Water Research 121 (2017) 338e348 Contents lists available at ScienceDirect Water Research journal homepage: www.elsevier.com/locate/watres Biotransformation of nitrogen- and sulfur-containing pollutants during coking wastewater treatment: Correspondence of performance to microbial community functional structure * Dev Raj Joshi a, b, Yu Zhang a, b, , Yinxin Gao a, b, Yuan Liu a, Min Yang a, b a State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China b University of Chinese Academy of Sciences, Beijing, 100049, China article info abstract Article history: Although coking wastewater is generally considered to contain high concentration of nitrogen- and Received 13 March 2017 sulfur-containing pollutants, the biotransformation processes of these compounds have not been well Received in revised form understood. Herein, a high throughput functional gene array (GeoChip 5.0) in combination with Illumina 18 May 2017 MiSeq sequencing of the 16S rRNA gene were used to identify microbial functional traits and their role in Accepted 21 May 2017 biotransformation of nitrogen- and sulfur-containing compounds in a bench-scale aerobic coking Available online 24 May 2017 wastewater treatment system operated for 488 days. Biotransformation of nitrogen and sulfur- containing pollutants deteriorated when pH of the bioreactor was increased to >8.0, and the microbial Keywords: fi < Coking wastewater community functional structure was signi cantly associated with pH (Mantels test, P 0.05). The release Nitrogen and sulfur containing organic of ammonia nitrogen and sulfate was correlated with both the taxonomic and functional microbial compound community structure (P < 0.05). Considering the abundance and correlation with the release of ammonia Functional gene nitrogen and sulfate, aromatic dioxygenases (e.g. xylXY, nagG), nitrilases (e.g. nhh, nitrilase), dibenzo- Taxa-function relationship thiophene oxidase (DbtAc), and thiocyanate hydrolase (scnABC) were important functional genes for Microbial network biotransformation of nitrogen- and sulfur-containing pollutants. Functional characterization of taxa and network analysis suggested that Burkholderiales, Actinomycetales, Rhizobiales, Pseudomonadales, and Hydrogenophiliales (Thiobacillus) were key functional taxa. Variance partitioning analysis showed that pH and influent ammonia nitrogen jointly explained 25.9% and 35.5% of variation in organic pollutant degrading genes and microbial community structure, respectively. This study revealed a linkage between microbial community functional structure and the likely biotransformation of nitrogen- and sulfur- containing pollutants, along with a suitable range of pH (7.0e7.5) for stability of the biological system treating coking wastewater. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Increasing environmental awareness coupled with more stringent standards has triggered various industries to challenge themselves Coking wastewater is liquid waste from coke production laden in seeking appropriate wastewater treatment technologies (Teh with numerous pollutants, including phenols, polyaromatic hy- et al., 2016). drocarbons, nitrogen-, sulfur- and oxygen-containing heterocyclics, Biological treatment of coking wastewater has long been of and acyclic compounds (Liu et al., 2017; Sharma and Philip, 2016; interest for environmental engineering studies. Most of the Zhang et al., 1998), and can induce toxic and carcinogenic impacts identified compounds, including phenols, thiocyanates, cyanides, (Dehua et al., 2016; Zhao et al., 2014) on the environment. and polyaromatic hydrocarbons, can be biologically removed (Bai et al., 2011; Jeong and Chung, 2006; Li et al., 2003). Recent pyrosequencing analysis has shown that microbial genera, such as Thiobacillus, Comamonas, Pseudomonas, Thaurea, Burkholderia, * Corresponding author. State Key Laboratory of Environmental Aquatic Chem- istry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sci- and Trichosporon, might play an important role in the degrada- ences, Beijing, 100085, China. tion of phenols, thiocyanates, and cyanides in coking wastewater E-mail address: [email protected] (Y. Zhang). http://dx.doi.org/10.1016/j.watres.2017.05.045 0043-1354/© 2017 Elsevier Ltd. All rights reserved. D.R. Joshi et al. / Water Research 121 (2017) 338e348 339 (Joshi et al., 2016; Ma et al., 2015a; Zhu et al., 2016). However, of 488 days, with a focus on the deamination and desulfurization system performance instability or sudden failures of full-scale processes. Except for the removal of COD and total phenols, pa- applications treating coking wastewater have also been re- rameters describing the release of ammonia and sulfate with ported (Kim et al., 2009; Vazquez et al., 2006b). The presence of respect to influent COD were used for the evaluation of waste- toxic compounds like phenols and cyanides is often speculated as water treatment performance. Sludge samples from different the main reason for the deterioration of treatment performance temporal points during the operation period were taken for phy- (Amor et al., 2005; Sharma and Philip, 2014). Judging from the logenic and functional gene community analysis using Illumina high biodegradability of these pollutants (Feng et al., 2015; MiSeq sequencing of 16S rRNA genes and functional gene micro- Marrot et al., 2006; Papadimitriou et al., 2009), however, it is array (GeoChip 5.0), respectively. GeoChip 5.0 contains 167,044 assumed that some as yet unknown compounds might be more distinct probes, covering 395,894 coding sequences from 1593 sensitive to environmental conditions and thus cause process functional gene families involved in microbial biogeochemical failure. cycling and organic remediation (http://ieg.ou.edu/), and has been On the other hand, excessive ammonium and sulfate can be extensively employed to analyze the functional gene structure of generated during biological treatment of coking wastewater (Joshi microbial communities in different environments (Chan et al., et al., 2016; Staib and Lant, 2007; Vazquez et al., 2006a), sug- 2013; Zhang et al., 2013b). The functional traits of abundant mi- gesting possible biodegradation of nitrogen- and sulfur-containing crobial taxa were identified by assigning taxa to functional gene organic and inorganic compounds. Based on the low chemical categories involved in the degradation of organic pollutants, as oxygen demand to total organic carbon (COD/TOC) ratio (Lim et al., described in GeoChip 5.0 (Chan et al., 2013). Potential bacterial 2003), refractory organic compounds including nitrogen- and hosts and functional genes associated with the biotransformation sulfur-containing compounds (Huang et al., 2016; Zhang et al., of organic pollutants, particularly those containing nitrogen or 2013a), may represent a substantial fraction as only nitrogenous sulfur, were further explored by network analysis based on the compounds constitute approximately 20e40% of the organic GeoChip and MiSeq data. Lastly, the contributions of wastewater component in coking wastewater (Li et al., 2003; Meng et al., variables to the microbial community and functional structures 2016). Indeed, nitrogen and sulfur-containing compounds are of were analyzed by variation partitioning analysis (VPA). This study great environmental importance due to their high toxicity and could advance our understanding of biological treatment pro- persistence (Dehua et al., 2016; Jensen et al., 2003) and hence cesses of coking wastewater, and improve the optimization of might be critical for the treatment of coking wastewater. So un- system operation. derstanding the functional ecology of biotransformation of these pollutants during the treatment process has great practical sig- nificance. Biodegradation of nitrogen and sulfur heterocycles via 2. Materials and methods deamination and desulfurization pathways by several bacterial isolates including Pseudomonas, Burkholderia, Rhodococcus, Sphin- 2.1. Coking wastewater treatment and sludge sample collection gomonas, Comamonas (Gai et al., 2007; Jiang et al., 2016; Tao et al., 2011) and thiocyanates via carbonyl pathway by Thiobacillus thi- Coking wastewater was obtained from a coking facility in oparus (Kim and Katayama, 2000; Watts and Moreau, 2016)are Tangshan City, Hebei Province, China, and was treated using a well studied. However, the knowledge on key microbial taxa and bench-scale bioreactor consisting of anaerobic pretreatment and associated functional genes involved in the biotransformation of aerobic treatment (Joshi et al., 2016) for 488 days. The anaerobic nitrogen and sulfur-containing pollutants in coking wastewater pretreatment is described in the supplementary information treatment system is still very limited. In addition, how environ- (Experimental section 1). The aerobic bioreactor was operated with mental variables affect the biotransformation of these pollutants a constant hydraulic retention time (HRT) of 72 h, dissolved oxygen À1 and influence the microbial community functional structure are (DO) of 2e4mgL , and temperature of 20e25 C. The influent not clearly understood. As an important environmental factor, pH wastewater characteristics are given in supplementary information has great impact on the biotransformation (Shen et al., 2015). (Table S1). After 300 days, the pH (7.2 ± 0.3) of the aerobic biore- Considering high concentration of ammonia in coking wastewater actor