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Item Biological Treatment of 3,6-Dichloro-2-Methoxybenzoic Acid Using Anaerobic-Aerobic Sequential Batch Reactor(Springer Basel info@birkhauser-science.com, 2019) Mahesh, G.B.; Manu, B.A sequential anaerobic-aerobic batch reactor was used to treat 3,6-dichloro-2-methoxybenzoic acid (dicamba) during a long operation period of 340 days in the presence of disodium anthraquinone-2,6-disulphonate (AQS) as redox mediator. The sludge activity was evaluated for different dosages of dicamba over constant hydraulic retention time (HRT), neutral pH (6.5–7.5) and at ambient reactor temperature. Effects of increased dicamba concentration, solids retention time (SRT) and oxidation reduction potential (ORP) on the biodegradation of dicamba was monitored and compared with control reactor containing no dicamba. Results revealed that long operation period, long SRT and ORP were playing important role in the breakdown of dicamba to its transformation products and subsequent removal in the system. The system was capable of degrading the compound completely during long operation period, long SRT and at low ORP in the presence of AQS. Reducing condition in the anaerobic reactor significantly contributed to the treatment process through demethylation, dehalogenation and dechlorination reactions in the presence of different reducing bacteria. The results of GC-HRMS identified the anaerobic transformation products of dicamba as oleic acid (C18H34O2), 9-Octadecenoic acid (Z), 2-hydroxy-1-(hydroxymethyl)ethyl ester (C21H40O4), trans-13-Ocatadecenoic acid (C18H34O2) compounds which were then oxidised in the aerobic reactor. © 2019, Springer Nature Switzerland AG.Item Biodegradation of ametryn and dicamba in a sequential anaerobic-aerobic batch reactor: A case study(IWA Publishing 12 Caxton Street London SW1H 0QS, 2019) Mahesh, G.B.; Manu, B.Agricultural runoff often contains persistent halogenated herbicide compounds like 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryn) and 3,6-dichloro-2-methoxybenzoic acid (dicamba). These can enter the food chain through drinking water, causing serious effects for people and the environment. A sequential anaerobic reactor followed by an aerobic reactor was operated and investigated for herbicide removal efficiency at constant, three-day, hydraulic retention time (HRT) and organic loading rate (OLR) of 0.2025 kg-COD/m3/d. The effect of the herbicides on anaerobic bacteria was evaluated based on total biogas production and bacterial activity, which indicated that there was no inhibition on the acclimated biomass. The sequential reactor pair removed 72% of ametryn and 78% dicamba, with COD removal efficiencies of 86% and 85% respectively. The different high-performance liquid chromatography (HPLC) peaks indicate that the compounds are biotransformed and this was confirmed by gas chromatograph high resolution mass spectrometry (GC-HRMS). © IWA Publishing 2019.