Coking Wastewater Treatment System Research Articles

Metagenomic Insight Reveals the Microbial Structure and Function of the Full-Scale Coking Wastewater Treatment System: Gene-Based Nitrogen Removal

Microbial communities play crucial roles in pollutant removal and system stability in biological systems for coking wastewater (CWW) treatment, but a comprehensive understanding of their structure and functions is still lacking. A five month survey of four sequential bioreactors, anoxic 1/oxic 1/anoxic 2/oxic 2 (A1/O1/A2/O2), was carried out in a full-scale CWW treatment system in China to elucidate operational performance and microbial ecology. The results showed that A1/O1/A2/O2 had excellent and stable performance for nitrogen removal. Both total nitrogen (TN; (17.38 ± 6.89) mg·L−1) and ammonium–nitrogen (NH4+-N; (2.10 ± 1.34) mg·L−1) in the final biological effluent satisfied the Chinese national standards for CWW. Integrated analysis of 16S ribosome RNA (rRNA) sequencing and metagenomic sequencing showed that the bacterial communities and metagenomic function profiles of A1 and O1 shared similar functional structures, while those of A2 significantly varied from those of other bioreactors (p < 0.05). The results indicated that microbial activity was strongly connected with activated sludge function. Nitrosospira, Nitrosomonas, and SM1A02 were responsible for nitrification during the primary anoxic–oxic (AO) stage and Azoarcus and Thauera acted as important denitrifiers in A2. Nitrogen cycling-related enzymes and genes work in the A1/O1/A2/O2 system. Moreover, the hao genes catalyzing hydroxylamine dehydrogenase (EC 1.7.2.6) and the napA and napB genes catalyzing nitrate reductase (EC 1.9.6.1) played important roles in the nitrification and denitrification processes in the primary and secondary AO stages, respectively. The mixed liquor suspended solids (MLSS)/total solids (TS), TN removal rate (RR), total organic carbon (TOC) (RR), and NH4+-N (RR) were the most important environmental factors for regulating the structure of core bacterial genera and nitrogen-cycling genes. Proteobacteria were the potential main participants in nitrogen metabolism in the A1/O1/A2/O2 system for CWW treatment. This study provides an original and comprehensive understanding of the microbial community and functions at the gene level, which is crucial for the efficient and stable operation of the full-scale biological process for CWW treatment.

Investigation of the nitrogen removal performance and microbial community structure in a full-scale A/O1/H/O2 coking wastewater treatment system.

Biological treatment processes are an effective method for removing the nitrogen-containing contaminants that exist in coking wastewater. However, little is known about microbial composition and keystone taxa involved in biological nitrogen removal processes. In order to improve the removal efficiency of nitrogen-containing contaminants in anaerobic-aerobic-hydrolytic-aerobic (A/O1/H/O2) system, the microbial composition and interactions of keystone taxa should be clarified. The present work clarifies the removal performance of nitrogen-containing contaminants in the A/O1/H/O2 system, identifies the microbial community involved in various bioreactors, and reveals the keystone taxa within the microbial communities. Combined the processes of ammoniation, denitrification, and nitrification, total nitrogen decreased from 248 to 31 mg L-1 and achieved a removal efficiency of 87.5% in the full-scale A/O1/H/O2 system. High-throughput MiSeq sequencing revealed that Proteobacteria was the most abundant phylum in the A/O1/H/O2 system with relative abundances of 24%-50%. Thiobacillus dominated in bioreactors A and O1 with relative abundances of 2.90% and 4.44%, respectively, while Nitrospira was identified as the most dominant genus in bioreactors H and O2, accounting for 13.33% and 18.38%, respectively. The microbial community composition and co-occurrence network analysis showed that the keystone taxa belonged to Thiobacillus, Nitrospira, Bdellovibrio, Planctomyces, Desulfotomaculum, and Sphingobium, which are related to nitrogen degradation.

Microbial community composition and function prediction involved in the hydrolytic bioreactor of coking wastewater treatment process.

The hydrolytic acidification process has a strong ability to conduct denitrogenation and increase the biological oxygen demand/chemical oxygen demand ratio in O/H/O coking wastewater treatment system. More than 80% of the total nitrogen (TN) was removed in the hydrolytic bioreactor, and the hydrolytic acidification process contributed to the provision of carbon sources for the subsequent nitrification process. The structure and diversity of microbial communities were elaborated using high-throughput MiSeq of the 16S rRNA genes. The results revealed that the operational taxonomic units (OTUs) belonged to phyla Bacteroidetes, Betaproteobacteria, and Alphaproteobacteria were the dominant taxa involved in the denitrogenation and degradation of refractory contaminants in the hydrolytic bioreactor, with relative abundances of 22.94 ± 3.72, 29.77 ± 2.47, and 18.23 ± 0.26%, respectively. The results of a redundancy analysis showed that the OTUs belonged to the genera Thiobacillus, Rhodoplanes, and Hylemonella in the hydrolytic bioreactor strongly positively correlated with the chemical oxygen demand, TN, and the removal of phenolics, respectively. The results of a microbial co-occurrence network analysis showed that the OTUs belonged to the phylum Bacteroidetes and the genus Rhodoplanes had a significant impact on the efficiency of removal of contaminants that contained nitrogen in the hydrolytic bioreactor. The potential function profiling results indicate the complementarity of nitrogen metabolism, methane metabolism, and sulfur metabolism sub-pathways that were considered to play a significant role in the process of denitrification. These results provide new insights into the further optimization of the performance of the hydrolytic bioreactor in coking wastewater treatment.

Kinetics and molecular mechanism of enhanced fluoranthene biodegradation by co-substrate phenol in co-culture of Stenotrophomonas sp. N5 and Advenella sp. B9

Polycyclic aromatic hydrocarbons (PAHs) and phenol are persistent pollutants that coexist in coking wastewater (CWW). Fluoranthene (Flu) is the predominant PAH species in the CWW treatment system. Our work emphasized on distinguishing the effects of phenol on Flu biodegradation by co-culture of Stenotrophomonas sp. N5 and Advenella sp. B9 and illustrated the molecular mechanisms. Results showed Flu biodegradation by co-culture was enhanced by phenol. According to the first-order degradation kinetic analysis of Flu, phenol significantly increased the biodegradation rate constant and shortened the half-life of Flu. Transcriptome analysis pointed out the up-regulation of DNA repair activity and 3717 significantly differentially expressed genes (DEGs), were triggered by 800 mg/L phenol. GO enrichment analysis suggested these DEGs are mainly concentrated in biochemical processes such as metal ion binding and alpha-amino acid biosynthesis, which are closely associated with Flu biodegradation, indicating that phenol promotes DNA repair activity and reduces Flu genotoxicity. qRT-PCR was performed to detect the gene expression of aromatic ring-opening dioxygenase. Combined with transcriptome analysis, the qRT-PCR results suggested phenol did not induce the expression of related PAHs-degrading enzymes. RNA extraction and microbial growth curves of COC and COC + Ph provided further evidence that phenol serves as co-substrate which increases biomass and the concentration of degrading enzymes, therefore promoting the Flu degradation.

Two-stage anoxic-oxic (A/O) system for the treatment of coking wastewater: Full-scale performance and microbial community analysis

• A full-scale AOAO coking wastewater treatment system was investigated. • Various pollutants were removed efficiently after the AOAO process. • The biodegradation dynamics of refractory organics was explored by GC × GC-TOF MS. • Composition and function of microbial community greatly altered in AOAO process. Coking wastewater (CWW) is one of the most challenging industrial wastewaters to treat, due to its complex chemical composition, high organic load, and potential toxicity to human and environmental health. A full-scale coking wastewater treatment plant with a two-stage anoxic-oxic-anoxic-oxic (A1/O1/A2/O2) process was investigated systematically. The experimental results showed that the AOAO process exhibited an excellent removal capacity of COD, ammonia, nitrate, and total nitrogen. The GC × GC-TOF MS analysis investigated that the majority of refractory organic compounds, such as phenols, quinolines, polycyclic aromatic hydrocarbons, hydrocarbons, etc., were either fully decomposed or exhibited significant decreases in concentration during the full-scale AOAO process, which offered insights to the biodegradation dynamics of CWW organic components. Microbial community analysis showed that bacterial communities were remarkably altered in the four bioreactors of the AOAO process: Proteobacteria dominated during the whole AOAO process, while Nitrospirae and Bacteroidetes enriched in the primary and secondary AO process, respectively. Moreover, metagenomic sequencing found that the relative abundances of amino acid metabolism and carbohydrate metabolism in the primary AO process were both higher than that in the secondary AO process. It indicated that as the AOAO process progressed, the changes in operational characteristics could remarkably affect the variations of functional microorganisms responsible for organics and nitrogen removal and metabolic functions of microbial community. Through this study, a comprehensive assessment of the AOAO biological processes of coking wastewater treatment was achieved, which provided valuable insights to the operation and evaluation of relevant real treatment plants.

Diversity and functional prediction of microbial communities involved in the first aerobic bioreactor of coking wastewater treatment system.

The pre-aerobic process of coking wastewater treatment has strong capacity of decarbonization and detoxification, which contribute to the subsequent dinitrogen of non-carbon source/heterotrophic denitrification. The COD removal rate can reach > 90% in the first aerobic bioreactor of the novel O/H/O coking wastewater treatment system during long-term operation. The physico-chemical characteristics of influent and effluent coking wastewater in the first aerobic bioreactor were analyzed to examine how they correlated with bacterial communities. The diversity of the activated sludge microbial community was investigated using a culture-independent molecular approach. The microbial community functional profiling and detailed pathways were predicted from the 16S rRNA gene-sequencing data by the PICRUSt software and the KEGG database. High-throughput MiSeq sequencing results revealed a distinct microbial composition in the activated sludge of the first aerobic bioreactor of the O/H/O system. Proteobacteria, Bacteroidetes, and Chlorobi were the decarbonization and detoxification dominant phyla with the relative abundance of 84.07 ± 5.45, 10.89 ± 6.31, and 2.96 ± 1.12%, respectively. Thiobacillus, Rhodoplanes, Lysobacter, and Leucobacter were the potential major genera involved in the crucial functional pathways related to the degradation of phenols, cyanide, benzoate, and naphthalene. These results indicated that the comprehensive understanding of the structure and function diversity of the microbial community in the bioreactor will be conducive to the optimal coking wastewater treatment.

Investigation of the fate of heavy metals based on process regulation-chemical reaction-phase distribution in an A-O1-H-O2 biological coking wastewater treatment system

Regulation mechanism of typical substances including OH−, CN−, SCN−, S2−, NH3 on the distribution of heavy metals was investigated in coking wastewater treatment plant with our self-designed Anaerobic-Oxic-Hydrolytic-Oxic (A-O1-H-O2) system through engineering data exposure and computational density functional theory (DFT) verification. The results showed that coking sludge had superior enrichment ability for heavy metals, especially for the sludge from the A and H tanks. The enrichment ratio of the 8 heavy metals including Cd, Pb, Ni, Zn, Cu, Hg, Cr and As in coking waste sludge was found to be 6232 (comparing to these in the influent wastewater of A-O1-H-O2 system). The distribution of 8 heavy metals was closely related to their chemical (precipitation and/or complexation) and biochemical reaction potential with OH−, CN−, SCN−, S2−, NH3 in the A-O1-H-O2 system. The regulation mechanism of these precipitation and/or complexation agents on heavy metals was confirmed by DFT calculation. The stable energy of complexes formed between typical compounds and common heavy metal ions follow the order: OH: Cu2+>Pb2+>Zn2+>Cd2+>Hg2+>Ni2+; S2−: Pb2+>Cu2+>Zn2+>Cd2+>Hg2+>Ni2+; CN−: Zn2+>Cu2+>Cd2+>Hg2+>Pb2+>Ni2+; SCN−: Zn2+>Cd2+>Pb2+>Hg2+>Cu2+>Ni2+; NH3: Cu2+>Zn2+>Cd2+>Pb2+>Hg2+>Ni2+, providing reference for the judgement of which metal ions were preferentially combined with the typical compounds in coking wastewater. The results of this paper indicated that the enrichment of heavy metal ions in coking wastewater can be achieved by process design combined with the control of operating conditions (dissolved oxygen, hydraulic retention time, sludge retention time and pH), basing on the nature of heavy metal ions. Finally, the separation and differential management of heavy metals can be achieved.

Solubilization of polycyclic aromatic hydrocarbons (PAHs) with phenol in coking wastewater treatment system: Interaction and engineering significance

Polycyclic aromatic hydrocarbons (PAHs) are accumulated in the sludge collected from the coking wastewater treatment. Phenol with its efficient degradation observed in biological treatment promotes the solubility of PAHs in aqueous phase. The interaction mechanism of phenol and PAHs in aqueous and sludge phases was systematically studied in two full-scale engineering projects composed of anaerobic-oxic-oxic (A-O1-O2) and anaerobic-oxic-hydrolytic-oxic (A-O1-H-O2) sequences. The results showed that reasonable use of phenol facilitates solubilization of PAHs alleviating their emission problems. The ΔPAHs/Δphenol mass ratio in the sludge phase of A-O1-H-O2 system (146.3) exceeded that in A-O1-O2 one (63.80), exhibiting a good solubilization effect on PAHs with their more efficient degradation in the former. The full-scale observations were verified in laboratory solubilization experiments using phenanthrene (Phen), pyrene (Pyr) and benzo[a]pyrene (Bap) as the models of 3-, 4- and 5-ring PAHs, respectively. The binding energies of [phenol−PAHs] complexes were calculated using computational density functional theory showing consistency with the experimentally observed phenol-facilitated solubilization efficiencies in the row of Phen>Pyr>Bap. The results showed the fate and distribution of PAHs in coking wastewater treatment affected by the presence of phenol serving as a cost effective reagent for enhanced solubilization of PAHs from the coking wastewater sludge.

Levels, Sources, and Health Risk Assessments of Heavy Metals in Indoor Dust in a College in the Pearl River Delta

Thirty indoor dust samples were collected from staff and study areas in a college in Foshan, and the As, Hg, Cd, Cu, Zn, Ni, Pb, and Cr contents were measured. The Spearman correlation coefficient, principal component analysis, and US EPA health risk assessment model were used to determine the sources and degree of pollution and the health risks. The results showed that the levels of the eight heavy metals were higher than the background values in Guangdong Province and the reported values in other Chinese cities, excluding Hg. The levels of the eight heavy metals were higher in the staff area than in the study area, but the difference was not significant. The eight heavy metals were derived from similar sources; Hg was mainly derived from outdoor anthropogenic sources, while the others were mainly derived from indoor anthropogenic sources. The daily non-carcinogenic exposure dose was in the following order:ingestion > dermal exposure > inhalation. Ingestion was the major pathway of heavy metal exposure from indoor dust. Except for Cr, the non-carcinogenic hazard indexes of ingestion and dermal exposure were taken from partial sample points > 1. All of the health risks were lower than the average risk thresholds of the heavy metals, and would not cause health risks to humans. Printers, copiers, instruments, and equipment were important sources of indoor pollution and risk sources of heavy metals. Thus, protective measures should be taken to reduce the risk of exposure.

Characteristics of microbial community functional structure of a biological coking wastewater treatment system

Nitrogenous heterocyclic compounds are key pollutants in coking wastewater; however, the functional potential of microbial communities for biodegradation of such contaminants during biological treatment is still elusive. Herein, a high throughput functional gene array (GeoChip 5.0) in combination with Illumina HiSeq2500 sequencing was used to compare and characterize the microbial community functional structure in a long run (500days) bench scale bioreactor treating coking wastewater, with a control system treating synthetic wastewater. Despite the inhibitory toxic pollutants, GeoChip 5.0 detected almost all key functional gene (average 61,940 genes) categories in the coking wastewater sludge. With higher abundance, aromatic ring cleavage dioxygenase genes including multi ring1,2diox; one ring2,3diox; catechol represented significant functional potential for degradation of aromatic pollutants which was further confirmed by Illumina HiSeq2500 analysis results. Response ratio analysis revealed that three nitrogenous compound degrading genes- nbzA (nitro-aromatics), tdnB (aniline), and scnABC (thiocyanate) were unique for coking wastewater treatment, which might be strong cause to increase ammonia level during the aerobic process. Additionally, HiSeq2500 elucidated carbozole and isoquinoline degradation genes in the system. These findings expanded our understanding on functional potential of microbial communities to remove organic nitrogenous pollutants; hence it will be useful in optimization strategies for biological treatment of coking wastewater.

Biotransformation of nitrogen- and sulfur-containing pollutants during coking wastewater treatment: Correspondence of performance to microbial community functional structure

Although coking wastewater is generally considered to contain high concentration of nitrogen- and sulfur-containing pollutants, the biotransformation processes of these compounds have not been well understood. Herein, a high throughput functional gene array (GeoChip 5.0) in combination with Illumina MiSeq sequencing of the 16S rRNA gene were used to identify microbial functional traits and their role in biotransformation of nitrogen- and sulfur-containing compounds in a bench-scale aerobic coking 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 community functional structure was significantly associated with pH (Mantels test, P < 0.05). The release of ammonia nitrogen and sulfate was correlated with both the taxonomic and functional microbial community structure (P < 0.05). Considering the abundance and correlation with the release of ammonia nitrogen and sulfate, aromatic dioxygenases (e.g. xylXY, nagG), nitrilases (e.g. nhh, nitrilase), dibenzothiophene oxidase (DbtAc), and thiocyanate hydrolase (scnABC) were important functional genes for 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 (7.0–7.5) for stability of the biological system treating coking wastewater.

The Resilience of Microbial Community Involved in Coking Wastewater Treatment System

Biological treatment processes are the most important step for removing various nutrient matters due to their high removal efficiency and low operational cost. The activated sludge technology was used extensively in coking wastewater biological treatment processes where a complex prokaryotic microbial consortium played an important role in the processes of oxygen-depleting organics, toxics and nutrients removal and preventing discharge of pathogens. Thus, a thorough knowledge of the ecology of the coking wastewater activated sludge communities is required to improve system operation and stability. Therefore, there is necessary to reveal the resilience of microbial community involved in coking wastewater treatment system.

Contrasting microbial community composition and function perspective in sections of a full-scale coking wastewater treatment system.

To characterize the microbial community of the coking wastewater (CWW) treatment system and to study the effects of CWW characteristics and operational parameters on microbial communities, active sludge samples were collected from a full-scale CWW treatment plant using three-phase fluidized bed biological reactors. High-throughput MiSeq sequencing was used to examine the 16S rRNA genes of microbiology, revealing a distinct microbial composition among the active sludge samples of three sequential bioreactors. Pseudomonas, Comamonas, and Thiobacillus-related sequences dominated in the anaerobic bioreactor A, aerobic bioreactor O1, and aerobic bioreactor O2 active sludge with relative abundance of 72.59, 56.75, and 27.82 %, respectively. The physico-chemical characteristics of CWW were analyzed by standard methods and operational parameters were recorded to examine their effects on the microbial communities. The redundancy analysis (RDA) results showed that the bacterial communities of bioreactors A, O1, and O2 correlated strongly with cyanides, phenols, and ammonia, respectively. These results expand the knowledge about the biodiversity and population dynamics of microorganisms and discerned the relationships between bacterial communities and environmental variables in the biological treatment processes in the full-scale CWW treatment system.

Pyrene degradation by Pseudomonas sp. and Burkholderia sp. enriched from coking wastewater sludge

A pyrene-degrading consortium was enriched from sludge of coking wastewater treatment plant which included a combination of aerobic and anaerobic reactors. Biodegradation of pyrene by the consortium follows first-order kinetics. Addition of a co-substrate (glucose or anthraquinone) facilitated pyrene degrading. The highest degradation rate was achieved at 35°C and pH 7.0, as glucose was added. In this case, pyrene (100 mg L−1) was degraded by 93.1 % within 36 h. An intermediate, 1-naphthol was detected via GC-MS analysis, indicating that pyrene degradation by the consortium proceeded with a pathway different from that associated with Mycobacterium sp. By comparisons of 16S rRNA gene sequences, two strains in this consortium were identified as Pseudomonas sp. and Burkholderia sp. The enriched pyrene-degrading consortium from coking wastewater treatment system shows highest pyrene-degrading activity compared with the reported pyrene degraders.

Study of the Treatment of Coking Wastewater by Biological Nitrogen Removal with Physical-Chemical Process

Coking wastewater component complex is difficult to treat and yet unable to achieve the emission target by biological treatment, thus needs further processing. Wastewater treatment plant of coking plant in Bao Gang applied A/O process in biological treatment, used special treatment agent -M180 by coagulation and sedimentation process. Through treatment, the parameters reached the first grade of GB13456-92. It is of great reference significance for process debug and operation of the coking wastewater treatment system.

Cloning of Environmental Genomic Fragments as Physical Markers for Monitoring Microbial Populations in Coking Wastewater Treatment System

The association between community functional shift and dynamics of genomic DNA composition can be used to identify functionally relevant populations as indicator organisms for systems monitoring. In this work, fingerprinting-based community DNA hybridization was used to monitor community structural dynamics and identify genomic fragments whose abundance shifts were concomitant to changes in COD removal capacity in a reactor. A laboratory-scale anaerobic-anoxic-oxic fixed biofilm system treating coking wastewater was operated with (LR mode) or without effluent recirculation (LNR mode). The contribution to total chemical oxygen demand (COD) removal by the anoxic reactor increased from 4% in LNR mode to 26% in LR mode. Long primer RAPD (randomly amplified polymorphic DNA) community fingerprints of the anoxic reactor also changed most significantly from the one similar to the anaerobic reactor to one similar to the oxic reactor. DNA hybridization revealed one signature band of 2.1 kb shared by the anoxic and oxic reactors in LR, but not LNR mode. Clone library profiling of this band resulted in one predominant 2.1-kb genomic fragment (B3) with no homologous sequences in GenBank. Real-time polymerase chain reaction indicated that copy numbers of B3 in the anoxic reactor under LR mode were 69 times higher than that under LNR mode, concomitant to a significant increase in COD removal capacity in this reactor. The different patterns of distribution of B3 in the laboratory system and a comparable malfunctioning industrial system demonstrated the potential of this genomic fragment as physical markers in systems monitoring. In addition, this genomic fragment may allow sequence-guided isolation of the host microbe.