ABSTRACT
This chapter shows that iron surfaces were effective in reducing Cr(VI) to Cr(III) under typical reducing conditions (pH 2.0 to 3.0). It examines the use of scrap iron filings to treat Cr(VI)-containing metal plating wastewaters. The kinetics of iron particle reaction with Cr(VI) and O2 as well as the settling characteristics and specific resistances of the sludge produced by the process have been evaluated for comparison to conventional treatment schemes. One major objective of the process was to reduce the amount of total iron introduced as a result of the treatment scheme and significantly reduce the sludge production compared to ferrous sulfate reduction. The chemical costs for Cr(VI) reduction using the process are substantially lower than conventional reducing agents. The rates of Cr(VI) reduction and O2 reaction were studied in completely-mixed batch reactors. A bench-scale system was then designed as a continuous flow completely-mixed process in order to evaluate the effectiveness of the iron particles during continuous operation.
