Chemical Engineering Journal 181–182 (2012) 144–151 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal jo u r n al hom epage: www.elsevier.com/locate/cej Biodegradation of a mixture of 2,4-dichlorophenoxyacetic acid and multiple chlorophenols by aerobic granules cultivated through plasmid pJP4 mediated bioaugmentation Jing-yun Ma, Xiang-chun Quan ∗ , Zhi-feng Yang, An-jie Li Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China a r t i c l e i n f o Article history: Received 31 July 2011 Received in revised form 6 November 2011 Accepted 11 November 2011 Keywords: Aerobic granule 2,4-Dichlorophenoxyacetic acid Chlorophenol Biodegradation Bioaugmentation a b s t r a c t 2,4-Dichlorophenoxyacetic acid (2,4-D) degrading aerobic granular sludge, obtained through plasmid pJP4 mediated bioaugmentation, was used for the degradation of a mixture of 2,4-D, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) in a sequencing batch reac- tor. The removal rate of 2,4-D always stabilized at above 99%, indicating that the granules were still active in the presence of chlorophenols. The 2,4-D fed granules demonstrated a faster adaptation and higher degradation ability to 4-CP and 2,4-DCP than to 2,4,6-TCP. Nearly complete removals of 2,4-D and chlorophenols were achieved at the initial concentrations of approximately 400 mg/L of 2,4-D, 45 mg/L of 4-CP, 25 mg/L of 2,4-DCP, and 20 mg/L of 2,4,6-TCP and a hydraulic retention time (HRT) of 6 h. Each chlorophenol could be biodegraded and mineralized by the granules as the sole carbon source and the biodegradation followed Haldane inhibition model. The granules maintained a good settling ability and a dominant granular morphology as evidenced by the low sludge volume index (SVI) value (20–70 mL/g) and large granule size (400–610 m) during the long-term operation (420 days). The finally obtained granules showed a different microbial community compared to the granule seeds, and were mainly composed of Novosphingobium sp., Aquincola tertiaricarbonis, Xanthomonas sp. and Pseudorhodoferax caeni. © 2011 Elsevier B.V. All rights reserved. 1. Introduction 2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most commonly used phenoxy acid herbicides in agriculture and hor- ticulture, and chlorophenols are used as raw materials for the production of 2,4-D and its derivatives [1]. Some chlorophenols like 2,4-dichlorophenol (2,4-DCP) and monochlorophenol have been found to be produced as by-products during the biodegradation of 2,4-D [2,3]. Therefore, 2,4-D and chlorophenols may co-exist in Abbreviations: 2,4-D, 2,4-dichlorophenoxyacetic acid; COD, chemical oxygen demand; CP, chlorophenol; DCP, dichlorophenol; DGGE, denaturing gradient gel electrophoresis; EPS, extracellular polymeric substances; ETBE, ethyl tert-butyl ether; HPLC, high performance liquid chromatography; HRT, hydraulic retention time; Ki, inhibition constant; Ks, half-saturation constant; MLSS, mixed liquor suspended solids; MLVSS, mixed liquid volatile suspended solids; MTBE, methyl tert-butyl ether; PBS, phosphate buffered saline; PCP, pentachlorophenol; PCR, polymerase chain reaction; SBR, sequencing batch reactor; SEM, scanning elec- tron microscope; SVI, sludge volume index; TAME, tert-amyl methyl ether; TCP, trichlorophenol; TeCP, tetrachlorophenol; TOC, total organic carbon; V, specific degradation rate; Vmax, maximum specific degradation rate. ∗ Corresponding author. Tel.: +86 10 58802374; fax: +86 10 58802374. E-mail address: xchquan@bnu.edu.cn (X.-c. Quan). polluted water environment or in wastewater discharged from the plants manufacturing herbicides and pesticides. Due to their high toxicity, recalcitrance, as well as suspected carcinogenic and muta- genic impacts, the presence of 2,4-D and chlorophenol residues in environment has created potential risks from both human and natural environment perspectives [4]. Removals of these pollu- tants from wastewater or natural environment using biological methods have attracted more attention than physical and chem- ical methods because of their high efficiency and low costs [5,6]. Various biotechnologies and bioreactors have been applied in treat- ing chlorophenols containing wastewater, such as biofilm reactors, microbial immobilization, special culture bioaugmentation [7–11]. Most of the previous studies focused on the enhancement of biomass and bioactivity in bioreactors. Aerobic sludge granulation, as a novel biotechnology, has attracted significant attention in recent years due to its advan- tages like good sludge settling ability, high biomass retention, as well as resistance to toxic compounds [12–14]. Hence, it is expected to be a promising technology for the degradation of recalcitrant pollutants. Cultivation of aerobic granules capable of degrading inhibitory compounds is more difficult than cultiva- tion of granules degrading easily degradable compounds. To date, just a few researchers have reported the successful cultivation of 1385-8947/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2011.11.041