title: Evaluation of hexavalent chromium removal in a continuous biological filter with the use of central composite design (CCD).
abstract: Hexavalent chromium is frequently found in industrial effluents as a result of the industrial applications of this compound and its anti-corrosive features. However, hexavalent chromium is extremely toxic, and its discharge in water is regulated, with a maximum limit of 0.1 mg/L in accordance with legislation established by CONAMA-Brazil (no. 397, April 3, 2008). To achieve lower discharge values, it is necessary to reduce from Cr(VI) to Cr(III), which is less toxic, and an economic alternative involves biological removal of this compound. Residence time distributions (RTDs) were measured to evaluate the behavior of actual biofilter operation conditions in a biofilter flow. The medium residence time distributions used were 8 and 24 h (recommended by the legislation). To optimize this process, a central composite design was used, considering the initial chromium concentration and pH as the independent variables and the removal of hexavalent chromium as the response. The boundary curves and surface response showed optimal behavior at 3.94 mg/L [Cr(0)] and a pH of 6.2. The removal process of hexavalent chromium is mathematically described by the Michaelis-Menten kinetic model. This model appropriately represents the variation of chromium concentration along the bioreactor.
authors.affiliation: Faculty of Chemical Engineering, Uberlândia Federal University, P.O. Box 593, Av. João Naves de Ávila, 2121, Campus Santa Mônica, Bloco 1K 38400-902, Uberlândia, MG, Brazil.
authors.forename: Maurielem Guterres
authors.initials: MG
authors.lastname: Dalcin
authors.forename: Marcelo Melo
authors.initials: MM
authors.lastname: Pirete
authors.forename: Diego Andrade
authors.initials: DA
authors.lastname: Lemos
authors.forename: Eloizio Júlio
authors.initials: EJ
authors.lastname: Ribeiro
authors.forename: Vicelma Luiz
authors.initials: VL
authors.lastname: Cardoso
authors.forename: Miriam Maria
authors.initials: MM
authors.lastname: de Resende
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D002857:Chromium / Q000737:chemistry*; D005374:Filtration / Q000379:methods*; D008962:Models, Theoretical; D012044:Regression Analysis; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion