Coal Chemical Wastewater Treatment Research Articles

Hydrothermal synthesis of high crystallinity ZSM-5 zeolite from coal gasification coarse slag and mother liquor circulation for efficient coal chemical wastewater purification.

A hydrothermal synthesis method was developed to produce high crystallinity ZSM-5 zeolite using coal gasification coarse slag (CGCS) as the raw material. Instead of the expensive NaOH(s.), Na2SiO3(s.) was utilized to activate, depolymerize, and recombine Si and Al elements in the CGCS. The mother liquor circulation technology was employed to recover and reuse raw materials and residual reagents (Na2SiO3(aq.) and TPABr), reducing waste emissions and enhancing resource utilization efficiency. The synthesized ZSM-5 had a specific surface area of 455.675 m2g-1, pore volume of 0.284 cm3g-1, and pore diameter of 2.496nm. The influence of various factors on the morphology and crystallinity of ZSM-5 was investigated, resulting in the production of ZSM-5 with higher specific surface area and pore volume. Adsorption experiments showed that WU-ZSM-5 exhibited a removal efficiency of 85% for ammonia nitrogen (NH4+-N(aq.)), validating its effectiveness in coal chemical wastewater purification. The mother liquor recycling technology enabled zero-emission utilization of solid waste resources and improved the utilization rate of alkali and template to 90%. These results demonstrate the potential application of the developed method in the efficient treatment of coal chemical wastewater.

Degradation of phenol by Cu-Ni bimetallic-doped sludge biochar as a fenton-like catalyst: Mechanistic study and practical application

In this study, the sewage sludge was converted into sludge biochar (SBC) and doped with Cu-Ni bimetal to synthesize a novel composite catalyst (Cu-Ni@SBC) for the activation of H2O2 for phenol degradation. Characterization results showed that the Cu-Ni bimetal was successfully doped into the SBC and led to the formation of a porous structure with abundant cavities, resulting in a larger specific surface area and higher adsorbed oxygen content. Mechanism analysis revealed a valence state conversion cycle between Cu0-Cu(II), Ni(III)-Ni(II) and Cu-Ni which made Cu-Ni@SBC have higher electron transfer performance. Response surface methodology was applied to determine the optimal preparation and reaction conditions, under which the Fenton-like system composed of Cu-Ni@SBC and H2O2 removed 100 % of phenol and mineralized 69.1 % of TOC from simulated wastewater. In addition, the experimental results showed that the Cu-Ni@SBC material had a relatively wide pH adaptation range (4–8), and the removal efficiency of phenol could reach 76.4 % after 5 cycles of experiments, and the catalytic inhibition rates of the two common coexisting anions, HCO3– and Cl-, were 17.1 % and 0 %, respectively. The results of practical application revealed that the phenol removal efficiency reached 90.44 % and the pollutant mineralization rate could reach 58.5 % within 90 min, which proved that the catalyst was suitable for the advanced degradation of organic matter in coal chemical wastewater. Therefore, Cu-Ni@SBC can be considered as a promising Fenton-like catalyst, and the process method is also of some guiding significance for the treatment of coal chemical wastewater.

Analysis and standardization of coal chemical wastewater treatment and reuse systems

To meet the practical needs of classified collection, graded treatment, and quality recycling of coal chemical wastewater, and in accordance with the standardization requirements of wastewater resource utilization, the Standardization Administration of China released the national standard GB/T 42,866-2023 ″Guidelines for Coal Chemical Wastewater Treatment and Recycling Technology” on August 6, 2023, for the first time. Based on the standard, this paper comprehensively and systematically sorts out and analyzes the characteristics, processes, water circulation systems, and standardization paths of units such as coal chemical wastewater collection and treatment, recycling, and the treatment of concentrated brine water, through extensive industry research. Furthermore, by integrating typical engineering case practices, this paper explains the feasibility of the paths, which provides technical guidance and experience for relevant cases of coal chemical wastewater treatment and recycling. It is also of great importance for promoting the standardized management and development of coal chemical wastewater treatment and recycling worldwide.

Case Study on the Design Engineering of Deodorization System in Coal Chemical Wastewater Treatment Plants in the New Era

Case Study on the Design Engineering of Deodorization System in Coal Chemical Wastewater Treatment Plants in the New Era

Membrane fouling and influencing factors of a submerged commercial ceramic flat membrane bioreactor in treatment of coal chemical wastewater

An anoxic/oxic (A/O) treatment unit was upgraded using a submerged commercial ceramic flat-membrane bioreactor. The upgraded bioreactor effectively treated coal chemical wastewater. However, the factors influencing membrane fouling remain unclear. Thus, this study explored the mechanisms of membrane fouling of a commercial ceramic flat membrane bioreactor. With increasing duration of backwash, the rate of growth of transmembrane pressure (TMP) gradually increased. The proportions of concentration polarization resistance Rp and cake layer resistance Rf were 48.87% and 50.08%, respectively. Under the action of static electricity, negatively charged particles in the mixed liquid do not easily adhere to the membrane. Under conditions of high mixed liquid suspended solids (＞12 000 mg/L), an increase in the suspended solid content in the mixture caused membrane fouling and pore blockage. When the flux exceeded 58 L·m−2·h−1, the TMP increased sharply. When the aeration rate exceeded 200 mL/min, the impact of membrane erosion on fouling was no longer significant. The optimal suction/cessation ratio was 7:3. After cleaning with NaOH and NaClO, surface fouling of the membrane was significantly reduced.

Pilot study on ceramic flat membrane bioreactor in treatment of coal chemical wastewater

Some toxic and refractory pollutants in coal chemical wastewater can penetrate the biochemical treatment systems and cause high concentrations of suspended solids in the effluent, which may obstruct the subsequent advanced treatment. In this project, a submerged ceramic plate membrane system was integrated to the last oxic corridor of an existing multistage anoxic/oxic tank. In the ceramic flat membrane bioreactor, the influent chemical oxygen demand (COD) was 102.24–178.88 mg/L, with a removal ratio of approximately 30%. The NH3–N concentration in the effluent was relatively stable with an average value of 1.76 mg/L. The turbidity of the effluent was in the range of 0.235–0.852 NTU and was stable below 1 NTU. A flux of 30 L m−2·h−1 could meet the requirements of the pilot test. A gas-water ratio of 50:1 was found optimal. When the concentration of mixed liquor suspended solids (MLSS) was >3769 mg/L, the extracellular polymeric substance in the mixed solution was utilized by microorganisms as a substrate. High MLSS decreased membrane fouling rate. NaClO backwashing can effectively remove pollutants without adversely affecting the treatment efficiency of membrane bioreactors.

Mechanism of organic fouling in the reverse osmosis process of coal chemical wastewater

With the development and utilization of coal on a large scale, the treatment of coal chemical wastewater (CCW) had received extensive attention. This study utilized CCW from a coal liquefaction wastewater treatment plant to investigate the mechanism of organic fouling in the reverse osmosis (RO) process. CCW, which possessed high levels of organic matter, underwent RO process and resulted in significantly improved water quality, with a decrease in total organic carbon from 173.70 mg/L to 2.36 mg/L. However, the membrane surface was fouled by organic matter after continuous filtration for 14 h, causing a substantial reduction in the membrane flux, which decreased to 69.0 % normalized membrane flux. High molecular weight humic acid, the primary organic matter present in CCW, was found to be responsible for the organic fouling on the membrane surface, consistent with the main organic component of CCW. Moreover, organic foulants, including nitrogen heterocyclic compounds, alcohols, and lipids, were detected on the membrane surface. The study presented herein provides a comprehensive understanding and analysis of organic fouling in a RO system, offering crucial data support for the development of effective strategies to prevent and control RO membrane fouling in water treatment processes.

The Catalytic Wet Oxidation of Excess Activated Sludge from a Coal Chemical Wastewater Treatment Process

An improved catalytic wet oxidation method for the disposal of excess activated sludge from a coal chemical wastewater treatment process by using the prepared Cu-Ce/γ-Al2O3 catalyst was reported. The effects of catalyst dosage, reaction temperature and time, and initial oxygen pressure on the degradation of the sludge were investigated. The maximum removal rate of volatile suspended solids, 93.2%, was achieved at 260 °C for 60 min with the catalyst 7.0 g·L−1 and initial oxygen pressure 1.0 MPa. The removal rate of chemical oxygen demand was 78.3% under the same conditions. The production of volatile fatty acids, including mainly acetic acid, propanoic acid, and isobutyric acid, increased with the increasing temperature. These acids have the potential to be carbon sources for the biological treatment of wastewater. Scanning electron microscopy images showed that the sludge became a loose porous structure, which is beneficial for dewatering performance. The results of an energy dispersive spectroscopy analysis illustrated that the carbon element in the sludge substantially migrated from solid to liquid phases. Therefore, these results demonstrated that the proposed catalytic wet oxidation method offers a promising pathway for the disposal and utilization of excess activated sludge from the coal chemical wastewater treatment process.

Novel strategy to enhance the biological treatment of coal chemical wastewater by nano-zero valent ironloaded fly ash-based activated carbonassisted activated sludge process.

Industrial waste as novel conductive mediator was applied for wastewater treatment as a novel strategy for both waste recycling and sustainable development of wastewater treatment. In this study, nanoscale zero valent iron-loaded fly ash-based activated carbon (nZVI@FABAC) was prepared and applied to enhancing activated sludge (AS) process for coal chemical wastewater (CCW) treatment. The results demonstrated that the removal efficiencies of COD and total phenols (TPh) in nZVI@FABAC/AS process reached about 83.96 and 85.17%, which increased 52.51 and 31.52% compared with the single AS process, respectively. And the acute toxic unit value of CCW was reduced by 88.24% after nZVI@FABAC/AS process treatment. The various functional bacteria including phenol-degrading bacteria (Comamonas and Acinetobacter), electroactive bacteria (Geobacter), and iron reduction bacteria (Geothrix) were enriched in the nZVI@FABAC/AS process, which provided various electron transfer pathways to improve the degradation of toxic organics in CCW. Accordingly, nZVI@FABAC/AS process provided a promising and sustainable way for industrial wastewater treatment.

Kinetic modeling and experimental verification of a swirl flocculation-enhanced reactor: A case study of coal chemical wastewater pretreatment

In this study, a swirl flocculation-enhanced reactor (SFR) was designed to address the problems of high dosage and poor pollutant removal in the pretreatment process of coal chemical wastewater (CCW). The effects of different height-to-diameter (H/D) ratios, stirring speed, and impeller length on SFR flow field were analyzed by computational fluid dynamics (CFD) simulation. The optimal H/D and operating condition of SFR were determined by comparing and analyzing fluid velocity, eddy viscosity, and turbulent kinetic energy. Then the lab-scale SFR was manufactured to conduct agglomeration tests. The results showed that the flocculation effect was the best when the H/D ratio of SFR is 8:5 and the mixing blade length was at 3/10 of the reactor as well as 180 r/min of agitating rate. The removal rates of oil, suspended solids (SS), chemical oxygen demand (COD) and phenol in CCW could reach 73.43%, 87.88%, 78.63% and 65.20%, respectively. In addition, the plausibility of SFR design was further validated by the fact that the reagent dose was reduced by 50–60% and the removal rate was increased by 20–30% in comparison with the beaker flocculation experiment. The SFR flow field flocculation enhancement mechanism was analyzed. It is expected that the reactor designed in this work, has a wide range of industrial applications in the CCW treatment.

Microbial metabolism regulation on the efficient degradation of aromatic compounds for biochemical treatment process of coal chemical wastewater in pilot scale

At present, the common problems of biochemical treatment systems of coal chemical wastewater were the poor system stability and the difficulty in reaching COD discharge standards. Aromatic compounds were the main contributors to COD value. The effective removal of aromatic compounds was an urgent problem in the biochemical treatment systems of coal chemical wastewater. In this study, the dominant microbial strains that could degrade phenol, quinoline, and phenanthrene were isolated respectively and inoculated into the pilot scale biochemical tank of coal chemical wastewater. The regulation effect and mechanism of microbial metabolism on the efficient degradation of aromatic compounds were studied. The results indicated that the various aromatic compounds were significantly removed under the regulation of microbial metabolism, the removal efficiencies of COD, TOC, phenols, benzenes, N-CHs, and PAHs were increased by about 25%, 20%, 33%, 25%, 42%, and 45%, respectively, and their biotoxicity was also drastically reduced. Moreover, the abundance and diversity of microbial community, and the microbial activity were obviously improved, as well as the various functional strains were selectively enriched, suggesting that the regulation system could resist environmental stresses with high substrate concentration and toxicity, which could lead to more enhanced performance for aromatic compounds removal. In addition, the microbial EPS content was significantly increased, implying the formation of microbial hydrophobic cell surfaces, which could improve the bioavailability of aromatic compounds. Furthermore, the enzymatic activity analysis revealed that the relative abundance and activity of key enzymes were all obviously improved. In conclusion, multiple lines of evidence were provided to clarify the regulation mechanism of microbial metabolism on the efficient degradation of aromatic compounds for biochemical treatment process of coal chemical wastewater in pilot scale. The results laid a good foundation for realizing the harmless treatment of coal chemical wastewater.

Ball-milled magnetic sludge biochar enables fast aerobic granulation in anoxic/oxic process for the treatment of coal chemical wastewater

Coal chemical wastewater (CCW) containing toxic and hazardous matters requires to be treated prior to discharge. Promoting the in-situ formation of magnetic aerobic granular sludge (mAGS) in continuous flow reactor process has a great potential for CCW remediation. However, long granulation time and low stability limit the application of AGS technology. In this study, Fe3O4/sludge biochar (Fe3O4/SC) with biochar matrix derived from coal chemical sludge were applied to facilitate the aerobic granulation in two-stage continuous flow reactors, containing separated anoxic and oxic reaction units (abbreviated as A/O process). The performance of A/O process was evaluated at various hydraulic retention times (HRTs) (42 h, 27 h, and 15 h). Magnetic Fe3O4/SC with porous structures, high specific surface area (BET = 96.69 m2/g), and abundant functional groups was successfully prepared by ball-milled method. Adding magnetic Fe3O4/SC to A/O process could promote aerobic granulation (85 days) and the removal of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total nitrogen (TN) from CCW at all tested HRTs. Since the formed mAGS had high biomass, good settling ability, and high electrochemical activities, mAGS-based A/O process had high tolerance to the decrease of HRT from 42 h to 15 h for CCW treatment. The optimized HRT for A/O process was 27 h, at which Fe3O4/SC addition can result in the increase of COD, NH4+-N and TN removal efficiencies by 2.5 %, 4.7 % and 10.5 %, respectively. Based on 16S rRNA genes sequencing, the relative abundances of genus Nitrosomonas, Hyphomicrobium/Hydrogenophaga and Gaiella in mAGS accounting for nitrification, denitrification as well as COD removal were increased during aerobic granulation. Overall, this study proved that adding Fe3O4/SC to A/O process was effective for facilitating aerobic granulation and CCW treatment.

Efficiency of submerged ceramic flat membrane bioreactor in the treatment of coal chemical wastewater

Coal chemical wastewater inhibits the development of the modern coal chemical industry. This study used a submerged ceramic flat membrane bioreactor to treat coal chemical wastewater. By combining the characteristics of high flux and high strength of ceramic flat membrane with the characteristics of high sludge concentration of Membrane Bio-Reactor (MBR). The treatment effect of ceramic flat membrane bioreactor on coal chemical wastewater and related influencing factors were studied. The Chemical Oxygen Demand (COD) concentration, ammonia nitrogen concentration, total phenol concentration, and turbidity of coal chemical wastewater could be reduced to below 31.4 mg/L, 3.03 mg/L, 3.76 mg/L, and 0.4 NTU. The ceramic flat membrane bioreactor achieved the optimal removal effect on pollutants when Hydraulic Retention Time (HRT) was 21 h, Dissolved Oxygen (DO) concentration was 3.2–4.0 mg/L and pH was 7.1–7.5. Among them, the total phenol removal ratio reached the maximum value of 95.31 %, and the COD removal ratio remained at 93 % ∼ 94 %, ammonia nitrogen removal ratio was stable at 95 % ∼ 97 %. The microorganisms in the mixture and membrane mainly were aerobic bacteria, and the content of organic-degrading bacteria, nitrifying and denitrifying bacteria was high. The addition of a membrane module not only prevented the loss of activated sludge in the reactor but also kept a high sludge concentration. Meanwhile, the addition of a membrane module also improves the biodiversity and stability of sludge treatment system.

Preparation of Mn/Zn@PG Catalyst for Catalytic Oxidation Treatment of Coal Chemical Wastewater.

In this study, Mn/Zn@palygorskite (PG) catalysts with developed pores and good salt tolerance were prepared and applied to the treatment of coal chemical wastewater. A doping ratio of metal elements, calcination temperature, and calcination time was used to optimize the preparation conditions and determine the optimal preparation conditions of the Mn/Zn@PG catalysts. The catalysts, obtained under various preparation conditions, were characterized and analyzed by XRD, SEM, EDS, BET, XRF, XPS, and other techniques. Results showed that the Zn and Mn elements in the Mn/Zn@PG catalyst existed as ZnO and MnO2, respectively. The optimal working conditions of the Mn/Zn@PG catalyst for catalytic oxidation treatment of coal chemical wastewater, obtained through the optimization of working conditions, are the following: reaction time 60 min, wastewater pH = 9.28, ozone ventilation rate 0.2 L/min, catalyst filling ratio 20%. The height-to-diameter ratio of the tower was 6:1. The abrasion resistance and catalytic performance of the Mn/Zn@PG catalyst after repeated use were investigated, and the mechanism of the loss of active components of the Mn/Zn@PG catalyst was explored. The coal chemical wastewater, before and after treatment, was analyzed by UV–vis spectroscopy and 3D fluorescence spectroscopy. The hierarchical–principal component comprehensive evaluation system (AHP–PCA) was established to evaluate the catalytic ozonation process of coal chemical wastewater, so that the overall evaluation of the process performance can be achieved.

Study on the mechanism of anaerobic fluidized bed microbial fuel cell for coal chemical wastewater treatment.

The coal chemical wastewater (CCW) was treated by anaerobic fluidized bed microbial fuel cell (AFB-MFC) with macroporous adsorptive resin (MAR) as fluidized particle. Isosteric heat calculation and molecular dynamics simulation (MDS) have been performed to study the interaction between organics of CCW and MAR. The isosteric heat of MAR to m-cresol was the largest at 65.4961kJ/mol, followed by phenol. Similarly, the diffusion coefficient of m-cresol on MAR was the largest, which was 0.04350 Å2/ps, and the results were verified by the kinetic adsorption experiments. Microbial community analysis showed that the dominant bacteria in activated sludge of MFC fed with CCW were acinetobacter, aeromonas, pseudomonas and sulfurospirillum. The synergistic cooperation of bacteria contributed to improving CCW degradation and the power generation of MFC. Headspace-gas chromatography-mass spectrometry (HS-GC-MS) was used to detect intermediate of organics in CCW. It was proved that the intermediate of m-cresol degradation was 4-methyl-2-pentanone and acetic acid, and the intermediate of phenol degradation included cyclohexanone, hydroxyhexanedither and hydroxyacetic acid. Combined with the highest occupied molecular orbital (HOMO) analysis results of organic matter obtained by molecular simulation, the degradation pathway of organic matter in CCW was predicted. The energy of organics degradation pathway was analyzed by Materials Studio (MS) software, and the control step of organics degradation was determined.

Deciphering the spatial fouling characteristics of reverse osmosis membranes for coal chemical wastewater treatment

Reverse osmosis (RO) membranes are widely used in the advanced treatment of coal chemical wastewater. Nevertheless, membrane fouling is an intractable concern which decreases permeate flux, impairs water quality and increases energy consumption. Mapping the spatial distribution of membrane fouling and identifying the key factor for flux decline are of great significance for membrane fouling control. In this study, each membrane sample from first-stage and second-stage RO membrane elements was divided into 12 regions for autopsy. The results showed that membrane fouling at both stages was exacerbated from the feed end to the concentrate end owing to the concentrating effect and concentration polarization. Organic and inorganic foulants mainly deposited at the concentrate end and near the permeate tube, whereas biofouling did not show a regular distribution pattern. Biofouling was the paramount contributor to flux decline, whether at the first stage (40%) or the second stage (27%). However, the effect of inorganic fouling became prominent at the second stage due to the higher concentration of inorganic ions and stronger interactions with other foulants. Suggestions for membrane fouling control strategies include reinforced anti-biofouling countermeasures at the lead element, anti-scaling schemes after the first stage, and customized feed spacer and membrane designs for specific fouling at different locations.

Efficiency of Submerged Ceramic Flat Membrane Bioreactor in the Treatment of Coal Chemical Wastewater

Efficiency of Submerged Ceramic Flat Membrane Bioreactor in the Treatment of Coal Chemical Wastewater

Efficiency of Submerged Ceramic Flat Membrane Bioreactor in the Treatment of Coal Chemical Wastewater

Efficiency of Submerged Ceramic Flat Membrane Bioreactor in the Treatment of Coal Chemical Wastewater

Treatment of reverse osmosis concentrate from industrial coal wastewater using an electro-peroxone process with a natural air diffusion electrode

• Electro-peroxone (EP) treated reverse osmosis concentrate (ROC) for the first time. • The use of natural air diffusion electrode in EP was studied for the first time. • EP could remove refractory substances in ROC within 2 h. • The EP process had high tolerance to wastewater quality. • The combination of peroxi-coagulation (PC) and EP outperformed EP. Reverse osmosis concentrate (ROC) produced in the RO treatment of coal chemical wastewater is highly toxic and difficult to degrade. In this study, an electro-peroxone (EP) process was applied to treat ROC with a natural air diffusion electrode (NADE), which was used as the cathode to efficiently generate H 2 O 2 . The treatment efficiency of EP, electro-Fenton, electro-oxidation (EO), peroxi-coagulation (PC) and ozonation for the removal of total organic carbon, colour and UV 254 in ROC were studied and compared, confirming that EP was the most efficient process. The EP process as well as electric energy consumption (EEC) were optimized, and an optimum reaction conditions (current of 200 mA, pH of 4 and O 3 dose of 6 mg/min) were selected. The production of ⋅ OH in EP was much higher than that in ozonation and EO, as indicated by the EPR measurement. Excitation-emission matrix spectra of ROC after EP treatment verified that all the fluorescent contaminants in ROC was removed within 2 h. Further, the combination of PC and EP processes (2 h + 3 h) significantly reduced EEC by 58% as compared with EP (6 h), realizing complete decolouration. This study declared the potential of using EP and the combined PC-EP process to effectively treat the real ROC wastewater.

Pilot-scale treatment of hypersaline coal chemical wastewater with zero liquid discharge

Coal to chemical processes produce substantial quantities of hypersaline organic wastewater. Zero liquid discharge (ZLD) is a strategy designed to minimize the wastewater discharge. Here, a pilot-scale ZLD system, consisting of nanofiltration (NF), disc tube reverse osmosis (DTRO), chemical softening, electro-oxidation (EO) and multiple-effect evaporator/crystallizer, was built for the treatment of coal chemical wastewater. The hybrid ZLD process is capable to treat 72 m3 influent per day and reached about 98% water recovery. First, bivalent and monovalent ions were separated from the raw water by a NF-DTRO process. Then the hardness and organic substances of the wastewater were removed by the chemical softening and the EO techniques. Eventually, industrial-grade salts of Na2SO4 and NaCl were recovered through an evaporator-crystallizer. The total operating cost is estimated to be 2.3 $ m−3 influent. This pilot-scale ZLD system is applicable to the treatment and reuse of hypersaline wastewater. The work will provide insights in large-scale application of the ZLD process for wastewater treatment.