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.

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.

Enhanced ozonation of nitrobenzene in water using natural iron ores: Efficiencies, mechanisms and stability

Natural minerals show potential for catalytic ozonation in industrial wastewater treatment. In this study, the efficiencies and mechanisms of two natural iron ores in catalytic ozonation processes (COPs) for aqueous nitrobenzene degradation were initially investigated. Compared with single ozonation process, the removal of TOC increased by about 60 % and 35 % in COPs with natural magnetite and pyrite, respectively. Both natural magnetite and pyrite could promote O3 decomposition to form hydroxyl radicals and 1O2. But the inner reaction pathways were different. The natural magnetite facilitated O3 decomposition through the Lewis acids and the electron transfer between Fe(II)/Fe(III) on the catalyst surface, while electron transfer was the only pathway for O3 decomposition by natural pyrite. Continuous flow fixed-bed reactor was adopted to provide better simulation of the practical operation conditions, so that the potential of engineering application could be evaluated. The natural magnetite exhibited excellent catalytic activity and stability during long period continuous operation in fixed-bed reactor. The removal of TOC maintained at 81.9 % under the optimized operating parameters of hydraulic retention time (2.84 h), O3 velocity (0.25 L min−1) and O3 concentration (30 mg L−1). HCO3− and PO43− obviously inhibited the TOC removal efficiencies through radical scavenging and surface –OH occupying. While low concentration of Cl− and SO42− showed negligible effect on the mineralization of aqueous nitrobenzene. After the continuous operation for 672 h, the removal of TOC for nitrobenzene solution in the magnetite-COP system was still stable at about 80 %. The present study demonstrated the engineering application prospect of the natural iron ores in catalytic ozonation treatment of recalcitrant chemical wastewaters.

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.

Improving precision and robustness in level control of coupled tank systems: A tree seed optimization and [formula omitted]-analysis approach

Background:Efficient control of liquid levels in interconnected tank systems is a fundamental challenge in various industries, including chemical processes, wastewater treatment, and manufacturing. The traditional approach to achieving precise control has relied on Proportional-Integral-Derivative (PID) controllers, whose performance largely depends on tuned parameters. However, tuning PID controllers for complex and nonlinear systems like coupled tanks remains a challenging task. In recent years, nature-inspired optimization algorithms have gained prominence in control system design. The tree seed optimization (TSO), inspired by the dispersion of tree seeds in search of optimal growth conditions, has shown promise in solving complex optimization problems. This study seeks to explore the application of TSO in tuning PID controllers for coupled tank systems.Methodology:This research employs the TSO to optimize PID controller parameters for enhanced liquid-level control in coupled tank systems. The optimization process involves integrating performance metrics and closed-loop gain constraints to achieve optimal control of coupled tank systems. The imposed constraints aim to ensure robustness and system stability in the face of uncertainties and disturbances. Besides, μ analysis quantifies the robustness of the system by assessing its ability to tolerate uncertainties.Findings:Simulation studies conducted in this research verify the efficacy of the proposed TSO-based approach for tuning PID controllers in coupled tank systems. Compared with various methods, the TSO consistently yields better control performance, reduces settling time, and minimizes overshoot. The robustness of the optimized controllers is also evaluated, showing the ability to handle varying operating conditions effectively.

Study on treatment of chemical plant wastewater by using a integrated anaerobic–aerobic bioreactor

ABSTRACT In this work, a new type of integrated anaerobic aerobic bioreactor (IAAB) was formed by optimizing the structure of the anaerobic baffle bioreactor and aerobic biological contact oxidation pool. IAAB was used to treat the production wastewater of a chemical plant. The whole process was divided into two stages of domestication and stable operation. With increasing the proportion of chemical wastewater, the total amount of extracellular polymeric substances increased, and the ratio of protein to polysaccharide decreased. Dehydrogenase activity of anaerobic granular sludge in each compartment increased about 1.5 times with time, and decreased about 42% along the flow direction from the first compartment to the third compartment. The coenzyme F420 increased about 4 times with time, and increased about 1.2 times along the flow direction. The IAAB showed excellent removal rate of chemical oxygen demand (85%), ammonia nitrogen (94%), nitrobenzenes (98%).

Visualizing and Evaluating Microbubbles in Multiphase Flow Applications

Accurate visualization of bubbles in multiphase flow is a crucial aspect of modeling heat transfer, mixing, and turbulence processes. It has many applications, including chemical processes, wastewater treatment, and aquaculture. A new software, Flow_Vis, based on experimental data visualization, has been developed to visualize the movement and size distribution of bubbles within multiphase flow. Images and videos recorded from an experimental rig designed to generate microbubbles were analyzed using the new software. The bubbles in the fluid were examined and found to move with different velocities due to their varying sizes. The software was used to measure bubble size distributions, and the obtained results were compared with experimental measurements, showing reasonable accuracy. The velocity measurements were also compared with literature values and found to be equally accurate.

Progress of Electrocatalytic Technology in Treating Organic Chemical Wastewater

In recent years, extensive research has been conducted on the preparation of high catalytic performance electrodes and the development of electrocatalytic water treatment processes. This article introduces the basic principles of electrochemical water treatment, the preparation of electrode materials, and the research progress of electrocatalytic technology for degrading organic chemical wastewater. It analyzes the problems faced by electrocatalytic degradation of organic chemical wastewater and looks forward to the development trend of electrocatalytic technology in the field of organic chemical wastewater treatment.

Electrocatalytic mechanism of titanium-based anodes and research progress of chemical saline wastewater treatment: A short review

Electrocatalytic treatment of chemical saline wastewater showed great technical advantages due to its characteristics of simple operation, high catalytic efficiency and little secondary pollution. The review takes the classification and composition of titanium-based anodes as the starting point. Typical studies of wastewater treatment by electrocatalytic technology based on free radicals and non-free radicals were also discussed. Combined with the previous researches about electrocatalytic mechanisms in recent years, the mechanisms of titanium-based anodes were analyzed in terms of ·OH, active chlorine and others. The studies on titanium-based anodes in chemical wastewater containing different salt concentrations, such as dye wastewater, coal chemical wastewater, landfill leachate wastewater, fertilizer and pesticide production wastewater, etc., were thoroughly examined. According to the amount of electricity required for the removal of organic matter per unit, the energy consumption of titanium-based anodes for wastewater treatment by electrochemistry was described. The review would provide theoretical basis and technical support for electrocatalytic treatment of chemical saline wastewater.

Development of Management Systems for Sustainable Municipal Waste Management Systems

Waste Management Systems. are designed to efficiently handle and process waste materials generated by human activities. These systems are crucial for minimizing environmental impacts, promoting sustainability, and protecting throughout its lifecycle, from its generation to its final disposal or recycling. Here is an overview of the key components and processes involved in waste management: Waste Generation: Waste can be generated from various sources, including residential areas, commercial establishments, industries, and construction sites. It encompasses solid waste (such as household waste and packaging materials), liquid waste (such as wastewater and sewage), and hazardous waste (such as chemicals and medical waste). Waste Collection: its source. This involves the placement of collection bins or containers at strategic locations, regular pick-up schedules, and specialized collection vehicles for different types of waste. Waste Segregation: After collection, waste is often sorted and segregated based on its type and characteristics. This helps in the efficient management of different waste streams, enabling appropriate treatment or disposal methods. Segregation can be done at the source (e.g., separating recyclables from non-recyclables) or at dedicated facilities. Future vehicular organizations are supposed to send more limited distances the car employer. Client-server methods revel in decrease execution regardless of standard abnormal network. Another one the worldview of shared content dispersion over the Web is arising with swarm conventions. The objective of Web amassing conventions is to lessen the heap on satisfied servers. Waste Treatment: Waste treatment involves various processes aimed at reducing the volume and toxicity of waste, as well as recovering valuable resources. Common treatment methods include composting, incineration, landfilling, and biological or chemical treatment of wastewater. Advanced technologies, such as anaerobic digestion and plasma gasification, are also used for waste conversion. Recycling and Resource Recovery: Recycling plays a crucial role in waste management systems. Materials like paper, plastics, glass, metals, and electronic waste can be recycled and sent to landfills or incinerators. Resource recovery also involves the extraction of energy from waste, such as through waste-to-energy (WTE) facilities. GWP Uppsala WMS,GWP Uppsala CS, GWP Alvdalen WMS, GWP Alvdalen CS, AP Uppsala WMS. IncAll, Inc90%, BioBus, RecPl. From the result it is seen that GWP Uppsala CSis got the first rank where as is the GWP Alvdalen CSis having the lowest rank. GWP Uppsala CSis ranked first and industrial building is ranked lowest.

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.

Biodegradability enhancement and sequential treatment of real chemical industry wastewater by chemical coagulation and Electro-Fenton processes

A sequential treatment with chemical coagulation in the first step and Electro-Fenton (EF) in the second step was applied to chemical industry wastewater. By coagulation using Poly Aluminum Chloride (PAC) as a coagulant, 57.5% chemical oxygen demand (COD), 96.8% total suspended solids (TSS), and 90.5% color index (CI) removal were obtained. In the EF process applied after chemical coagulation, the design parameters were optimized by the central composite design. Two quadratic models of the four factors were established with the COD and CI as two responses. Optimized conditions of the EF were pH 2.5, Fe2+ dose 5 mM, applied current 1 A, and reaction time 60 min. Under these conditions, the COD removal from the validation experiments was 63.5%. In total, 84.5% COD removal was achieved with the two-step treatment. By extending the reaction time in EF to ensure the discharge limits, 89.5% COD removal was reached, and the COD concentration decreased to 193 mg/L after 240 min. At the same time, the 5-day biochemical oxygen demand (BOD5)/COD ratio increased from 0.1 to 0.57 after 240 min. Consequently, the discharge limit was provided and the biodegradability was improved.

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.

Floodplain lakes as an indicator of increasing industrial pollution – Case study from a fertilizer factory in Poland

Despite the development of organic farming, the demand for mineral fertilizers is still high. Processes of fertilizer production are water-consuming, which is why factories are often located near large rivers. Such facilities should be monitored in detail because they might pose a threat to water quality. The aim of this study was to analyse the impact of a nitrogen fertilizer factory chemical wastewater treatment plant (CWTP) on the water quality of nearby river-lake systems. Potential contamination could indicate installation defects. Six floodplain lakes were selected for analysis: three located within the embanked area and three outside the embanked area, all close to the CWTP. Two similar lakes 30 km upstream were chosen as controls. Water samples were taken monthly from March to November 2022. We analysed pH, electrical conductivity (EC), the content of Cl−, total nitrogen (TN), NH4+, NO3−, total phosphorus (TP), PO43−, dissolved organic carbon (DOC), Ca2+, K+, Mg2+ and Na+. Statistical analysis indicated that the canal that drains, among others, the cooling towers wastewater, might have an impact on the nearby lakes, significantly increasing their content of Cl− and Na+. On the other hand, the concentration of NH4+ was significantly higher in the lakes located downstream of the CWTP, although they did not have any surface connection with the CWTP reservoir. This fact and NH4+-polluted water seeping under the dike indicate that the CWTP reservoir might be leaking. Further research on underground water is required to establish whether the CWTP reservoir is properly secured. It is extremely important because the CWTP is located in the Vistula River valley, which supplies drinking water to almost 2 mln people. Any damage to the reservoir, e.g., during a flood, would lead to an ecological disaster involving not only the Vistula but also the Baltic Sea, affecting millions of people.

Mesoporous PdO–loaded WO3 nanocrystals: A promising photocatalyst for highly efficient photoreduction of nitrobenzene to aniline under visible light

BackgroundNitrobenzene (NTB) conversion to aniline (AN) is a key technology for large-scale industrial chemical production and wastewater treatment. Accordingly, photocatalytic reduction of nitrobenzene has emerged as a green technology to produce aniline. MethodsThis study offers a simple nontoxic surfactant-assisted fabrication of mesoporous tungsten oxide (WO3) nanostructures accompanied by the incorporation of tiny contents (0.5‒2.0 wt%) of palladium oxide (PdO) nanoparticles through impregnation and calcination. Significant findingsPhysicochemical investigations of fabricated heterostructures revealed the formation of mesoporous surfaces and showed the implication of PdO loading on textural and optoelectronic characteristics of WO3. Only 2.0 wt% PdO on the WO3 surface caused a notable decline in the energy bandgap from 2.77 to 1.07 eV, confirming visible light-harvesting improvement. The prepared PdO–loaded WO3 was examined for NTB photoreduction to AN. The optimum content of 1.5 wt% PdO/WO3 (2.0 g L–1) exhibited a complete phototransformation of NTB to AN after only 40 min with excellent reusability and recyclability. The PdO loading significantly facilitated photoinduced charge carriers’ separation and mobility through the construction of Step (S)-scheme heterojunction. This work opens the door for developing semiconductor-based photocatalysis as a green process for effectively converting contaminated water into useful value-added chemicals.

Dynamics of bubbles detached from non-circular orifices: Confinement effect of orifice boundary

In practice, gas usually escapes from non-circular orifices due to machining accuracy, plugging, and other reasons, especially gas leakage in the natural environment. Compared to circular orifices, the bubble behavior and dynamics of non-circular orifices have rarely been investigated. This paper presents three-dimensional imaging system results to obtain comprehensive information on bubble dynamics generated from five elliptical orifices with equal cross-sectional areas and different aspect ratios. Computational fluid dynamics studies using the coupled level set and volume of fluid methods were adopted to assist in the flow field analysis. Experimental data were analyzed statistically to study the effects of orifice wall structure on bubble flow pattern, size, trajectory, and other dynamic parameters. The results show that the equivalent bubble diameter increases with increasing orifice aspect ratio, as does the randomness of the bubble flow field, while the bubble flow pattern complexity increases. A force analysis as the bubble is generated is also conducted. The wall structure of the orifice affects the bubble migration effect to some extent. The work presented in this article provides valuable fundamental information for a range of heater and desalination applications in chemical engineering, wastewater treatment, and immersion leakage identification.

Membrane distillation with electrospun omniphobic membrane for treatment of hypersaline chemical industry wastewater

Hypersaline chemical industry wastewater comprises various species with complex characteristics, challenging the proposal treatment of such wastewater. Membrane distillation (MD) is a promising technology to realize the zero liquid discharge treatment of wastewater, due to its high salt rejection and insensitivity to the feed concentration. However, the practical application of the MD process is hindered by membrane wetting and fouling issues. Herein, we developed an innovative strategy to fabricate a robust omniphobic membrane via bio-inspired silicification and fluorosilanization on an electrospun poly(vinylidene fluoride-co-hexafluoropropylene) nanofiber mat. The polydopamine/polyethylenimine (PDA/PEI) deposition time was optimized based on the results of membrane morphology, wettability, and pore structure measurements. The MD process achieved a stable flux using the omniphobic membrane even when treating feed solution containing sodium dodecyl sulfate (SDS). In addition, the omniphobic membrane significantly outperformed the pristine membrane in treating hypersaline chemical industry wastewater. This work provides a novel method for fabricating robust electrospun omniphobic membranes for high-performance treatment of hypersaline chemical industry wastewater via the MD process.