Biodegradation of agricultural herbicides in sequencing batch reactors under aerobic or anaerobic conditions

• Published in: Water research (Oxford) 2008-06, Vol.42 (12), p.3218-3224
• Main Authors: Celis, E., Elefsiniotis, P., Singhal, N.
• Format: Article
• Language: English
• Subjects: 2,4-D; 2,4-Dichlorophenoxyacetic Acid - chemistry; 2,4-Dichlorophenoxyacetic Acid - metabolism; 4-D; activated sludge; aerobic conditions; Aerobic/anaerobic treatment; Aerobiosis; anaerobic conditions; anaerobic digesters; anaerobic digestion; Anaerobiosis; Applied sciences; Biodegradation; Biodegradation, Environmental; biomass; Bioreactors; carbon; Exact sciences and technology; glucose; Glucose - metabolism; Herbicides; Herbicides - chemistry; Herbicides - metabolism; Isoproturon; Kinetics; Other industrial wastes. Sewage sludge; Oxygen - metabolism; Phenylurea Compounds - chemistry; Phenylurea Compounds - metabolism; Pollution; Sequencing batch reactors; temperature; Wastes; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2008.04.008

This study investigated the biodegradability of the herbicides isoproturon and 2,4-dichlorophenoxyacetic acid (2,4-D) in sequencing batch reactors (SBRs). Two laboratory-scale (2 L liquid volume) SBRs were employed: one reactor performing under aerobic and the other under anaerobic conditions. The aerobic SBR was operated at an ambient temperature (22±2 °C), while the anaerobic SBR was run in the lower mesophilic range (30±2 °C). Each bioreactor was seeded with a 3:1 mixture (by weight) of fresh sludge and biomass that had been previously exposed to both herbicides. The effect of herbicide concentration on either treatment process was explored at a hydraulic retention time (HRT) of 48 h, using glucose as a supplemental carbon substrate. Although no isoproturon degradation was observed in either system during the study, complete 2,4-D removal occurred after an acclimation period of approximately 30 d (aerobic SBR) and 70 d (anaerobic SBR). The aerobic reactor achieved complete 2,4-D utilization at feed concentrations up to 500 mg/L. A further increase to 700 mg/L, however, proved to be inhibitory since 2,4-D biodegradation was negligible. On the other hand, the anaerobic SBR was able to degrade 120 mg/L of 2,4-D, which corresponds to 40% of the maximum feed concentration applied. Moreover, glucose was consumed first throughout the experiment in a sequential utilization pattern relating to 2,4-D, with biodegradation of both substrates following closely first-order kinetics.