title: Cometabolic degradation and inhibition kinetics of 1,2-dichloroethane (1,2-DCA) in suspended-growth nitrifying systems.
abstract: Cometabolic degradation of 1,2-dichloroethane (1,2-DCA) and its inhibitory impact on nitrification were investigated by the use of a mixed suspended-growth culture enriched for nitrifiers. 1,2-DCA was found to be cometabolically degradable by the nitrifier culture. This degradation rate was found to be dependent on the initial 1,2-DCA level. The first-order 1,2-DCA degradation rate constants ranged between 0.42 and 0.87 L (g VSS)(-1) h(-1). Increase in NH4-N utilization favoured cometabolic degradation of 1,2-DCA. The amount of 1,2-DCA degraded per unit mass of NH4-N strongly correlated with initial NH4-N and 1,2-DCA concentrations, ranging between 50 mg L(-1) and 200 mg L(-1) and 1600 microg L(-1) and 100,000 microg L(-1), respectively. The presence of 1,2-DCA caused inhibition of oxygen uptake and NH4-N utilization. In spite of the adverse effect of 1,2-DCA on the nitrifying biomass, the system had a high capacity for cometabolic removal of this compound even at inhibitory concentrations. 1,2-DCA had mainly mixed inhibitor characteristics, but at low concentrations (< 25,000 microg/L) it acted rather as a competitive inhibitor. The inhibition constants belonging to 1,2-DCA, K(ic) (the dissociation constant of the enzyme-inhibitory compound complex) and K(iu) (the dissociation constant of the enzyme-substrate-inhibitory compound complex) were determined to be 6000-8000 microg L(-1) and 188,000-200,000 microg L(-1), respectively.
authors.affiliation: Department of Environmental Engineering, University of Marmara, Kuyubasi, Istanbul, Turkey. bilge.alpaslan@marmara.edu.tr
authors.forename: B Alpaslan
authors.initials: BA
authors.lastname: Kocamemi
authors.forename: F
authors.initials: F
authors.lastname: Ceçen
mesh_terms: D000332:Aerobiosis; D001673:Biodegradation, Environmental; D019149:Bioreactors; D003470:Culture Media / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005025:Ethylene Dichlorides / Q000737:chemistry*; D007700:Kinetics; D009584:Nitrogen / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D015203:Reproducibility of Results; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D003470:Culture Media; D005025:Ethylene Dichlorides; D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; C024565:ethylene dichloride; D009584:Nitrogen; D010100:Oxygen