title: Strategies to evaluate biodegradability: application to chlorinated herbicides.
abstract: The biodegradability of nitrochlorinated (diuron and atrazine) and chlorophenoxy herbicides (2,4-D and MCPA) has been studied through several bioassays using different testing times and biomass/substrate ratios. A fast biodegradability test using unacclimated activated sludge yielded no biodegradation of the herbicides in 24 h. The inherent biodegradability test gave degradation percentages of around 20-30% for the nitrochlorinated herbicides and almost complete removal of the chlorophenoxy compounds. Long-term biodegradability assays were performed using sequencing batch reactor (SBR) and sequencing batch membrane bioreactor (SB-MBR). Fixed concentrations of each herbicide below the corresponding EC50 value for activated sludge were used (30 mg L(-1) for diuron and atrazine and 50 mg L(-1) for 2,4-D and MCPA). No signs of herbicide degradation appeared before 35 days in the case of diuron and atrazine and 21 days for 2,4-D, whereas MCPA was partially degraded since the early stages. Around 25-36% degradation of the nitrochlorinated herbicides and 53-77% of the chlorophenoxy ones was achieved after 180 and 135 days, respectively, in SBR, whereas complete disappearance of 2,4-D was reached after 80 days in SB-MBR.
authors.affiliation: Sección Departamental de Ingeniería Química, Universidad Autónoma de Madrid, Carretera Madrid-Colmenar Viejo Km 12.700, 28049, Madrid, Spain, sonia.sanchis@uam.es.
authors.forename: S
authors.initials: S
authors.lastname: Sanchis
authors.forename: A M
authors.initials: AM
authors.lastname: Polo
authors.forename: M
authors.initials: M
authors.lastname: Tobajas
authors.forename: J J
authors.initials: JJ
authors.lastname: Rodriguez
authors.forename: A F
authors.initials: AF
authors.lastname: Mohedano
mesh_terms: D001673:Biodegradation, Environmental; D001681:Biological Assay; D019149:Bioreactors; D006540:Herbicides / Q000737:chemistry* / Q000378:metabolism; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry* / Q000378:metabolism; D012722:Sewage / Q000737:chemistry
chemical_list: D006540:Herbicides; D006843:Hydrocarbons, Chlorinated; D012722:Sewage
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