title: Oxidation-reduction potential as a control variable for the anaerobic stage during anaerobic-aerobic p-nitrophenol degradation.
abstract: Combined anaerobic-aerobic processes are a viable alternative for the treatment of xenobiotic compounds that are difficult to treat by traditional processes. The variable nature of the sequencing batch reactors, SBR, systems allows manipulation of the selective pressure on the microorganisms. Then, the activity of the community can be dynamically adjusted to meet changing effluents conditions. To improve the response of the SBR to changing influent conditions, several efforts have been made to automate and control the duration of the sequential phases of the SBR. The objective of this work is to present and discuss the feasibility of the use of the oxidation-reduction potential, ORP, as a control variable for the determination of the anaerobic phase length in an anaerobic-aerobic SBR used to degrade p-nitrophenol, PNP. The control of the anaerobic phase of the anaerobic-aerobic reactor was achieved with software developed at the Institute of Engineering-UNAM. During the anaerobic stage, the PNP is reduced to p-aminophenol, PAP. As a consequence of the compound transformation, there is a change in the oxidation-reduction potential of the culture medium. This change was used to indicate the minimal concentration of PNP and, as a consequence, the maximal PAP concentration. The feasibility of the algorithm for using the variations in the ORP to determine on-line the length of the anaerobic stage in an anaerobic-aerobic process was demonstrated in our laboratory.
authors.affiliation: Environmental Bioprocesses Department, Institute of Engineering, National University of Mexico, Ap. Postal 70-472, 04510 México D.F., Mexico. gbm@pumas.iingen.unam.mx
authors.forename: Germán
authors.initials: G
authors.lastname: Buitrón
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Betancur
authors.forename: Gloria
authors.initials: G
authors.lastname: Moreno
authors.forename: Jaime A
authors.initials: JA
authors.lastname: Moreno
mesh_terms: D000332:Aerobiosis / Q000502:physiology; D000465:Algorithms; D000693:Anaerobiosis / Q000502:physiology; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D004563:Electrochemistry / Q000379:methods*; D005246:Feedback / Q000502:physiology; D006706:Homeostasis / Q000502:physiology*; D007220:Industrial Waste / Q000517:prevention & control; D009596:Nitrophenols / Q000493:pharmacokinetics*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010865:Pilot Projects; D012984:Software; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics; D018508:Water Purification / Q000379:methods
chemical_list: D007220:Industrial Waste; D009596:Nitrophenols; D014874:Water Pollutants, Chemical; D010100:Oxygen; C024836:4-nitrophenol