Biodegradation of 2,4-dicholophenoxyacetic acid using an acidogenic anaerobic sequencing batch reactor

Abstract

A bench-scale study was carried out to investigate the potential to biologically treat 2,4-dicholophenoxyacetic acid (2,4-D) contaminated wastewater in an anaerobic sequencing batch reactor (ASBR), operated in the acid-phase digestion mode. The effects of 2,4-D feed concentration (20 to 200 mg L −1 ) and temperature (ambient and 33 • C) on biodegradation were investigated at a hydraulic retention time of 48 h and a solids retention time of 10 d, using glucose as a supplemental substrate. Following a long acclimation period of about 100 d, complete 2,4-D degradation was observed at feed concentrations of 20 and 100 mg L −1 . However, at a 2,4-D concentration of 200 mg L −1 , only 65% removal was achieved. Overall, operation at an ambient temperature resulted in a slightly better performance than that at 33 • C. An adaptation period of approximately a week was required any time the 2,4-D concentration was increased, indicating a sensitive behavior towards shock loadings. On the other hand, glucose was completely and readily degraded throughout the study. A sequential utilization pattern of glucose and 2,4-D was also observed, with degradation of both substrates following first-order kinetics. Moreover, volatile fatty acids (VFAs) were the main products of acidogenesis, accounting for 65% of the effluent soluble chemical oxygen demand (COD), with acetic acid being by far the most predominant VFA detected.Résumé : Une étude en laboratoire a été effectuée afin d'examiner le potentiel de traitement biologique de l'acide (2,4-dichlorophénoxy)acétique (2,4-D) contaminant les eaux usées contenues dans un réacteur à séquençage discontinu anaérobie (ASBR) fonctionnant en mode de digestion en phase acide. Les effets de la concentration de l'alimentation en 2,4-D (de 20 à 200 mg L −1 ) et de la température (ambiante et 33 • C) sur la biodégradation ont été étudiés pour un temps de rétention hydraulique de 48 heures et un temps de rétention des matières solides de 10 jours, en utilisant le glucose comme substrat supplémentaire. Après une longue période d'acclimatation d'environ 100 jours, la dégradation totale du 2,4-D a été atteinte à des concentrations d'alimentation de 20 et de 100 mg L −1 . Cependant, à une concentration de 2,4-D de 200 mg L −1 , la dégradation n'atteignait que 65 %. Règle générale, l'opération à température ambiante a engendré un rendement légèrement meilleur qu'à 33˚C. Une période d'adaptation d'environ une semaine était requise à chaque fois que la concentration en 2,4-D était augmentée, indiquant ainsi une sensibilité aux surcharges. Mais le glucose a été complètement et rapidement dégradé durant toute l'étude. Un patron d'utilisation séquentiel du glucose et du 2,4-D a été observé, la dégradation de ces deux substrats suivant une cinétique du premier ordre. De plus, les acides gras volatils (ACV) constituaient les principaux produits de l'acidogénèse comptant pour 65 % de la demande chimique en oxygène (DCO) soluble de l'effluent, l'acide acétique étant de loin l'ACV le plus prédominant.

Biodegradation of industrial-strength 2,4-dichlorophenoxyacetic acid wastewaters in the presence of glucose in aerobic and anaerobic sequencing batch reactors

“…It should be noted that the presence of a readily biodegradable carbon source such as glucose is crucial during the long acclimation periods mentioned above in order to provide the carbon required for heterotrophic bacterial growth. Furthermore, the addition of supplementary carbon sources in continuously-operated systems treating a potentially toxic substrate has been found to be beneficial in sustaining a reasonable amount of biomass in the reactors, which enhances the operational stability and improves the performance of the treatment process [15,17].…”

“…As a result, the sequencing batch reactor (SBR) technology has recently become an alternative option to traditional activated sludge systems for the treatment of recalcitrant compounds [15,16]. More specifically (and despite having been shown to be amenable to the processing of 2,4-D [17,18]); no comprehensive study has systematically examined the ability of SBRs to accommodate the limits of industrial strength concentrations, particularly under both aerobic and anaerobic conditions.…”

Treatment of Four Industrial Wastewaters by Sequencing Batch Reactors: Evaluation of Cod, TKN and Tp Removal

“…The ability of properly acclimated biomass to degrade non-readily biodegradable compounds has been well documented in the literature [3,20]. The reactors were, therefore, started with a liquid volume of 5 l (i.e.…”

“…It is ideal for treating industrial wastes because of its intrinsic ability to keep biomass in the system for extended periods of time. Additional benefits of SBRs include the ease of operation, the significant space savings arising from all reactions contained in one tank, the tolerance to shock loadings and the ability to adapt to new process control technologies [3,4]. In this paper, SBRs will be briefly mentioned in the context of four specific wastewaters that are significant issues from the Thai perspective.…”

Effects of combined growth of biogenic and xenobiotic substrates on degradation of xenobiotic by activated sludge

“…The uncoupling, or the energy-spilling reactions, occurs when catabolism energy is dissipated or diverted away from anabolism through the metabolism of a substrate in bacterial cells [1]. Although xenobiotics containing wastewater can be suitably treated using biological methods [2,3,4,5], the xenobiotic nature of the pollutant requires the treatment plant microorganisms (typically activated sludge) to go through an acclimation phase before the microorganisms evolve the degradation capability for treating the influent xenobiotics. Thus, biodegradation method is used widely to treat xenobiotics in water treatment methods.…”