Removal of Selenate in Simulated Agricultural Drainage Water by a Rice Straw Bioreactor Channel System

Removal of selenium (Se) from agricultural drainage water is important in protecting wetland wildlife. Three flow‐through bioreactor channel systems (BCSs), each with three channels filled with rice ( Oryza sativa L.) straw, were set in the laboratory to determine removal of selenate [Se(VI)] (1020 μg L −1 ) from drainage water with a salinity of 10.4 dS m −1 , a pH of 8.1, and a nitrate NO − 3 range of 0 to 100 mg L −1 Results showed that the rice straw effectively reduced Se(VI) during 122 to 165 d of the experiments. Calculation of Se mass in the three BCSs showed that 89.5 to 91.9% of the input Se(VI) was reduced to red elemental Se [Se(0)], where 96.6 to 98.2% was trapped in the BCSs. Losses of each gram of rice straw were almost equal to the removal of 1.66 mg of Se from the drainage water as a form of red Se(0), indicating that rice straw is a very effective organic source for removing Se(VI) from drainage water.