Search Results (39)

Low-cost powdered activated coke (PAC) produced by a one-step rapid method with lignite was used as an adsorbent for the advanced treatment of phenol-containing wastewater to evaluate the feasibility of replacing high-cost commercial powdered activated carbon. Characterization using infrared spectral analysis, SEM, and BET showed that the PAC mesopores were well developed. PAC exhibited a high adsorption performance for phenol in static experiments. The adsorption was almost in equilibrium within 20 min, and the removal efficiency reached 85.4% with 1.5 g L⁻¹ PAC and 99.9% with 4 g L⁻¹ PAC. As common components in wastewater, NaCl and Na₂SO₄ did not exhibit significant competitive adsorption with phenol in PAC. The adsorption process occurred in accordance with the Langmuir model and the pseudo-second order kinetic model. Furthermore, the effects of hydrothermal regeneration on PAC adsorbing phenol were studied, and the adsorption capacity of PAC after five regeneration cycles was 86.1% of that of the new PAC, which still had good adsorption performance. PAC offers significant advantages in terms of adsorption capacity, economic feasibility, regeneration, and recycling, providing a practical solution to the problem of phenol-containing wastewater pollution. Full article

The discharge of organic and inorganic nitrogenous pollutants in wastewater leads to eutrophication and disrupts the ecological balance. Therefore, the pressing need for an effective treatment method has become increasingly evident. A robust bacterium Pseudomonas stutzeri H3 capable of simultaneous organic and inorganic nitrogen removal was isolated from the activated sludge in the coking wastewater treatment system. The optimal conditions for the simultaneous removal of ammonium nitrogen and quinoline were as follows: C/N ratio of 15–20, initial pH of 7–8, culture temperature of 30 °C, and shaking speed of 150–300 rpm. At 200 mg/L ammonium nitrogen and 100 mg/L quinoline, strain H3 achieved above 90% of removal efficiency, exhibiting excellent simultaneous nitrogen removal capabilities. The outstanding nitrogen removal efficiencies in the presence of quinoline and different inorganic nitrogen sources further confirmed the simultaneous organic and inorganic nitrogen removal capability of strain H3. The whole genome sequencing and nitrogen metabolic intermediates determination of strain H3 were performed to elucidate the gene function annotations, nitrogen removal function genes, and nitrogen metabolic pathways. The findings provide a promising pathway to treat the organic and inorganic nitrogenous pollutants in wastewater. Full article

The aim of the work was to investigate the treatment efficiency of coking wastewater in a hybrid system combining the Fenton process with an SBR reactor. The Fenton reaction was optimised using variable reagent doses of 0.75, 1.0, 1.25 and 1.5 g/L for iron ions and 750, 1000, 1250, and 1500 mg/L for H₂O₂. The effects of Fe²⁺ and H₂O₂ concentration on BOD, COD, TOC, TN N-NH₄⁺ and BOD/COD ratio were studied in detail to optimise the pretreatment performance. The selection of the most favourable parameters for the Fenton reaction was based on the frequency of occurrence of a different combination of the chemical reagents. The most beneficial doses were found to be 0.75 g/L of iron (II) ion and 1000 mg/L of hydrogen peroxide, at which the COD reduction rate was about 40% and a high increase in the BOD₅/COD ratio from 0.1 to 0.31 was observed. Moreover, the obtained results showed that the efficiency of removing organic pollutants and nitrogen compounds was higher in the SBR reactor fed with pretreated wastewater. However, the relatively low efficiency of removing TKN (25%) and NH₄⁺ (21%) indicates the presence of toxic substances in them that may inhibit the removal of nitrogen compounds. Full article

This study explores the enhanced removal of refractory organic compounds from coking wastewater using polyaluminum chloride (PACl) with two different basicity levels (0.5 and 2.5), in combination with coagulant aids such as cationic polyacrylamide (CPAM) and iron ions. The results demonstrated that both PACl formulations significantly outperformed commercial PACl in terms of COD and color removal, with PACl at the basicity of 2.5 achieving slightly higher efficiency than PACl at the basicity of 0.5. The improved performance was attributed to the higher content of polymeric aluminum species, enhancing charge neutralization and bridging adsorption. The addition of coagulant aids further improved the performance, with PACl at the basicity of 2.5 combined with iron ions achieving the highest COD (48.41%) and color removal (80.77%), due to sweep coagulation and complexation. Organic composition analysis using gas chromatography–mass spectrometry (GC-MS), three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy, and ultraviolet (UV) spectroscopy indicated that PACl combined with iron ions was the most effective in removing polycyclic aromatic hydrocarbons (PAHs) and nitrogen-, oxygen-, and sulfur-containing heterocyclic compounds. Additionally, a floc analysis showed that the flocs formed with iron ions were more compact and had better settleability compared to those formed with CPAM, further contributing to the improved coagulation efficiency. These results highlight the importance of optimizing the PACl basicity and coagulant aid selection for the enhanced removal of refractory organic compounds from coking wastewater, offering a promising strategy for advanced wastewater treatment. Full article

This review examines the technological bottlenecks, potential solutions, and future development directions in the treatment and resource utilization of semi-coking wastewater (SCOW) in China. By comprehensively investigating the semi-coking industry and analyzing wastewater treatment research hotspots and existing projects, this study systematically explores the current status and challenges of each treatment unit, emphasizing the necessity for innovative wastewater treatment technologies that offer high efficiency, engineering feasibility, environmental friendliness, and effective resource recovery. This review highlights prospects and recommendations, including the development of novel extractants for phenol and ammonia recovery, a deeper understanding of biological enhancement mechanisms, exogenous bio-enhancement materials, and the creation of cost-effective advanced oxidation process (AOP)-based combined processes. Additionally, it underscores the potential for repurposing SCOW as a valuable resource through appropriate treatment, whether recycling for production or other applications. Full article

The anaerobic-anoxic-oxic (AAO) process is one of the most widely used processes for treating industrial organic wastewater, and it has shown significant effectiveness in the removal of organic compounds, as well as denitrification and phosphorus removal. However, for the treatment of industrial organic wastewater, this anaerobic preposition and aerobic postposition process has exposed various limitations. Therefore, for this type of wastewater, the oxic-hydrolytic and denitrification-oxic (OHO) treatment process has been proposed and developed based on the principles of three-sludge separation and fluidization. This study integrated operational data from 203 coking wastewater treatment plants worldwide, and the two-step nitrification-denitrification activated sludge model No.3 (TCW-ASM3) was used for comparative analysis of the pollutant removal efficiency and total operating cost of the AAO process and the OHO process in the face of characteristic pollutants in coking wastewater. The results indicate that the full-scale OHO process achieved removal efficiencies of up to 3784 mg/L for chemical oxygen demand (COD) and 297 mg/L for total nitrogen (TN). The theoretical total cost for OHO and AAO were 9.75 and 14.38 CNY/m³, respectively. The pre-treatment aerobic process effectively reduces the biological toxicity of high-toxicity and refractory industrial wastewater, and the three-sludge system provides a stable living space for functional microorganisms, the combination of multi-mode denitrification processes offers new possibilities for treating similar types of industrial wastewater. Full article

It is very important to choose a suitable method and catalyst to treat coking wastewater. In this study, Fe–Ce–Al/MMT catalysts with different Fe/Ce molar ratios were prepared, characterized by XRD, SEM, and N₂ adsorption/desorption, and treated with coking wastewater. The results showed that the optimal Fe–Ce–Al/MMT catalyst with a molar ratio of Fe/Ce of 7/3 has larger interlayer spacing, specific surface area, and pore volume. Based on the composition analysis of real coking wastewater and the study of phenol simulated wastewater, the response surface test of the best catalyst for real coking wastewater was carried out, and the results are as follows: initial pH 3.46, H₂O₂ dosage 19.02 mL/L, Fe²⁺ dosage 5475.39 mL/L, reaction temperature 60 °C, and reaction time 248.14 min. Under these conditions, the COD removal rate was 86.23%. Full article

Effective and economical processes for the advanced treatment of coking wastewater were urgently needed to reduce the persistent organic pollutants of external drainage. In the present work, we investigated the degradation of organic pollutants in coking wastewater through IHC/FO (imping stream hydrodynamic cavitation (IHC) coupled with the Fenton oxidation (FO) process) and IHC alone for their feasibility in the advanced treatment of coking wastewater. To select the optimum parameters, attention was paid to the effects of main operation conditions including inlet fluid pressure, medium temperature, initial pH, reaction time, and initial Fe(II) and initial H₂O₂ concentrations. The results showed that the effects of conditions that need energy to be maintained (such as initial pH and inlet pressure) on the organic pollutant removal efficiency through IHC/FO were less pronounced than those through IHC alone. Moreover, the application of IHC/FO could remove more organic pollutants from coking wastewater than IHC even at an energy-efficient condition. For example, the highest COD removal efficiency of 12.5% was achieved in the IHC treatment at 0.4 MPa, pH 3, and 60 min for the reaction time. In the case of IHC/FO, the maximum COD removal of 33.2% was obtained at pH 7, 0.1 MPa, 12 mmol/L H₂O₂, and 3 mmol/L Fe²⁺ after reacting for 15 min. The ultraviolet and visible spectrophotometry (UV-Vis) absorption spectra and gas chromatography and mass spectrometry (GC–MS) analysis further revealed that the kinds and amounts of pollutants (especially those that had benzenes) remaining in water treated through IHC/FO were much fewer and smaller than in water treated through IHC alone. The better performances of IHC/FO than IHC alone were likely related to the more hydroxyl radicals produced through IHC/FO. Taken together, our findings indicate that IHC/FO has great application potential in the advanced treatment of coking wastewater. Full article

This study primarily focused on the efficient transformation of low-priced blue coke powder into a high-capacity adsorbent and aimed to address the pollution issue of hexavalent chromium (Cr (VI))-laden wastewater and to facilitate the effective utilization of blue coke powder. A two-step method was utilized to fabricate a blue coke-based nitric acid-modified material (LCN), and the impact of nitric acid modification on the material’s structure and its efficacy in treating Cr (VI)-contaminated wastewater was evaluated. Our experimental results illustrated that, under identical conditions, LCN exhibited superior performance for Cr (VI) treatment compared to the method employing only potassium hydroxide (LCK). The specific surface area and pore volume of LCN were 1.39 and 1.36 times greater than those of LCK, respectively. Further chemical composition analysis revealed that the functional group structure on the LCN surface was more conducive to Cr (VI) adsorption. The highest amount of Cr (VI) that LCN could bind was measured at 181.962 mg/g at 318 K. This was mostly due to chemisorption, which is dominated by redox reactions. The Cr (VI) removal process by LCN was identified to be a spontaneous, exothermic, and entropy-increasing process. Several tests on recycling and reuse showed that LCN is a stable and effective chromium-containing wastewater adsorbent, showing that it could be used in many situations. Full article

The treatment and reuse of wastewater are crucial for the effective utilization and protection of global water resources. Polycyclic aromatic hydrocarbons (PAHs), as one of the most common organic pollutants in industrial wastewater, are difficult to remove due to their relatively low solubility and bioavailability in the water environment. However, biosurfactants with both hydrophilic and hydrophobic groups are effective in overcoming these difficulties. Therefore, a biosurfactant-producing strain Pseudomonas mosselii MP-6 was isolated in this study to enhance the bioavailability and biodegradation of PAHs, especially high-molecular-weight PAHs (HMW-PAHs). FTIR and LC-MS analysis showed that the MP-6 surfactant belongs to rhamnolipids, a type of biopolymer, which can reduce the water surface tension from 73.20 mN/m to 30.61 mN/m at a critical micelle concentration (CMC = 93.17 mg/L). The enhanced solubilization and biodegradation of PAHs, particularly HMW-PAHs (when MP-6 was introduced), were also demonstrated in experiments. Furthermore, comprehensive environmental stress tolerance tests were conducted to confirm the robustness of the MP-6 biosurfactant, which signifies the potential adaptability and applicability of this biosurfactant in diverse environmental remediation scenarios. The results of this study, therefore, have significant implications for future applications in the treatment of wastewater containing HMW-PAHs, such as coking wastewater. Full article

The effluent of coking wastewater comprises hundreds of refractory organics and is characterized by high toxicity and non-biodegradation. Electrochemical advanced oxidation processes (EAOPs) have been widely applied in the field of water purification. In this study, a Ti₄O₇ reactive electrochemical membrane (REM) was prepared using the plasma spraying method for the electro-oxidation of coking wastewater. The composition and surface morphology of the Ti₄O₇ REM were characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The computational fluid dynamics (CFD) simulation was used to compare the mass transfer performance of the Ti₄O₇ REM in traditional batch (TB) mode and flow-through (FT) mode. In the FT mode, the effects of current density and anode–cathode distance on the treatment efficiency were investigated, and the electrocatalytic performance of the anode on coking wastewater was analyzed. The results showed that the COD removal efficiency reached 76.2% with an energy consumption of 110.5 kWh kg⁻¹ COD under the optimal condition. In addition, cathodic polarization provides an effective technique for maintaining the long-term activity of the Ti₄O₇ REM. The three-dimensional fluorescence results and UV-vis spectrum showed that the aromatic compounds could be effectively degraded using the Ti₄O₇ REM. The Ti₄O₇ REM demonstrated excellent performance of electrochemical oxidation and satisfactory stability, which had a strong potential for application in the field of practical wastewater and engineering practices that respond to the concept of sustainable development. Full article

A novel coking wastewater treatment technique is proposed based on the principles of the circular economy. By utilizing coal as an adsorbent for organic pollutants in coking wastewater, the treated coal can be introduced into the coking system after the adsorption and flocculation sedimentation processes. This creates a closed-loop system with zero coking wastewater emissions. We investigated the potential of adsorption for the removal of pyridine. Batch experiments were conducted using lignite, coking coal, and anthracite as adsorbents. Both coking coal and anthracite showed favorable adsorption properties for the chosen contaminants. The experimental data were analyzed utilizing various models, including pseudo-first-order and pseudo-second-order kinetic equations, as well as intraparticle diffusion and Bangham. This study aimed to identify the rate-limiting step in the adsorption process. The results revealed that the adsorption of pyridine onto the three coal types followed pseudo-second-order kinetics. The rate-limiting mechanisms may include both boundary-layer diffusion and intraparticle diffusion. The effect of pH on coal adsorption and the activation energy of pyridine adsorption by coking coal were also examined. Adsorption offers a promising approach in advanced wastewater treatment, with coking coal emerging as a cost-effective adsorbent for addressing persistent organic pollutants during the adsorption process. Full article

Hydrogen as an energy vector is going to play an important role in the global energy mix. On the other hand, wastewater management has become a worldwide concern, as urban settlements have been considerably increasing for decades. Consequently, biodigestion to produce biogas (rich in methane) in water treatment plants could be an interesting starting point to obtain a valuable gas that can be converted into hydrogen through steam reforming. The aim of this work was to review the main aspects concerning steam reforming of biogas from wastewater treatment plants. For this purpose, the whole chain, from water treatment to hydrogen production and purification, was considered, paying attention to the main challenges and new technologies for its optimization. Thus, a wide range of possibilities is offered, from direct energy use of syngas to high purification of hydrogen (mainly through pressure swing adsorption or membrane reactors), presenting advantages and disadvantages. In any case, the role of catalysts seems to be essential, and aspects such as hydrogen sulfide and coke deposition control should be addressed. In conclusion, biogas steam reforming applied to wastewater treatment plants is a reality, with serious possibilities for its global implementation at the industrial level, according to techno-economic assessment. Full article

Coking wastewater is a typical high-strength organic wastewater, for which it is difficult to meet discharging standards with a single biological treatment. In this study, effective advanced treatment of coking wastewater was achieved by coagulation with freshly prepared polyaluminum silicate sulfate (PASS). The performance advantage was determined through comparison with commercial coagulants including ferric chloride, polyferric sulfate, aluminum sulfate and polyaluminum chloride. Both single-factor and Taguchi experiments were conducted to determine the optimal conditions for coagulation with COD_Cr and UV₂₅₄ as indicators. A dosage of 7 mmol/L PASS, flocculation velocity of 75 r/min, flocculation time of 30 min, pH of 7, and temperature of 20 °C could decrease the COD_Cr concentration from 196.67 mg/L to 59.94 mg/L. Enhanced coagulation could further help to remove the organic compounds, including pre-oxidation with ozonation, adsorption with activated carbon, assistant coagulation with polyacrylamide and secondary coagulation. UV spectrum scanning and gas chromatography-mass spectrometry revealed that the coagulation process effectively removed the majority of organic compounds, especially the high molecular weight alkanes and heterocyclic compounds. Coagulation with PASS provides an effective alternative for the advanced treatment of coking wastewater. Full article

We analyzed the soil at the site of a former coking wastewater treatment plant on redeveloped land in Taiyuan, northern China, in an attempt to detect the presence of 16 types of priority polycyclic aromatic hydrocarbons (PAHs) listed by the United States Environmental Protection Agency (US EPA) and evaluate the potential pollution risks. The results show that the total proportion of PAHs in the surface soil of the redeveloped land ranged from 0.3 to 1092.57 mg/kg, with an average value of 218.5 mg/kg, mainly consisting of high-ring (5–6 rings) components. Characteristic ratio analysis indicated that the pollution was mainly related to the combustion of petroleum, coal, and biomasses. The wastewater treatment units operated according to the following treatment train: advection oil separation tank, dissolved air flotation tank, aerobic tank, secondary sedimentation tank, and sludge concentration tank. Our study found that pollution resulting from low-ring PAHs mainly appeared in the advection oil separation tank during the pre-wastewater treatment stage, while medium-ring PAH contamination mainly occurred in the dissolved air floatation tank, aerobic tank, and secondary sedimentation tank during the middle stages of wastewater treatment. High-ring PAH contamination primarily appeared in the sludge concentration tank in the latter stage of wastewater treatment. Based on our assessment of the ecological risk using the Nemerow Comprehensive Pollution Index and the toxicity equivalent factor (TEF) method, we determined that individual PAHs in the study area exceeded acceptable levels and the total amount of pollution was potentially harmful to the ecological environment. In addition, the comprehensive lifetime cancer risk for different populations resulting from exposure to the soil in the study area was determined to be within acceptable limits based on the average PAH concentrations. Full article