Simultaneous Biodegradation and Detoxification of the Herbicides 2,4-Dichlorophenoxyacetic Acid and 4-Chloro-2-Methylphenoxyacetic Acid in a Continuous Biofilm Reactor

• Published in: Water, air, and soil pollution Vol. 228; no. 8; p. 1
• Main Authors: González, Ana Julieta, Fortunato, María Susana, Gallego, Alfredo, Korol, Sonia Edith
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.08.2017; Springer; Springer Nature B.V
• Subjects: 2,4-D; Agricultural chemicals industry; Agricultural practices; Agrochemicals; Atmospheric Protection/Air Quality Control/Air Pollution; Auxins; Bacteria; Batch reactors; Biodegradation; Biofilms; Bioreactors; Chemical oxygen demand; Climate Change/Climate Change Impacts; Contamination; Detoxification; Dichlorophenoxyacetic acid; Earth and Environmental Science; Effluents; Environment; Environmental monitoring; Gas chromatography; Growth regulators; Herbicides; Hydrogeology; Industry; Influents; Lactuca sativa; Microbiological strains; Reactors; Removal; Seeds; Soil Science & Conservation; Spectrophotometry; Surface water; Test organisms; Toxicity; Ultraviolet radiation; Water pollution; Water Quality/Water Pollution; 2,4-d Herbicide mixtures; MCPA; Continuous reactors; Detoxification
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-017-3468-4

The herbicides 2,4-diclorophenoxiacetic and 4-chloro-2-methylphenoxyacetic acids (2,4-D and MCPA) are widely used in agricultural practices worldwide. Not only are these practices responsible of surface waters contamination, but also agrochemical industries through the discharge of their liquid effluents. In this investigation, the ability of a 2,4-D degrading Delftia sp. strain to degrade the related compound MCPA and a mixture of both herbicides was assessed in batch reactors. The strain was also employed to remove and detoxify both herbicides from a synthetic effluent in a continuous reactor. Batch experiments were conducted in a 2-L aerobic microfermentor, at 28 °C. Continuous experiments were carried out in an aerobic downflow fixed-bed reactor. Bacterial growth was evaluated by the plate count method. Degradation of the compounds was evaluated by UV spectrophotometry, gas chromatography (GC), and chemical oxygen demand (COD). Toxicity was assessed before and after the continuous process by using Lactuca sativa seeds as test organisms. Delftia sp. was able to degrade 100 mg L −1 of MCPA in 52 h. When the biodegradation assay was carried out with a mixture of 100 mg L −1 of each herbicide, the process was accomplished in 56 h. In the continuous reactor, the strain showed high efficiency in the simultaneous removal of 100 mg L −1 of each herbicide. Removals of 99.7, 99.5, and 95.0% were achieved for 2,4-D, MCPA, and COD, respectively. Samples from the influent of the continuous reactor showed high toxicity levels for Lactuca sativa seeds, while toxicity was not detected after the continuous process.