Bio-treated Coking Wastewater Research Articles

Enhanced removal of nitrate and refractory organic pollutants from bio-treated coking wastewater using corncobs as carbon sources and biofilm carriers

The quality of the bio-treated coking wastewater (BTCW) is difficult to meet increasingly stringent coking wastewater discharge standards and future wastewater recycling needs. In this study, the pre-treatment process of BTCW was installed including the two up-flow fixed-bed bioreactors (UFBRs) which were separately filled with alkali-pretreated or no alkali-pretreated corncobs used as solid carbon sources as well as biofilm carriers. Results showed that this pre-treatment process could significantly improve the biodegradability of BTCW and increase the C/N ratio. Thus, over 90% of residual nitrate in BTCW were removed stably. Furthermore, GC-MS analysis confirmed that the typical refractory organic matters decreased significantly after UFBRs pre-treatment. High-throughput sequencing analysis using 16S rRNA demonstrated that dominant denitrifiers, fermentative bacteria and refractory-organic-pollutants-degrading bacteria co-existed inside the UFBRs system. Compared with no alkali-pretreated corncobs, alkali-pretreated corncobs provided more porous structure and much stable release of carbon to guarantee the growth and the quantity of the functional bacteria such as denitrifiers. This study indicated that the UFBRs filled with alkali-pretreated corncobs could be utilized as an effective alternative for the enhanced treatment of the BTCW.

Chemical oxygen demand (COD) removal from bio-treated coking wastewater by hydroxyl radicals produced from a reduced clay mineral

Removal of chemical oxygen demand (COD) from wastewater has been of considerable interest for several decades, but detailed mechanisms are poorly known. Here we present an environmental friendly method for removing COD from coking wastewater by using chemically reduced nontronite (rNAu-2). Hydroxyl radicals (·OH) produced from oxidation of structural Fe(II) in rNAu-2 in phosphate buffer at pH 6.5, oxidized various compounds in wastewater and thus significantly decreased COD (from 199.10 ± 0.90 to 80.4 ± 1.97 mg/L) within 120 h. The amount of COD removal was positively correlated with the amount of ·OH production, with removal efficiency depending on pH and buffer type. Mass spectrometric analysis of dissolved organic matter (DOM) suggested an oxidative pathway for COD removal. Excitation-emission matrix (EEM) fluorescence spectroscopy showed that aromatic protein-like compounds accounted for a large fraction of DOM in initial wastewater, but after rNAu-2 treatment, their proportion decreased. A sequential treatment of wastewater by rNAu-2 and a common wastewater bacterium Alcaligenes faecalis demonstrated that different orders of chemical and biological treatments affected COD removal efficiency, likely because chemical and microbial treatments targeted different compounds in coking wastewater.

Residual chemical oxygen demand (COD) fractionation in bio-treated coking wastewater integrating solution property characterization

The refractory nature of residual COD in bio-treated coking wastewater (BTCW) creates barriers for its further treatment and reclamation. It is necessary to fractionate the residual COD in BTCW associated with characterization of solution properties. In this paper, a stepwise process composed of membrane filtration, coagulation, adsorption and ozonation was proposed to fractionate residual COD in the BTCW, in which the COD was stepwise reduced to near zero. In addition, the correlation between COD and water quality indexes as well as solution properties were discussed together with a safety assessment of the water quality. Results showed that the residual COD fractionation percentage contributed by suspended solids, colloids, dissolved organics and reductive inorganic substances in the BTCW was 43.7%, 22.1%, 26.2% and 4.9%, respectively. By stepwise fractionating of these substances, the residual COD was reduced from 168.8 to 5.2 mg L−1, and the UV254 value decreased from 1.90 to 0.15 cm−1. In addition, the particle size of the dominant substances contributing to the residual COD was smaller than 450 nm. Among these substances, the hydrophobic fraction accounted for 78.66% (in the term of TOC). Three-dimensional excitation-emission matrix (3D-EEM) analysis showed that hydrophobic neutral substances (HON) were the main fluorescence constituent in the BTCW, which was highly removable by adsorption. The residual COD after adsorption was mainly composed of reductive inorganic substances. Apart from pursuit of high COD removal rates, more emphasis should be given to the removal of toxic COD. Correlations were observed between the residual COD and water quality indicators as well as solution properties, providing a guideline for optimized removal of residual COD in the BTCW. In summary, these results gave a referential information about the nature of residual COD in the BTCW for the selection of advanced treatment technologies and the management of water quality safety.

Material inter-recycling for advanced nitrogen and residual COD removal from bio-treated coking wastewater through autotrophic denitrification

For wastewaters containing high strength sulfide and nitrogen (e.g. coking wastewater), sulfide might be precipitated and recovered using ferrous salt. This study systematically investigated the feasibility of recovered and precipitated FeS (comparing to commercial FeS minerals) to support autotrophic denitrification for advance nitrogen removal from bio-treated coking wastewater in fluidized bed reactors. The reactor with precipitated FeS could achieve simultaneous removal of NO3−-N and inert COD with high efficiencies of around 96.3% and 30.5%, at NO3−-N and COD loading rates of 4.18 mg·L−1·h−1 and 8.06 mg·L−1·h−1, respectively. Whereas, the performance of commercial FeS reduced gradually and irreversibly after two days, which became completely ineffective after 40 days. Thiobacillus and Rhodanobacter dominated the biomass, which played a key role in the FeS-based denitrification process. This material inter-recycling concept benefits an advance and more sustainable treatment of wastewaters with high strength sulfide and nitrogen.

Effective mineralization of quinoline and bio-treated coking wastewater by catalytic ozonation using CuFe2O4/Sepiolite catalyst: Efficiency and mechanism

In this study, CuFe2O4 nanocomposite loaded on natural sepiolite (CuFe2O4/SEP) was prepared by the citrate sol-gel method. CuFe2O4/SEP was characterized by X-ray diffraction, Brunauer-Emmett-Teller adsorption analysis, scanning electron microscopy, and energy dispersive spectroscopy. The CuFe2O4/SEP composite was stable and showed an excellent catalytic activity for ozonation. The efficiency of quinoline mineralization in the catalytic ozonation with CuFe2O4/SEP was 90.3%, and this value was 5.4 times higher than that of the uncatalyzed ozonation (16.8%). The quinoline mineralization followed a pseudo first-order kinetics with all the catalysts. The rate constant for the mineralization of quinoline by ozonation in the presence of CuFe2O4/SEP was 0.0885 min−1, which was 16.7 times higher than that in ozone alone (0.0053 min−1). Radical scavenging tests revealed that hydroxyl radical (OH) and superoxide radical (O2−) were the reactive oxygen species (ROS) in the quinoline degradation. In the presence of CuFe2O4/SEP, ozone and hydrogen peroxide were rapidly converted into the ROS. Although neutral and alkaline pH were more beneficial for the quinoline mineralization, CuFe2O4/SEP exhibited significant catalytic activity even under acidic conditions. Meanwhile, five-cycle successive tests suggested that CuFe2O4/SEP was recyclable and hence, stable. Furthermore, the feasibility of the catalytic ozonation for the treatment of biologically treated coking wastewater was evaluated. The catalytic ozonation resulted in 57.81% total organic carbon removal efficiency at 60 min, which was 2.9 times higher than that in the uncatalyzed ozonation (19.99%).

Characteristics and mechanisms of catalytic ozonation with Fe-shaving-based catalyst in industrial wastewater advanced treatment

Iron shavings were modified and used as the catalyst (named as Fe-shaving-based catalyst) for the ozonation of bio-treated coking wastewater. The difference of organic pollutants oxidation between catalytic and sole ozonation processes was characterized by MW (Molecular Weight) distribution and 3DEEM (Three-dimensional Excitation and Emission Matrix Fluorescence) analysis. Removals of the pollutants with MW of 5–10 kDa and 10–20 kDa in catalytic ozonation process were 81.5% and 85.2%, which were far better than that in sole ozonation process (31.1% and 41.8%). Organics with MW of 0.3–2 kDa and 2–5 kDa would accumulate in both two processes, while the accumulation amount in catalytic ozonation process was half of it in sole ozonation process. The removal of fluorescent substances in catalytic ozonation process experienced a procedure of lower firstly (<15 min) and then higher (>15 min) than that in sole ozonation process. The slight residual fluorescent substances were completely removed in catalytic ozonation process, while remained unchanged in sole ozonation process with the reaction time increasing to 180 min. The catalytic effect of Fe-shaving-based catalyst was better than commonly used powder catalysts and the TOC (Total Organic Carbon) removal attained to 78%. Hydroxyl radicals (·OH) were confirmed to be the effective oxidant in catalytic ozonation process through inhibition experiments. The cumulative ·OH formations with 200 g/L Fe-shaving-based catalyst during 180 min were 362 μmol, which explained the better catalytic effect of it. The surface hydroxyl groups were determined to be the most probable active sites for ·OH generation through phosphate inhibition experiments. Besides the excellent catalytic effect, using Fe-shaving-based catalyst provided a feasible resource utilization method of industrial waste Fe-shavings. Thereby, it is a promising catalyst for practical industrial wastewater advanced treatment with catalytic ozonation process.

In-Situ Synthesis and High-Efficiency Photocatalytic Performance of Cu(I)/Cu(II) Inorganic Coordination Polymer Quantum Sheets.

Two-dimensional (2D) materials ultrathin quantum sheets have the advantage of elevating the catalysis performance and prominent edge effects, but most of them belong to element single valence materials. In this paper, the ultrathin Cu(I)/Cu(II) inorganic coordination polymer quantum sheet (ICPQS) {[CuII(H2O)4][CuI4(CN)6]} n is synthesized by controlling the appropriate molar ratio of raw material, reaction time, and temperature. Transmission electron microscopy (TEM) and atomic force microscope (AFM) analysis show that this ICPQS has a thickness of ∼0.2 nm. Due to the fact that about 58.16% of the Cu(I)/Cu(II) is occupied in molecular structure and most of the metal active sites are fully utilized, this ICPQS can accelerate the photocatalytic degradation of methylene blue (MB) (K = 2.5 mg·L-1·min-1 at pH 3) and organic compounds in coking wastewater and biotreated coking wastewater. Basing on mixed valences, the ICPQS can use visible light to promote energy transfer and increase quantum efficiency, paving the way for developing the next-generation monolayer 2D mixed valence photocatalysts.

Advanced treatment of biotreated coking wastewater with peroxymonosulfate oxidation catalyzed by granular activated carbon

AbstractBACKGROUNDAfter biological treatment, coking wastewater contains high concentrations of toxic organic contaminants and thus requires further treatment.RESULTSAdvanced treatment of biotreated coking wastewater (BTCW) with peroxymonosulfate (PMS) oxidation catalyzed by granular activated carbon (GAC) at ambient temperature (25 °C) was comprehensively investigated. The GAC/PMS system exhibited higher efficiency for total organic carbon (TOC) removal from BTCW than did the PMS‐only and GAC‐only systems. Up to 75.7% of TOC was removed over a 5 h period with 2 g L‐1 of KHSO5 and 10 g L‐1 of GAC at an initial pH of approximately 5. The TOC removal efficiency increased with PMS concentration and GAC dosage; however, the superfluous PMS was not conducive to organic degradation. The PMS decomposition followed a first‐order kinetics behavior. The GAC/PMS system's capacity for TOC removal gradually weakened with increase in the number of times the GAC was reused. Almost half of the removal rate was retained after four uses of GAC. The excitation–emission matrix fluorescence demonstrated that humic‐acid‐like substances are effectively adsorbed and preferentially decomposed in wastewater.CONCLUSIONThe study suggests that it is feasible for advanced treatment of BTCW with PMS oxidation catalyzed by GAC, achieving high efficiency for TOC removal. © 2017 Society of Chemical Industry

Correction to: The mineralization of oxalic acid and bio-treated coking wastewater by catalytic ozonation using nickel oxide.

In Table 1, "SO2-4" and "NO-3" should be corrected to "[Formula: see text]" and "[Formula: see text]", respectively. The original article was corrected.

The mineralization of oxalic acid and bio-treated coking wastewater by catalytic ozonation using nickel oxide.

Coking wastewater after biological treatment still possesses potential environmental risk and should be mineralized further. This work focused on the mineralization of bio-treated coking wastewater using catalytic ozonation by NiO. First, oxalic acid, the typical by-product of advanced oxidation process (AOPs), was used to test the catalytic performance of NiOs, prepared by modified hydrothermal methods upon addition of different surfactants. This demonstrated that NiO upon addition of hexadecyltrimethylammonium (CTAB) had the best catalytic activity, due to its high concentration surface hydroxyl density and strong stability. Moreover, the best NiO was applied for the catalytic ozonation of bio-treated coking wastewater. Under our experimental conditions, the total organic carbon (TOC) removal reached 100% after 420min. In addition, the spectroscopic analysis suggested that compounds with conjugated structures could be significantly removed by both ozonation and catalytic ozonation. Some of these substances were transformed into by-products with aliphatic C-C and O=C-O groups such as organic acids that can inhibit further mineralization.

Factors controlling adsorption of recalcitrant organic contaminant from bio‐treated coking wastewater using lignite activated coke and coal tar‐derived activated carbon

AbstractBACKGROUNDLow‐cost coal‐based carbonaceous material has attracted special attention for removal of organics from industrial wastewaters. In this study, coal tar‐derived activated carbon (AC1) and lignite activated coke (AC2) were employed to identify the fundamental factors that facilitate the selection of suitable adsorbents for removing recalcitrant organic contaminant (ROC) from bio‐treated coking wastewater (BTCW).RESULTSResults show that AC2 exhibited superior ROC adsorption efficiency (57.9%), which was apparently higher than that of AC1 (45.2%), in spite of its lower specific surface area (238.05 m2 g−1) and pore volume (0.21 cm3 g−1). FTIR and XPS characterization indicated that AC2 possessed a distinctive configuration of functional groups, of which the basic oxygenic groups (60%) provided more hydrophobic adsorption sites for ROC. 3D‐EEM spectra suggested more aromatics and fluorescent materials were removed by AC2 compared with AC1. GC‐MS further confirmed that AC2 had stronger affinity with the ROC in BTCW, especially for PAHs and heterocyclic compounds.CONCLUSIONSurface chemistry is vital to the adsorption of ROC from coking wastewater, of which basic oxygenic functional groups have specific interactions with PAHs and heterocyclic compounds. The mechanism that best explains ROC adsorption is π–π dispersion between carbon materials and the pollutants, as well as the hydrogen‐bonding interactions. This study provides an encouraging and practical guide to ROC adsorption from BTCW in future operations. © 2017 Society of Chemical Industry

Dissolved organic matter (DOM) removal from bio-treated coking wastewater using a new polymeric adsorbent modified with dimethylamino groups

In the current study a new recyclable aminated hyper-cross-linked polymeric adsorbent (A-HPA) was prepared for effective removal of DOM from BTCW. Possibly benefited from its unique structure of polystyrene matrix, sufficient aminated groups and high specific surface area, A-HPA could remove DOM from BTCW through the synergetic effect of π-π interactions, acid-base interactions and micropore filling, and exhibited the highest removal efficiency than the other adsorbents. Moreover, the exhausted A-HPA was amenable to effective regeneration by using acid and alkaline solution, allowing for repeated use with a constant removal efficiency. Field application of continuous 3-year fixed-bed runs demonstrated that A-HPA is capable of effectively removing DOM from BTCW with no significant capacity loss, and the treated effluent can be partially used as recycled water in production. All the above results demonstrated that A-HPA adsoption could serve as a good choice for the advanced treatment of bio-treated sewage effluent.

Bio-refractory organics removal and floc characteristics of poly-silicic-cation coagulants in tertiary-treatment of coking wastewater

Poly-silicic-cation coagulants are increasingly being used to remove the bio-refractory organic compounds from industrial wastewaters, yet the research on the interactions between the coagulants and organics remains limited. In this study, three composite coagulant poly-aluminum-silicate-chloride (PASiC), poly-ferric-silicate-chloride (PFSiC) and poly-aluminum-ferric-silicate-chloride (PAFSiC) were prepared and examined as tertiary-treatment coagulants for coking wastewater. Excitation-emission fluorescence (EEM) spectra and gas chromatograph/mass spectroscopy (GC/MS) were applied to characterize composition of the organics, and the floc characteristics were monitored using a laser diffraction particle size analyzer and a particle vision system. The results show that a board range of organics including microbial metabolites, fulvic acid and humic acid-like fluorophores and polymeric aromatic hydrocarbons, can be removed by PAFSiC. This is attributed to the synergetic removal of organic compounds by aluminum and iron based poly-silicic salts. Compared with PASiC and PFSiC, the resultant flocs of PAFSiC have the moderate size and porous inner structure, with more branch-like units but less agglomeration. The structure is favorable for capture, adsorption and enmeshment of the bio-refractory organic compounds from the bio-treated coking wastewater. This study indicates that the organic removal is closely related to floc characteristics and PAFSiC can be used as an effective and promising coagulant for tertiary-treatment of coking wastewater.

Removal of recalcitrant organic pollutants from bio-treated coking wastewater using coal-based carbonaceous materials

Removal of recalcitrant organic pollutants from bio-treated coking wastewater using coal-based carbonaceous materials

Zinc ferrite catalysts for ozonation of aqueous organic contaminants: phenol and bio-treated coking wastewater

Abstract The studies in ozonation catalysis present a trend in development of advanced oxidation processes (AOPs) applied to the wastewater treatment. The zinc ferrite (ZnFe 2 O 4 , ZFO) catalysts were synthesized hydrothermally (ZFO-H) and using the citrate sol–gel (ZFO-C) method with their characterization by XRD, Raman spectrum, SEM, XPS and FT-IR techniques. The objectives of this study include examining the performance of the catalysts in oxidation of phenol and pollutants in biologically treated coking wastewater (BTCW), compared to non-catalytic ozonation, and evaluating the ozonation reaction kinetics. The changes in the composition of BTCW on course of treatment were determined by ultraviolet–visible (UV) absorption and three-dimensional excitation–emission matrix spectroscopy (3DEEMs) analyses. The experimental results showed the ZFO-H catalyst accelerating the degradation of phenol for about 1.5 times as compared to non-catalytic ozonation. The catalytic activity of ZFO-H surpassed that of ZFO-C in phenol removal, attributed to the larger contact surface area and higher surface hydroxyl group density. The higher catalytic activity of ZFO-H was also confirmed by the ability of decomposing ozone and generating hydroxyl radicals ( OH). The empirical model developed in the research indicates the catalyst concentration and the ozone concentration to be the most significant factors of the reaction apparent rate; the role of pH appeared to be minor. The presence of catalysts leads also to a higher mineralization efficiency of BTCW pollutants compared to non-catalytic ozonation. The UV and 3DEEMs analysis demonstrated effective removal of the aromatic and conjugated structural compounds in BTCW by catalytic ozonation. The performance of the catalysts is determined primarily by their synthesis method defining the surface properties.

Electrochemical Oxidation Using BDD Anodes Combined with Biological Aerated Filter for Biotreated Coking Wastewater Treatment

Coking wastewater is characterized by poor biodegradability and high microorganism toxicity. Thus, it is difficult to meet Grade I of Integrated Wastewater Discharge Standard of China by biological treatment technology; specifically, COD cannot meet above standard due to containing refractory organics. A novel coupling reactor, electrochemical oxidation using BDD anodes and biological aerated filter (BAF), has been developed for carbon and nitrogen removal from biotreated coking wastewater, focusing on COD, BOD5,NH4+-N, andNO3--N removal on operation over 90 days with average effluent value of 91.3, 9.73, 0.62, and 13.34 mgL−1, respectively. Average value of BOD5/COD and BOD5/NO3--N was enhanced from 0.05 to 0.27 and from 0.45 to 1.21 by electrochemical oxidation, respectively, with average energy consumption of 67.9 kWh kg−1COD. In addition, the refractory organics also were evidently mineralized in the unit based on the data of the three-dimensional fluorescence spectra. Meanwhile, its effluent provided excellent substrate for biological denitrification in BAF. At hydraulic retention time (HRT) of 13.08 h, about 12 mgL−1 NO3--N was depleted through denitrification, and it mainly occurred at top of 0.25 m height of BAF. Therefore, it is feasible to apply the coupling reactor for biotreated coking wastewater treatment and achieve desirable effluent quality.

Effluent characteristics of advanced treatment for biotreated coking wastewater by electrochemical technology using BDD anodes.

Effluent of biotreated coking wastewater comprises hundreds of organic and inorganic pollutants and has the characteristics of high toxicity and difficult biodegradation; thus, its chemical oxygen demand cannot meet drainage standards in China. A boron-doped diamond anode was selected for advanced treatment of biotreated coking wastewater, and considering the efficiency of the removal of total organic carbon and energy consumption, optimal conditions were obtained as current density of 75 mA cm(-2), electrolysis time of 1.5 h, and an electrode gap of 1.0 cm in an orthogonal test. Effluent characteristics were investigated at different electrolysis times. The ratio of the 5-day biochemical oxygen demand (BOD5) to the chemical oxygen demand increased from an initial value of 0.05 to 0.65 at 90 min. Fluorescence spectra were used to evaluate the evolution of refractory organics. Two fluorescence peaks for raw wastewater, corresponding to an aromatic protein-like substance II and humic acid-like substance, weakened at 30 and at 90 min, only the former was detected. The specific oxygen uptake rate was used to assess effluent toxicity, and an obvious inhibition effect was found at 15 min; then, it was significantly faded at 30 and 45 min. The BOD5/NO3 (-)-N ratio increased from an initial value of 0.48 to 1.25 at 45 min and then gradually dropped to 0.69 at 90 min. According to the above effluent characteristics, it is strongly suggested that electrochemical technology using boron-doped diamond anodes is combined with biological denitrification technology for the advanced treatment of biotreated coking wastewater.

Combination of ozonation and biological aerated filter (BAF) for bio-treated coking wastewater

Laboratorial scale experiments were conducted in order to investigate the effect of ozonation as well as the combined ozonation and biological aerobic filter (BAF) on treating the bio-treated coking wastewater (BTCW). The study showed that the optimum parameters for oxidizing BTCW by ozone were the ozone dose of 0.3mgO3(applied)/mgCOD0 (about 60mg/L), 50min contact time and 7.5 pH, obtaining higher biodegradability of about 0.43 BOD5/COD ratio than the original about 0.09 for feed. The results from the combined ozonation and BAF revealed that compared to the process of the BAF alone, the combined process is more effective in abating COD, BOD5, NH4+N, color and UV254 of BTCW simultaneously, which removal rates reached about 49.7%, 58.8%, 75.8%, 91.1% and 82.3%, respectively. Therefore, the combined process is a promising technology for polishing BTCW.

Effective removal of effluent organic matter (EfOM) from bio-treated coking wastewater by a recyclable aminated hyper-cross-linked polymer

Effluent organic matter (EfOM) is a complex matrix of organic substance mainly from bio-treated sewage effluent and is considered as the main constraint to further advanced treatment. Here a recyclable aminated hyper-cross-linked polymeric adsorbent (NDA-802) featured with aminated functional groups, large specific surface area, and sufficient micropore region was synthesized for effective removal of EfOM from the bio-treated coking wastewater (BTCW), and its removal characteristics was investigated. It was found that hydrophobic fraction was the main constituent (64.8% of DOC) in EfOM of BTCW, and the hydrophobic-neutral fraction had the highest SUVA level (7.06 L mg−1 m−1), which were significantly different from that in the domestic wastewater. Column adsorption experiments showed that NDA-802 exhibited much higher removal efficiency of EfOM than other polymeric adsorbents D-301, XAD-4, and XAD-7, and the efficiency could be readily sustained according to continuous 28-cycle batch adsorption–regeneration experiments. Moreover, dissolved organic matter (DOM) fractionation and excitation-emission matrix (EEM) fluorescence spectroscopy study indicated that NDA-802 showed attractive adsorption preference as well as high removal efficiency of hydrophobic and aromatic compounds. Possibly ascribed to the presence of functional aminated groups, relatively large specific surface area and micropore region of the unique polymer, NDA-802 possesses high and sustained efficiency for the removal of EfOM, and provides a potential alternative for the advanced treatment.