Comparison of pyrolucite fixed and fluidized beds for iron and manganese control in groundwater: A pilot-scale study

Iron and manganese removal is a common water treatment goal in groundwater systems. Pilot-scale pyrolucite fixed and fluidized bed contactors were tested in parallel to examine the iron and manganese removal from a natural groundwater which was supplemented with iron and manganese in order to challenge both processes. The results showed that the design of the distributor plate located at the bottom of the pyrolucite fluidized bed (PFB) contactor had crucial impact on the release of particulate manganese from the filter media. Using an optimal distributor plate, the PFB contactor provided effective manganese removal (<0.02 mg/L) at very high hydraulic loading rate (45 m/h). The fixed bed was also effective at 20 m/h. Under elevated iron concentration (0.18 ± 0.02 mg/L), the pyrolucite fixed bed contactor alone provided almost complete iron and manganese removal while requiring frequent backwash of the filter bed (3 d). However, under such condition, the PFB contactor failed to properly control the concentration of iron and manganese below the target limit of 0.02 mg/L as manganese and iron were found to be carried over in the effluent. Further study should address the potential implementation of a cost-effective post-filtration process, downstream of the PFB contactor, which would finalize the removal of iron and manganese from the PFB effluent.