND | 81 | 100 | 181 |
| 7/21/2011 | 7/23/2011 | ND | 71 | 64 | 135 |
| 7/28/2011 | 7/30/2011 | ND | 58 | 79 | 137 |
| 8/4/2011 | 8/7/2011 | ND | 38 | 76 | 114 |
| 8/11/2011 | 8/12/2011 | ND | 33 | 52 | 85 |
| 8/25/2011 | 8/27/2011 | 2,300 | 47 | 52 | 99 |
| 8/31/2011 | 9/2/2011 | 590 | 20 | 57 | 77 |
| 9/6/2011 | 9/6/2011 | 480 | 82 | 96 | 178 |
The city says it has stopped the shipment of sludge cakes from this plant because of the high radioactive iodine concentration detected from the August 25 sample, but that the sludge cakes have been used as fertilizer material because the amount of radioactive cesium has been below the provisional safety limit for composts and manures (400 becquerels/kg).