Microbial culture dynamics and chromium (VI) removal in packed-column microcosm reactors

摘要

Microbial Cr(VI) reduction in groundwater aquifer media was investigated in microcosm reactorsnextracted from Cr(VI) contaminated sites in South Africa. The reactors were operated under anninfluent Cr(VI) concentration of 40mg/L to simulate the current Cr(VI) level at the contaminatednsite. Near complete Cr(VI) removal was observed in microcosm reactors inoculated with Cr(VI)nreducing bacteria from dried activated sludge collected from a treatment plant receiving periodicnloadings of Cr(VI). The best performance was observed under low hydraulic loading (flow rate,nQ ¼ 0.310 cm3n/hr). Microbial culture characterisation results showed a change in culturencomposition after 17 days of reactor operation, indicating Bacillus and Lysinibacillus species asnthe most dominant organisms in reactors that reduced Cr(VI). The predominance of Bacillus andnLysinibacillus species was either due to resilience against toxicity or adaptation to the changingnconditions in the reactor. This research was the initial step towards the development of an in situnbioremediation process to contain the spread of a Cr(VI) plume in a groundwater aquifer atncontaminated site in Brits, South Africa. South Africa holds about 72% percent of the world’snchromium resources, the majority of which is mined in the North Eastern region of the countrynformally known as Transvaal.