Coal Chemical Industry Wastewater Research Articles

Regulatory mechanism of high-concentration CO2 on polysaccharide accumulation in Tetradesmus obliquus cultured in sludge extract

Microalgae such as Tetradesmus obliquus have great potential in immobilizing high-concentration CO2 and removing highly toxic organic matters, which could be produced from coal chemical industry and coal chemical wastewater biological treatment process. In this study, Tetradesmus obliquus was cultured in sludge extract and high-concentration CO2 was added. The maximum cell density and dry weight were respectively (111.46 ± 4.87) × 106 cell/mL and 3.365 ± 0.168g/L under 30% CO2. Tetradesmus obliquus accumulated the most polysaccharides (629.60 ± 31.48mg/L) on the 30th day under 30% CO2. The results of proteomic showed that the upregulation of A0A2Z4THB7 and A0A383VAT1 promoted polysaccharide accumulation. Polysaccharide was mainly formed at the stable phase instead of the log-growth phase due to the abiotic stress caused by high TOC at the log-growth phase. Collectively, this study revealed the regulatory mechanism of high-concentration CO2 on the toxicity removal and accumulation of polysaccharides in Tetradesmus obliquus.

Investigation of the deactivation and regeneration of an Fe2O3/Al2O3•SiO2 catalyst used in catalytic ozonation of coal chemical industry wastewater

Catalyst deactivation is an ongoing concern for industrial application of catalytic ozonation processes. In this study, we systematically investigated the performance of a catalytic ozonation process employing Fe2O3/Al2O3•SiO2 catalyst for the treatment of coal chemical industry (CCI) wastewater using pilot-scale and laboratory-scale systems. Our results show that the activity of the Fe2O3/Al2O3•SiO2 catalyst for organic contaminant removal deteriorated over time due to formation of a dense and thin carbonaceous layer on the Fe2O3 catalyst surface. EPR and fluorescence imaging analysis confirm that the passivation layer essentially inhibited the O3-catalyst interaction thereby minimizing formation of surficial •OH and associated oxidation of organic contaminants on the catalyst surface. Calcination was demonstrated to be effective in restoring the activity of the catalyst since the carbonaceous layer could be efficiently combusted during calcination to re-establish the surficial •OH-mediated oxidation process. The combustion of the carbonaceous layer and restoration of the Fe layer on the surface on calcination was confirmed based on SEM-EDX, FTIR and thermogravimetric analysis. Cost analysis indicates that regeneration using calcination is economically viable compared to catalyst replacement. The results of this study are expected to pave the way for developing appropriate regeneration techniques for deactivated catalysts and optimising the catalyst synthesis procedure.

Hybrid peroxi-coagulation/ozonation process for highly efficient removal of organic contaminants

Aromatic compounds such as phenols presented widely in coal chemical industry wastewater (CCW) render the treatment facing great challenge due to their biorefractory characteristics and potential risks to the environment and human health. Ozone-based advanced oxidation processes show promising for these pollutants removal, but the mineralization via ozonation alone is unsatisfactory and not cost-effective. Herein, a hybrid peroxi-coagulation/ozonation process (denoted as PCO) was developed using sacrificial iron plate as an anode and carbon black modified carbon felt as cathode in the presence of ozonation. An enhanced phenol removal of ∼100% within 20 min and phenol mineralization of ∼80% within 60 min were achieved with a low energy consumption of 0.35 kWh/g TOC. In this novel process, synergistic effect between ozonation and peroxi-coagulation was observed, and beside O3 direct oxidation, peroxone played a dominant role for phenol removal. In the PCO process, the hydrolyzed Fe species enhanced the generation of reactive oxygen species (ROS), while •OH was dominantly responsible for pollutant degradation. This process also illustrated high resistance to high ionic strength and better performance for TOC removal in real wastewater when compared with ozonation and peroxi-coagulation process. Therefore, this process is more cost-effective, being very promising for CCW treatment.

An optimized design for zero liquid discharge from coal chemical industry: A case study in China

Zero liquid discharge (ZLD) is an efficient solution for the issue of global water scarcity. To improve energy efficiency, existing units should be optimized treat coal chemical industry (CCI) wastewater. This study introduced a new design and optimization model for a CCI wastewater treatment approach that may achieve ZLD, as well as minimizing wastewater treatment costs. The model, considered treatment chemicals, flowrate, salinity, and operating pressure. Using different input conditions, the use of the ZLD system for CCI wastewater treatment was illustrated, and the respective mass balance diagram was developed. In addition, the economic cost of different units for each scenario involved in treating CCI wastewater was calculated. The levelized cost of water (LCOW) reached 1.325 $/m3 when the salinity of input is 3000 mg/L. Furthermore, an environmental impact analysis was conducted on chemical, electricity, steam and solid waste for each technology in the ZLD system for treating CCI wastewater. This study presents an effective design and optimization process that could significantly screen CCI wastewater for the application of a ZLD process with the goal of reducing environmental impacts and minimizing the cost of wastewater treatment.

A full-scale study of nanofiltration: Separation and recovery of NaCl and Na2SO4 from coal chemical industry wastewater

This study focuses on the application of nanofiltration membrane in separating NaCl from Na2SO4 of a “zero discharge” process designed for a particular coal chemical wastewater (60 m3/h) in full scale. The front-end inlet water's residual chlorine content seriously affects the subsequent nanofiltration membrane's long-term efficiency. The nanofiltration membrane was oxidized when the front-end inlet residual chlorine exceeds 0.1 mg/L. In 1-year operation, the rejection rate of the nanofiltration membrane for chemical oxygen demand (COD) dropped from ~70% to ~50%, and the rejection rate for silica dropped from ~30% to ~20%; in the same period, the rejection rate for sodium sulfate dropped from 99.5% to ~88%. It was found that coconut shell activated carbon, a pre-treatment unit integrated in front of the nanofiltration membrane unit, could remove up to 98% of residual chlorine in the system. The chlorine concentration entering the nanofiltration unit was kept below 0.05 mg/L, thus maintaining the nanofiltration membrane's efficiency and extending its lifespan. This work provides a foundation for the nanofiltration in separation and resource of NaCl and Na2SO4 from a large-scale perspective and implication for the development of Nanofiltration membrane for coal chemical wastewaters.

Treatment of wastewater containing 2-methoxyphenol by persulfate with thermal and alkali synergistic activation: Kinetics and mechanism

Both thermal and alkali are effective means of persulfate (PS) activation, and the synergistic effect of them should achieve a great degradation result. It is evaluated for treating coal chemistry industry wastewater because the by-product produced in the process is sulfate, which is pre-existing in the wastewater. With thermal and alkali synergistic activation, the application of the response surface method revealed the effects of temperature, pH and concentration of persulfate on the degradation ratio of 2-methoxyphenol (MOP, a typical contaminant in coal chemical industry wastewater) and their interactions. The results showed that the degradation rate of the contaminant was temperature and pH dependent, while chloride (Cl−) and sulfate (SO42−) ions had no obvious negative effect. The degradation ratio could be enhanced with higher activation temperature and pH (7–12). The faster degradation could be achieved by thermal-alkali synergistic activation, and the degradation ratio of 88.4% and 93.8% could be achieved at pH = 12 within 10 min and 20 min, respectively. Electron spin resonance (ESR) spectra and free radical scavenging experiments indicated that MOP degradation was achieved by the oxidation of both sulfate radical (SO4−) and hydroxyl radical (OH) at pH = 6, and only by OH at pH = 12. In addition, the radical reaction was intense under thermal-alkali synergistic activation of PS, while the quenching reaction was ineffective.

Phase equilibrium measurement, thermodynamics modeling and process simulation for extraction of phenols from coal chemical wastewater with methyl propyl ketone

The extraction of phenols from coal chemical industry wastewater with methyl propyl ketone was studied in this work by experimental determination and process simulation. Phenol and hydroquinone were separately selected as the representatives of phenolic pollutants in the phenols-containing coal chemical industry wastewater. The liquid–liquid phase equilibrium data for methyl propyl ketone+phenol+hydroquinone+water quaternary system were measured at 40°C and 101.3kPa. The NRTL and UNIQUAC models were used to correlate the experimental data to achieve binary interaction parameters. The process simulation for the extraction of phenols from coal chemical industry wastewater with methyl propyl ketone was developed to obtain optimized operation parameters with the binary interaction parameters fitted from the experiment. The simulation results show that, the concentration of total phenols in the coal chemical industry wastewater could be reduced from 12,700mgL−1 to 313mgL−1 in the stream of the bottom in the stripping column, which is suitable for further biochemical treatment of the wastewater. The extraction solvent could be recycled through the distillation column and the stripping column. The crude phenols would be as by product in the phenols extraction and solvent recovery.

Preparation and properties of Cu-Ni bimetallic oxide catalyst supported on activated carbon for microwave assisted catalytic wet hydrogen peroxide oxidation for biologically pretreated coal chemical industry wastewater treatment

A microwave (MW)-assisted catalytic wet hydrogen peroxide oxidation (CWHPO) process was investigated to treat biologically pretreated coal chemical industry wastewater (CCIW) in this study. The activated carbon (AC) supported Cu-Ni bimetallic oxide catalyst was prepared by impregnation and precipitation method for MWCWHPO. The catalytic performance of the catalyst was investigated, and the main influencing factors were discussed. The results showed that the removal efficiencies of quinoline and total organic carbon (TOC) with catalyst prepared by impregnation method were 85% and 70%, respectively, and the removal efficiencies of quinoline and TOC with catalyst prepared by precipitation method were up to 95% and 76%, respectively. The utilization rate of hydrogen peroxide (H2O2) and the generation quantity of hydroxyl radicals were higher in the reaction process with the catalyst prepared by precipitation method than those with the catalyst prepared by impregnation method. The characterization of the catalyst showed that the smaller active component grains size, larger surface area and higher proportion of chemical adsorption oxygen were the main reason for the high catalytic efficiency. Furthermore, the optimized reaction conditions were: reaction temperature of 60 °C, microwave power of 500 W, and H2O2 initial concentration of 0.066 M. Moreover, the Cu-Ni bimetallic oxide catalyst is an efficient and stable catalyst in the degradation and mineralization of pollutants in the MWCWHPO process. The synthesized catalyst was verified to be attractive for use in the heterogeneous wet peroxide oxidation system under microwave irradiation.

Enhanced performance and hindered membrane fouling for the treatment of coal chemical industry wastewater using a novel membrane electro-bioreactor with intermittent direct current

A membrane electro-bioreactor (MEBR) embracing biological treatment, electrokinetic phenomena and membrane filtration was established by applying intermittent direct current (DC) to MBR. MEBR exhibited significant improvement of treatment performance and reduction of membrane fouling. COD and total phenols removal efficiencies increased to 83.53% and 93.28% at an exposure mode of 24′-OFF/6′-ON, compared to 71.24% and 82.43% in MBR. Trans-membrane pressure increment rate declined dramatically in MEBR, which was mainly attributed to the increase of sludge floc size and decrease of zeta potential, soluble microbial products and specific resistance to filtration, resulted from electrokinetic effects such as electrocoagulation, electrophoresis, electroosmosis and electromigration of ions. It was notable that DC exposure exerted distinct evolution on microbial community, with the improvement of microbial community richness and diversity. The relative abundances of functional genera were promoted noticeably in MEBR. An interactive relevance existed among microbial community structure, mixed liquor properties and operational parameters.

Experimental result and data correlation of liquid-liquid equilibrium for methyl isopropyl ketone + o, m, p-dihydroxybenzene + water at 333.15 K, 343.15 K and 353.15 K

In order to remove the dihydroxybenzene from coal chemical industry wastewater at high temperatures, the liquid-liquid equilibrium data of ternary system methyl isopropyl ketone (MIPK) + o, m, p-dihydroxybenzene + water was measured at 333.15 K, 343.15 K and 353.15 K under 101.3 kPa. The extraction effect of MIPK on dihydroxybenzene was evaluated by the distribution coefficient (D) and the separation factor (S). The Hand equation and the Bachman equation were used for verifying the consistency of the experimental data. Both regression coefficients were higher than 0.99, and it indicated that the experimental data had excellent reliability. Meanwhile, NRTL and UNIQUAC models were applied to correlate experimental liquid-liquid equilibrium data and then the binary interaction parameters were obtained. RMSD values of both models were similar and did not exceed 0.0050. Finally, comparing the extraction effect of MIPK between high and low temperatures, it was found that MIPK also can effectively extract the dihydroxybenzene from wastewater at high temperatures.

Advanced treatment of biologically pretreated coal chemical industry wastewater using the catalytic ozonation process combined with a gas-liquid-solid internal circulating fluidized bed reactor.

This paper investigated the performance of the combined system of catalytic ozonation and the gas-liquid-solid internal circulating fluidized bed reactor for the advanced treatment of biologically pretreated coal chemical industry wastewater (CCIW). The results indicated that with ozonation alone for 60min, the removal efficiency of chemical oxygen demand (COD) could reach 34%. The introduction of activated carbon, pumice, γ-Al2O3 carriers improved the removal performance of COD, and the removal efficiency was increased by 8.6%, 4.2%, 2%, respectively. Supported with Mn, the catalytic performance of activated carbon and γ-Al2O3 were improved significantly with COD removal efficiencies of 46.5% and 41.3%, respectively; however, the promotion effect of pumice supported with Mn was insignificant. Activated carbon supported with Mn had the best catalytic performance. The catalytic ozonation combined system of MnOX/activated carbon could keep ozone concentration at a lower level in the liquid phase, and promote the transfer of ozone from the gas phase to the liquid phase to improve ozonation efficiency.

Application of Resin in Advanced Treatment of Coal Chemical Industry Wastewater

The adsorptive qualities of NDA-150 resin on coal chemical wastewater were studied under different conditions by static adsorption test. The results showed that NDA-150 resin played a good adsorptive effect on coal chemical wastewater. After treatment, the removal rate of chemical oxygen demand (COD) was more than 82%. The used resin could be regenerated and the removal rate of COD reached up to 75%, which effectively realized the advanced treatment of coal chemical industry wastewater.

Advanced Treatment of Coal Chemical Industry Wastewater by Electro-Catalysis with Gd-Doped Ti/SnO2 Anode

Advanced Treatment of Coal Chemical Industry Wastewater by Electro-Catalysis with Gd-Doped Ti/SnO2 Anode

Effect of alkalinity on nitrite accumulation in treatment of coal chemical industry wastewater using moving bed biofilm reactor

Nitrogen removal via nitrite (the nitrite pathway) is more suitable for carbon-limited industrial wastewater. Partial nitrification to nitrite is the primary step to achieve nitrogen removal via nitrite. The effect of alkalinity on nitrite accumulation in a continuous process was investigated by progressively increasing the alkalinity dosage ratio (amount of alkalinity to ammonia ratio, mol/mol). There is a close relationship among alkalinity, pH and the state of matter present in aqueous solution. When alkalinity was insufficient (compared to the theoretical alkalinity amount), ammonia removal efficiency increased first and then decreased at each alkalinity dosage ratio, with an abrupt removal efficiency peak. Generally, ammonia removal efficiency rose with increasing alkalinity dosage ratio. Ammonia removal efficiency reached to 88% from 23% when alkalinity addition was sufficient. Nitrite accumulation could be achieved by inhibiting nitrite oxidizing bacteria (NOB) by free ammonia (FA) in the early period and free nitrous acid in the later period of nitrification when alkalinity was not adequate. Only FA worked to inhibit the activity of NOB when alkalinity addition was sufficient.

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

The laccase conditons of efficient hydroxybenzene-degrading bacteria in Coal Chemical Industry Wastewater

The laccase conditons of efficient hydroxybenzene-degrading bacteria in Coal Chemical Industry Wastewater