Iron and manganese removal by using manganese ore constructed wetlands in the reclamation of steel wastewater.
To reclaim treated steel wastewater as cooling water, manganese ore constructed wetland was proposed in this study for the removal of iron and manganese. In lab-scale wetlands, the performance of manganese ore wetland was found to be more stable and excellent than that of conventional gravel constructed wetland. The iron and manganese concentration in the former was below 0.05 mg/L at hydraulic retention time of 2-5 days when their influent concentrations were in the range of 0.16-2.24 mg/L and 0.11-2.23 mg/L, respectively. Moreover, its removals for COD, turbidity, ammonia nitrogen and total phosphorus were 55%, 90%, 67% and 93%, respectively, superior to the corresponding removals in the gravel wetland (31%, 86%, 58% and 78%, respectively). The good performance of manganese ore was ascribed to the enhanced biological manganese removal with the aid of manganese oxide surface and the smaller size of the medium. The presence of biological manganese oxidation was proven by the facts of good manganese removal in wetlands at chemical unfavorable conditions (such as ORP and pH) and the isolation of manganese oxidizing strains from the wetlands. Similar iron and manganese removal was later observed in a pilot-scale gravel-manganese-ore constructed wetland, even though the manganese ore portion in total volume was reduced from 100% (in the lab-scale) to only 4% (in the pilot-scale) for the sake of cost-saving. The quality of the polished wastewater not only satisfied the requirement for cooling water but also suitable as make-up water for other purposes.
Xu
Jing-Cheng
JC
College of Environmental Science & Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 20092, China.
Chen
Gu
G
Huang
Xiang-Feng
XF
Li
Guang-Ming
GM
Liu
Jia
J
Yang
Na
N
Gao
Sai-Nan
SN
D003247:Conservation of Natural Resources; D007220:Industrial Waste / Q000517:prevention & control; D007501:Iron / Q000302:isolation & purification; D008345:Manganese / Q000302:isolation & purification; D019216:Metals, Heavy / Q000302:isolation & purification*; D010865:Pilot Projects; D013232:Steel; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
D007220:Industrial Waste; D019216:Metals, Heavy; D013232:Steel; D008345:Manganese; D007501:Iron