Coal Chemical Wastewater Treatment Research Articles

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.

Preparation of Supported Perovskite Catalyst to Purify Membrane Concentrate of Coal Chemical Wastewater in UV-Catalytic Wet Hydrogen Peroxide Oxidation System.

The effective treatment of membrane concentrate is a major technical challenge faced by the new coal chemical industry. In this study, a supported perovskite catalyst LaCoO3/X was prepared by a sol–impregnation two-step method. The feasibility of the supported perovskite catalyst LaCoO3/X in the UV-catalytic wet hydrogen peroxide oxidation (UV-CWPO) system for the purification of concentrated liquid of coal chemical wastewater was investigated. The effects of catalyst support, calcination temperature, calcination time, and re-use time on catalytic performance were investigated by batch experiments. The catalysts were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), and X-ray photoelectron spectroscopy (XPS). Experimental results showed that the supported perovskite catalyst LaCoO3/CeO2 prepared using CeO2 as support, calcination temperature of 800 °C, and calcination time of 8 h had the best catalytic effect. The catalytic performance of the catalyst remained excellent after seven cycles. The best prepared catalyst was used in UV-CWPO of coal chemical wastewater membrane concentrate. The effects of H2O2 dosage, reaction temperature, reaction pressure, and catalyst dosage on UV-CWPO were determined. Under the conditions of H2O2 dosage of 40 mM, reaction temperature of 120 °C, reaction pressure of 0.5 MPa, catalyst dosage of 1 g/L, pH of 3, and reaction time of 60 min, the removal efficiencies of COD, TOC, and UV254 were 89.7%, 84.6%, and 98.1%, respectively. Under the optimal operating conditions, the oxidized effluent changed from high toxicity to non-toxicity, the BOD5/COD increased from 0.02 to 0.412, and the biodegradability of the oxidized effluent was greatly improved. The catalyst has a simple synthesis procedure, excellent catalytic performance, and great potential in the practical application of coal chemical wastewater treatment.

Refractory organic compounds in coal chemical wastewater treatment by catalytic ozonation using Mn-Cu-Ce/Al2O3.

A composite Mn-Cu-Ce tri-metal oxide supported on γ-Al2O3 (Mn-Cu-Ce/Al2O3) catalyst was prepared by an impregnation-calcination method and investigated in the catalytic ozonation treatment of real coal chemical wastewater (CCW). The catalyst was characterized by XRD, SEM, TEM, XRF, BET, and XPS techniques. The results showed that Mn, Cu, and Ce metal oxides were evenly distributed on the Al2O3 surface and the catalyst maintained a large surface area and a high pore volume compared with the pristine Al2O3. The synergy between Mn, Cu, and Ce oxides greatly enriched the catalytic active sites and enhanced the ozonation performance. The catalytic ozonation process with Mn-Cu-Ce/Al2O3 increased the removal rate of total organic carbon (TOC) by 31.6% compared with ozonation alone. The ketones, aromatic compounds, phenols, and nitrogen-containing heterocyclic compounds in CCW have been effectively degraded and mineralized by Mn-Cu-Ce/Al2O3 catalytic ozonation process, and its biodegradability has also been significantly improved. The experimental results of ∙OH scavengers revealed that the mechanism of Mn-Cu-Ce/Al2O3 catalytic ozonation was to promote the generation of ∙OH radicals. The catalytic activity of Mn-Cu-Ce/Al2O3 was only a slight decrease in six consecutive catalytic ozonation treatments, showing good stability. Therefore, Mn-Cu-Ce/Al2O3 can be used as a candidate catalyst for the advanced treatment of refractory organic wastewaters upon catalytic ozonation.

An integrated membrane- and thermal-based system for coal chemical wastewater treatment with near-zero liquid discharge

The coal chemical industry consumes and discharges huge volumes of water, with the subsequent treatment and use of this wastewater presenting a great challenge. Near-zero liquid discharge (Near-ZLD) is an efficient technology that supports wastewater reuse and helps to manage shortages in freshwater resources. Near-ZLD is an integrated process combing scaling ion removal, filtration/concentration and evaporation/drying, with the feasibility of this system verified in an engineering case-study (500 m3/h) in China. A combination of coagulation and ion exchange can effectively remove Mg2+and Ca2+ from wastewater, achieving total removal rates of 99.96% and 99.97%, respectively. A combined process of filtration and ultrafiltration can effectively reduce the final turbidity of treated wastewater to below 0.1 NTU. Coupled nanofiltration and evaporation units can achieve effectively terminal wastewater treatment, separating and removing NaCl. Reclaimed water can be recycled with the integrated process, thus achieving near-ZLD, demonstrating high stability and providing an environmentally friendly and sustainable approach for the treatment and reuse of hypersaline coal chemical wastewater.

煤化工废水处理的研究进展

煤化工废水处理的研究进展

Synthesis and evaluation of cationic flocculant P(DAC-PAPTAC-AM) for flocculation of coal chemical wastewater

In this study, a high-efficiency cationic flocculant, P(DAC-MAPTAC-AM), was successfully prepared using UV-induced polymerization technology. The monomer Acrylamide (AM): Acryloxyethyl Trimethyl ammonium chloride (DAC): methacrylamido propyl trimethyl ammonium chloride (MAPTAC) ratio, monomer concentration, photoinitiator concentration, urea content, and cationic monomer DAC:MAPTAC ratio, light time, and power of high-pressure mercury lamp were studied. The characteristic groups, characteristic diffraction peaks, and characteristic proton peaks of P(DAC-MAPTAC-AM) were confirmed by fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), 1H nuclear magnetic resonance spectrometer (1H NMR), and scanning electron microscopy (SEM). The effects of dosage, pH value, and velocity gradient (G) value on the removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol by poly aluminum ferric chloride (PAFC), P(DAC-MAPTAC-AM), and PAFC/P(DAC-MAPTAC-AM) in the flocculation treatment of coal chemical wastewater were investigated. Results showed that the optimal conditions for the flocculation of coal chemical wastewater using P(DAC-MAPTAC-AM) alone are as follows: dosage of 8–12 mg/L, G value of 100–250 s − 1, and pH value of 4–8. The optimal dosage of PAFC is 90–150 mg/L with a pH of 2–12. The optimal dosage for PAFC/P(DAC-MAPTAC-AM) is as follows: PAFC dosage of 90–150 mg/L, P(DAC-MAPTAC-AM) dosage of 8–12 mg/L, and pH range of 2–6. When P(DAC-MAPTAC-AM) was used alone, the optimal removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol were 81.0%, 35.0%, 75.0%, and 80.3%, respectively. PAFC has good tolerance to wastewater pH and good pH buffering. Thus, the flocculation treatment of coal chemical wastewater using the PAFC/P(DAC-MAPTAC-AM) compound also exhibits excellent resistance and buffering capacity.

Study on the culture and degradation characteristics of dominant phenol-degrading bacterium for coal chemical wastewater

To culture dominant phenol-degrading bacterium for bioaugmentation treatment of coal chemical wastewater, 3 phenol-degrading bacterium such as PDB-1, PDB-2 and PDB-3 were enriched and screened from activated sludge in the coal gasification wastewater treatment plant. The culture conditions such as temperature, pH and additional carbon source were analyzed. At last, the degradation effects of raw water were investigated. Results indicated that PDB-2 was the best bacterial strain with the strongest phenol-degrading ability. The degradation rate was 96.6% in 24 h under the initial phenol concentration of 400mg/L. The degradation rates were respectively 89.5% and 96.1% in 24 h and 36h under the initial phenol concentration of 800mg/L. Under the initial phenol concentration of 400mg/L, the dominant phenol-degrading bacterium grew best with the temperature of 30°C and pH of 7∼7.5, and 100mg/L or 200mg/L addition of glucose could further increase the 24 h degradation rate. When the preprocessed coal gasification wastewater was used to acclimate PDB-2, the total phenol and COD concentration of raw water were 18.2 mg/L and 193 mg/L with the corresponding 48h degradation rate of 95.8% and 92.5%.

Catalytic activity and evaluation of Fe-Mn@Bt for ozonizing coal chemical biochemical tail water

The purpose of this study was to improve the ozone utilization rate by preparing a high-efficiency ozone catalyst, and establish an effective model to evaluate catalytic oxidation systems. In this study, Fe-Mn@Bt ozone catalyst prepared by a doping-baking method was used to deeply treat the biochemical tail water of coal chemical wastewater. The catalyst had an extremely developed pore structure characterized by SEM. The catalytically active elements inside and on the catalyst in the form of α-Fe2O3 and MnO2 had good stability. The effects of operating conditions, such as ozone dosage, hydraulic retention time, and catalyst dosage, on total phenol and total organic carbon (TOC) removal rate were systematically investigated. Under optimal working conditions, the chemical oxygen demand (COD) after the degradation of coal chemical biochemical tail water was used as the evaluation index to explore the actual utilization rate of ozone. The addition of Fe-Mn@Bt porous catalyst upgraded the actual utilization rate of ozone from 0.14. kgCOD/kgO3 (ozone alone oxidation system) to 0.22 kg COD/kg O3. The mechanism of catalytic oxidation was investigated by adding a free radical inhibitor to a catalytic oxidation system, demonstrating that the dominant processes in a deep degradation system was that the catalysis of ozone-generated hydroxyl radicals by active elements and ozone oxidation. To further evaluate the operating conditions for Fe-Mn@Bt ozone catalyst, the “3E” evaluation system where economy, energy, and environment were the key factors was established and evaluated. At optimal levels, the removal ratios of total phenol and TOC were 58.7% and 53.5%, respectively. Fe-Mn@Bt ozone catalysts can effectively improve ozone utilization rate and has a good application prospect for the advanced treatment of coal chemical wastewater.

Life cycle economic assessment of coal chemical wastewater treatment facing the ‘Zero liquid discharge’ industrial water policies in China: Discharge or reuse?

Geographical maldistribution of coal and water resource has led to huge water consumption, posing great challenges to the development of coal chemical industries in China. In this study, based on the obtained unit product data of water withdrawal, consumption, and wastewater effluent capacity, the wastewater quantitative information about water quality and relevant energy and reagents consumption for several coal chemical industries were analyzed. Then, the life cycle costs of different types of coal chemical wastewater were analyzed when achieving ICIWD (1st category integrated wastewater discharge) and ZLD (zero liquid discharge) standards. According to the results, the life cycle cost of ICIWD was average 0.94 US$/t water less than that of the wastewater meeting ZLD, because the life cycle boundaries focused on coal chemical industries. Given surface water treatment cost and environment damages value, ICIWD's total cost was 1.07 US$/t water higher than ZLD's. Besides, the consumed water of planning advanced coal chemical projects of 2018 took up 2.8% of total industrial water. Such proportion could even reach over 30% in north and northwest regions. It is suggested that ZLD water policies and water resources appraisal should be introduced to improve and strengthen the rational layout of coal chemical projects.

Reverse osmosis membrane autopsy in coal chemical wastewater treatment: Evidences of spatially heterogeneous fouling and organic-inorganic synergistic effect

Abstract Although fouling on reverse osmosis (RO) membrane has been studied widely, few focused on coal chemical industry where RO is indispensable for water reclamation. The complexity of the wastewater further makes the synergistic mechanism of inorganic and organic foulants unclear. Besides, spatial heterogeneity of fouling at different positions of RO module needs more investigation. This study analyzed samples from a two-stage RO module applied in a full-scale plant for coal chemical wastewater reclamation. Scanning electron microscope equipped with energy dispersive X-ray spectrometer (SEM-EDS), inductively coupled plasma optical emission spectrometer (ICP-OES), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR), confocal laser scanning microscopy (CLSM), three-dimensional excitation-emission matrix (3D-EEM) and 16S sequencing were applied. Results showed that fouling gradually mitigated along the axial direction of the elements. Additionally, from stage-1 to stage-2, although organic fouling constantly dominated, inorganic fouling was aggravated while biofouling was alleviated with declined microbial diversity and population. The structure of microbial community also varied, which was due to the selectivity of higher salinity of the 2nd stage influent and interception of particular species in the 1st stage. Moreover, experimental evidences were provided for the bridging effect of Ca2+ and polysaccharides, as well as the synergistic effect of silicon and organic matters in fouling. The detailed foulant analysis on real membrane samples in this study may lay foundation for improving fouling control strategies in coal chemical industry.

Effect of hydroxypropyl-β-cyclodextrin on the cometabolism of phenol and phenanthrene by a novel Chryseobacterium sp.

Cometabolic degradation is an effective method to remove the polycyclic aromatic hydrocarbons (PAHs) with phenol as growth substrate from coal chemical wastewater (CCW). Unfortunately, the toxicity and low solubility of PAHs always restrict their degradation. In this study, Chryseobacterium sp. H202 was firstly isolated from the aerobic segment of CCW. Then, to improve the cometabolic degradation of PAHs, the effects of hydroxypropyl-β-cyclodextrin (HPCD) were investigated. Phenanthrene removal was accelerated in the presence of phenol; however, the degradation of phenol was inhibited because of the toxicity of phenanthrene. Addition of 50 mg/L HPCD accelerated the degradation of phenol and effectively improved the phenanthrene removal rate by about 55%. Inclusion of HPCD appeared to increase the apparent solubility and reduce the toxicity of phenanthrene, thereby improving the cometabolic degradation of phenol and phenanthrene. Therefore, HPCD can enhance the degradation of phenanthrene with phenol as the growth substrate during CCW treatment.

Adsorption of ammonia nitrogen on lignite and its influence on coal water slurry preparation

Using lignite as an adsorbent and subsequently as a material for coal water slurry (CWS) preparation represents an alternative method for coal chemical wastewater treatment. However, the components in these wastewaters could affect the CWS performance, especially ammonia nitrogen (NH4+-N). The influencing mechanism of NH4+-N was studied through adsorption method. Associated with adsorption reaction model, Fourier transform infrared spectrum and zeta potential detection, it was found that the adsorption reaction of NH4+-N, driven by ion-exchange interactions with H+ of –OH and –COOH on the lignite surface, displayed a typical monolayer mode and was much faster than that of NSF which displayed a double-layer mode and was adsorbed preferentially at hydrophobic sites. In binary adsorption, the adsorption amount of NSF was increased remarkably by adding NH4+-N. This was attributed to the modified lignite surface and hydrophilic group by NH4+-N that decreased the surface electronegativity as well as the electrostatic repulsion among –SO3− in NSF molecules. The enhanced adsorption of NSF resulted in capturing more water molecules in hydration film surrounding the particles in CWS. The hydration film was then thickened and stabilized, thus leading to a decrease in free water for CWS flowing. As a result, the apparent viscosity was increased, and CWS tended to be dilatant. In addition, the thickened and stabilized hydration film also increased the yield stress of CWS prepared with NH4+-N, resulting in improved stability.

Characterizing the roles of organic and inorganic foulants in RO membrane fouling development: The case of coal chemical wastewater treatment

• RO fouling behavior of real coal industrial wastewater was analyzed in detail. • Roles of hydrophobic/philic organics and inorganics (Ca/Mg/Si) were identified. • HON and HIN had the highest fouling potential per unit concentration. • Polysaccharide was responsible for rapid initial fouling and low steady-state flux. • Si further limited the steady-state flux by altering foulant layer structure. In this study, various fouling characteristics on the surface of a commercial reverse osmosis (RO) membrane were identified, in terms of different organic and inorganic components. Specifically, a practical secondary wastewater of coal chemical industry was used as the feed solution, and was fractionated into six hydrophobic/hydrophilic acid/base/neutral portions. RO membrane fouling behaviors at different stages were critically described using two characteristic parameters, i.e., initial flux decline rate and final steady-state flux. These parameters were quantified using Michaelis-Menten relation as a model fitting method. In general, the hydrophilic neutral (HIN) and hydrophobic neutral (HON) fractions had the fastest initial fouling rate and the lowest steady-state flux, mainly due to their high contents of polysaccharide. Among the organic constituents (polysaccharide/protein/humic acid), polysaccharide was the most responsible for rapid initial flux decline and low final steady-state flux, as proved by Kendall’s correlation. Among the inorganic constituents (Ca/Mg/Si), Si was found to exert the greatest influence on the final steady-state flux. This indicates that polysaccharide and Si played a combined role in determining the foulant layer permeability at the prolonged fouling stage, and a possible mechanism is that Si might alter the structure of polysaccharide gel layer. Further information on the fouling layers was systematically provided by means of Fourier transform infrared spectroscopy, confocal laser scanning microscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy with fractal dimension analysis.

Coal Chemical Wastewater Treatment Process Based on Computer Simulation Technology

With a focus on coal chemical wastewater treatment, this study establishes a numerical simulation algorithm based on JAVA language for microwave-assisted coal chemical wastewater treatment, compares the testing results with the numerical simulation results, verifies the validity of the proposed numerical calculation method, and analyzes the effects of different pH values and H2O2 amount on coal chemical wastewater treatment by numerical simulation. In addition, the study analyzes the working principle of microwave-assisted coal chemical wastewater processor under multi-coupling action by calculating the electric field distribution, average power density, temperature field and concentration field in the furnace chamber. When pH = 3 and pH = 4, the removal rate of PNP in wastewater is the highest, reaching above 92.6%. When pH = 3, the reaction rate reaches 0.213/min. When H2O2 amount increases, both the removal efficiency and reaction rate of PNP increase obviously. The highest removal rate of PNP can amount to 93% and the highest reaction rate is 0.211/min. Therefore, the optimal pH value of wastewater treatment is determined to be 3, and the optimal H2O2 amount is 350mg/L.

Development of phenols recovery process with novel solvent methyl propyl ketone for extracting dihydric phenols from coal gasification wastewater

Industrial application shows that dihydric phenols especially hydroquinone is a key problem for coal chemical wastewater treatment. The efficient removal of hydroquinone has high significance for coal chemical industry cleaner production. In this study, the efficient phenols recovery process had been developed. The novel solvent methyl propyl ketone (MPK) was proposed by using the method of structural characteristics integrated computer-aided molecular design (CAMD). The removal efficiencies of MPK with two common solvents diisopropyl ether (DIPE) and methyl isobutyl ketone (MIBK) were compared. The removal efficiency of total phenols can be increased to as high as 99.6% by using MPK, which was better than that using DIPE or MIBK. Moreover, the concentration of total phenols can be reduced from more than 5000 mg/L to less than 100 mg/L. Simulation of phenols recovery process using MPK were conducted to determine the operation parameters. Replacing MIBK with MPK can be applied in industry without any change the size of existing device. The treatment cost estimate showed that the process with solvent MPK had good economic feasibility considering the economic value of crude phenols.

Using combined multiple techniques to characterize refractory organics during anammox process with mature coal chemical wastewater as influent.

This study combined spectroscopy techniques to assess the composition of refractory organics and highlighted the potential application of excitation-emission matrix (EEM) fluorescence spectroscopy within future monitoring of coal chemical wastewater treatment by the anammox process. The results showed that the anammox process could effectively degrade refractory organic substances, with fulvic-like, UV-humic acid, and Vis-humic acid component removal efficiencies of 43.61, 53.93, and 100%, respectively. In this study, EEM fluorescence spectroscopy was proven to be an effective method of assessing the removal of dissolved organic nitrogen during anammox treatment of mature coal chemical wastewater. Furthermore, remarkable accumulation (9.3-16.2%) of Ca. Kuenenia occurred in the anammox granules that underwent long-term cultivation in mature coal chemical wastewater, which provided the high nitrogen removal rate. The abundance of Anaerolineaceae and Bacteroides was vital in refractory organic degradation.

Discussion on Wastewater Treatment Process of Coal Chemical Industry

Coal chemical wastewater has such characteristics as high concentration of oil, ammonia nitrogen and COD. In this paper, treatment process of coal chemical industry is described mainly, such as pretreatment process, biochemical treatment process and polishing process. Through the recovery of phenol and ammonia and the treatment of wastewater from abroad, the new technology of wastewater treatment in coal chemical industry was expounded. Finally, The development of coal chemical wastewater treatment technology is prospected, and the pretreatment technology is emphasized. According to the diversification and utilization of water, zero discharge of coal chemical wastewater will be fulfilled.

Research on the Treatment of Coal Chemical Wastewater by Activated Sludge Process with Fixed Biological Media Process and Strains

Full scale two-stage activated sludge process (ASP) with fixed biological media was used to treat coal gasification wastewater. The ASP has operated for more than one year and COD, total phenol and NH4-N removal effects were illuminated. COD and total phenol removal rates were around 85% and 90% during long term operation. Effluent COD and total phenol of the first stage of the ASP had an abnormal increase and turned to normal after several weeks. Nitrification of the ASP increased slowly and NH4-N removal rates achieved 80% after 15 weeks. Stenotrophomonas maltophilia K279a is isolated from coal chemical industry wastewater. The optimum conditions for PO production are phenol 1000mg/L, temperature 30-34 and pH 7-7.5. The strain resists 980mg/L COD and 805mg/L phenols. The degradation rate of phenols reaches 97% in 48h. The results show that Stenotrophomonas maltophilia K279a can be applied to the aerobic process with high proportion of phenols

Mechanism and Experimental Research on Treatment of Coal Chemical Wastewater by External Circular Anaerobic Reactor

In view of the defects of existing much “dead area” and decreased effective volume causing by distributing water device of UASB reactor, a new-style of external circular(EC) reactor was developed in this research. In this paper, through laboratory scale and pilot scale study on the external circular anaerobic reactor to treat coal chemical wastewater, we conducted profoundly theoretic and testing analysis on external cyclone-flow distribution water device, the results reveal that the new-style anaerobic reactor can largely advance the mixture of granular sludge with wastewater, enhance the availability of reactor’s cubage, heighten mass-transfer efficiency between substrate and microbes, and avoid effectively the losing of granular sludge, further reduce the cost of disposing coal chemical wastewater, which had very important theoretical indication function and practical application value in the development of coal chemical wastewater treatment by anaerobic technology.