Coal Wastewater Research Articles

Comparing the effectiveness of chitosan and conventional coagulants for coal wastewater treatment

In this research, the potential of chitosan to be used as a coagulant to treat coal wastewater was investigated, in comparison to a conventional coagulant, i.e: Al2(SO4)3 or aluminum sulfate, and Poly Aluminium Chloride (PAC). The parameters being studied were turbidity, pH, TDS, and TSS. The result of this research showed that chitosan worked as a more efficient coagulant to treat coal wastewater compared to alum and PAC, in terms of the needed dose of application. The optimum dose of chitosan was 20 mg/L that gave a 100% decrease in turbidity and TSS. On the other hand, a dose of 120 mg/L of alum was needed to have an optimum result, where the turbidity and TSS were decreased up to 100%. When PAC was used as a coagulant, the optimum dose was 120 ppm that reduced turbidity and TSS to 99.50% and 99.58%, respectively. Coagulation by chitosan, alum, and PAC were all influenced by pH, where the optimum pH for all three coagulants was within a range of neutral pH.

Characterisation of floc size, effective density and sedimentation under various flocculation mechanisms.

Floc structure plays an important role in the separation of coal wastewater. In this study, a camera-based method is used to evaluate quantitatively the structural characteristics of flocs generated by different coagulants and flocculants. The correlations between particle size, settlement velocity and effective density of coal tailings flocs are analysed. The results show that the statistical settling velocity increases linearly with floc size, while the effective density decreases with increase in floc size. Different flocculation mechanisms lead to diverse growth abilities of flocs. When the flocculant is used alone, the quality of the flocs generated by the flocculants, cationic polyacrylamide (CPAM) and non-ionic polyacrylamide (NPAM), is better than that generated by anionic polyacrylamide (APAM). However, the combination of trivalent cations and APAM yields a much better effect than that obtained using CPAM and NPAM. Flocs become larger and more compact when treated with a coagulant combined with a flocculant.

Economic Analysis of Syngas Production by Coupling Coal Gasification Wastewater Treatment and Solid Oxide Cell System

Coal is the main energy source in China, and coal chemistry wastewater treatment has always been a research hotspot. For the large amount of concentrated organic wastewater, high cost caused by complex treatment process is the key issue. In this paper, the fixed bed Lurgi gasifier wastewater coupled with solid oxide cells (SOCs) system is employed for its treatment. Based on Aspen Plus software, the purified methane from marsh gas is sent to solid oxide fuel cell (SOFC) for electricity generation. While carbon dioxide separated from biogas purification and acid gas removal enters solid oxide electrolysis cell (SOEC) to produce syngas by co-electrolysis with steam.The simulation results show that the efficiency of SOFC is 48.5 %. The generated electric energy can be used for auxiliary equipment in wastewater treatment and SOEC to produce syngas, recycling of carbon dioxide. SOEC with wind power of 12.84 MW is enough to treat the waste gas generated by the 1,100 t/h Lurgi gasification wastewater treatment process. Economically, the cost of producing syngas, with high purity and fewer contaminant contents, is about 0.126 $/Nm3. It can be used to produce various chemicals, so as to further improve the economic benefit of wastewater treatment.

Study on coal water slurries prepared from coal chemical wastewater and their industrial application

The coal water slurry gasification combined with ammonia synthesis process produces various complex wastewaters that are difficult to handle, and the improper disposal of these wastewaters causes great harm to the environment. In this paper, coal wastewater slurry was prepared from these wastewaters, and its slurryability, rheology and stability were measured. The gasification characteristics were studied in a coal water slurry gasifier. Results show that (a) The gas washing wastewater, sulfur wastewater and industrial wastewater can promote slurryability, whereas carbonized water is not conducive to promoting slurryability. The mixed wastewater, that comprises all four types of wastewater mentioned above, promotes slurryability and has a slurry concentration of 62.0%. All coal wastewater slurries exhibit pseudoplastic fluid property, which are beneficial for industrial pumping and atomization. The stability of the samples was evaluated by analyzing the water separation rate, and all coal wastewater slurries show better stability than the coal deionized water slurry. (b) In the industrial application process, the active component of the syngas produced from the gasification of the coal mixed wastewater slurry can reach 78.6% and has a higher H2 content than the syngas produced from ordinary coal water slurry. Moreover, using the coal mixed wastewater slurry can increase cold gas efficiency by 1.57% and carbon conversion rate by 0.45% in industrial processes. Therefore, preparing and using coal mixed wastewater slurry in coal water slurry gasification combined with ammonia synthesis process not only treats high-concentration wastewater but also achieves sustainable development and a circular economy model.

Regional Comparison of Impacts to Stream Macroinvertebrates from Active and Inactive Coal Mine Wastewater Discharges, Sydney Basin, New South Wales Australia

This study investigates macroinvertebrates from waterways receiving wastewater from coal mines in the Sydney Basin. Three of the coal mines were inactively mining oar and four actively mining oar during sampling. Macroinvertebrates were collected from each collieries receiving waterway upstream and downstream of all mine wastewater inflows. All the coal mines wastewater discharges are licensed and regulated by the New South Wales Environment Protection Authority (NSW EPA). Results of the study show that the coal mine wastewaters being discharged are having varying negative impacts to the receiving waterways aquatic ecosystem through macroinvertebrate biotic indices, despite whether mining is active or inactive. Biotic indices measured at active and inactive coal mines show that actively mined wastewaters are most likely causing less of an impact to the receiving waterways aquatic ecosystem than inactively mined wastewaters. All the waterways receiving un-treated (inactively mining) wastewaters recorded statistical differences for all biotic indices when analysed between their upstream and downstream sample locations. This was in contrasted to the actively mined (treated wastewaters) with only one of the streams sampled recording statistical differences for all biotic indices. Results suggest that once mining ceases and the treatment of the coal mine wastewaters subsequently ceases the receiving waterways aquatic ecosystem are clearly more degraded. This is of great concern as once mining ceases so does the treatment of their wastewaters. It is recommended that the NSW EPA further investigate measures of treatment post coal mining at these mines to ensure further degradation of the receiving waterways ecosystem does not occur.

Application of Membran Polyvinylidenefluoride (PVDF) Synthesis Blending TiO<sub>2</sub>-Serbuk Kelor (Moringa Oleifera) Seed on Coal Wastewater Treatment

Membrane technology is the right choice with its ability as a highly selective separation process to produce high quality products. The technology research applied based on chemical technology of Advanced Oxidation Process (AOP), a technology of coal wastewater treatment using strong oxidizing agents with photocatalysts TiO₂ and moringa seed powder (Moringa oleifera). The research methodology used was preparation of Moringa seeds, synthesis of composite photocatalyst TiO₂-Moringa seed powder and manufacture of membrane Polyinylideneflouride (PVDF)-Moringa seed powder with a total of 4 membranes (A, B, C, D). The results of the study produced membrane characteristics with a pore size of 0,1 μm - 6 μm, wet weight of 20% and an average tensile test value of 4.53 N/mm2. Application of membrane PVDF-synthesis TiO₂-Moringa seed powder (Moringa oleifera) in coal wastewater treatment resulted in a decrease of 89% in Fe and Mn pollutants in the composition of 5% TiO₂ and 5% Moringa seed powder in Membrane B.

Increased biodegradability of low-grade coal wastewater in anaerobic membrane bioreactor by adding yeast wastes

Demineralization is required in upgrading low-grade coal to serve as an alternative energy resource for the production of fuel and valuable chemicals but generates a large amount of low-grade coal wastewater (LCWW). The objective of this study was to investigate the effects of a co-substrate on an anaerobic membrane bioreactor (AnMBR) treating LCWW. CH4 was not produced during the operation fed by LCWW alone. When yeast wastes (YW) were supplemented, there was a gradual increase in the biodegradability of LCWW, achieving 182 CH4 mL/g COD with 58% COD removal efficiency. The analysis of physicochemical characteristics in the effluent of AnMBR, done by excitation-emission matrix (EEM) and size exclusion chromatography (SEC), showed that the proportion of soluble microbial products (SMPs) and aromatic group with high-molecular weight (>1 kDa) increased. Microbial analysis revealed that the increased dominance of bacteria Comamonas, Methanococcus, and Methanosarcina facilitated biodegradation of LCWW in the presence of YW.

The synthetic activities of TiO2-moringa oleifera seed powder in the treatment of the wastewater of the coal mining industry

To process the coal wastewater, the combination of chemical based technology of Advanced Oxidation Process (AOP) of a strong oxidizer using TiO2 photocatalyst and biological treatment of moringa seed powder (Moringa oleifera) is used in the composite form. AOP can be used as an alternative treatment of coal wastewater which is quite economical and environmentally friendly. The XRD results of TiO2 powder and the synthesis of TiO2 - is moringa seed powder in the form of tetragonal crystals. The degradation results of the quality of the coal wastewater using TiO2 powder reached a decrease of (TSS, Fe, Mn, Zn, Hg, Cu, Co, Cr, Al and Ni) by an average of 70% and the increase of pH value of 7 at 200 minute stirring time. The decrease of the wastewater quality using the synthesis of TiO2- moringa seed powder by using sunlight and without sunlight is detected negative (-) at 200 minute stirring time.

Study on bubble column humidification and dehumidification system for coal mine wastewater treatment.

Water is important resource for human survival and development. Coal mine wastewater (CMW) is a byproduct of the process of coal mining, which is about 7.0 × 1010 m3 in China in 2016. Considering coal mine wastewater includes different ingredients, a new bubble column humidification and dehumidification system is proposed for CMW treatment. The system is mainly composed of a bubble column humidification and dehumidification unit, solar collector, fan and water tank, in which air is used as a circulating medium. The system can avoid water treatment component blocking for reverse osmosis (RO) and multi effect distillation (MED) dealing with CMW, and produce water greenly. By analysis of heat and mass transfer, the effects of solar radiation, air bubble velocity and mine water temperature on water treatment production characteristics are studied. Compared with other methods, thermal energy consumption (TEC) of bubble column humidification and dehumidification (BCHD) is moderate, which is about 700 kJ/kg (powered by solar energy). The results would provide a new method for CMW treatment and insights into the efficient coal wastewater treatment, besides, it helps to identify the parameters for the technology development in mine water treatment.

Application of Electrocoagulation Process for Continuous Coal Stockpile Wastewater Treatment System

Coal wastewater is characterized by high total suspended solid (TSS), heavy metals, and low acidity (pH). The purpose of this study was to research the effects of the operating parameters such as applied voltage, the number of electrodes, and reaction time on a real coal stockpile wastewater in the continuous electrocoagulation process. For this purpose, aluminum electrodes were used in the presence of potassium chloride as an electrolyte. It has been shown that the removal efficiency of TSS and heavy metals content increased with increasing the applied voltage and reaction time. The results indicate that the electrocoagulation process is efficient and able to achieve 88.67% TSS removal, 95.65% ferrous removal, 99.11% manganesse removal, and pH increased until 7.1 at 24 volts during 120 min, respectively. The experiments demonstrated the effectiveness of electrocoagulation methods for the treatment of coal stockpile wastewater. Key words : coal stockpile wastewater, electrocoagulation, electrode

Nano zero valent iron/modified semicoke composites for the removal of coal tar wastewater

ABSTRACTThe coal tar wastewater was treated by self-synthesized nano zero valent iron (NZVI)/modified semicoke composites. Phenol was employed as simulated sample due to high content of phenol in coal tar wastewater. The results show that the phenol removal rate started to rise with the increase of modified semicoke amount and aging time, reached maximum at certain value, and then began to decrease. With the reaction time extending, phenol removal rate increased gradually, while phenol removal rate came down gradually as the initial phenol concentration rise. The XPS, XRD, and SEM results indicate that NZVI with uniform size was well-distributed on the surface of modified semicoke.

Hydrochemistry and coal mining activity induced karst water quality degradation in the Niangziguan karst water system, China.

Hydrogeochemical analysis, statistical analysis, and geochemical modeling were employed to evaluate the impacts of coal mining activities on karst water chemistry in Niangziguan spring catchment, one of the largest karst springs in Northern China. Significant water quality deterioration was observed along the flow path, evidenced from the increasing sulfate, nitrate, and TDS content in karst water. Karst water samples are Ca-Mg-HCO3 type in the recharge areas, Ca-Mg-HCO3-SO4 type in the coal mining areas, and Ca-Mg-SO4-HCO3/HCO3-SO4 type in the rural areas and discharge areas. A four-factor principal component analysis (PCA) model is conducted which explains over 82.9% of the total variation. Factor 1, which explained the largest portion (45.33%) of the total variance, reveals that coal mining activities and natural water-rock interaction as the primary factors controlling karst water quality. Anthropogenic effects were recognized as the secondary factor with high positive loadings for NO3 (-) and Cl(-) in the model. The other two factors are co-precipitation removal of trace elements and silicate mineral dissolution, which explained 20.96% of the total variance. A two-end mixing modeling was proposed to estimate the percentage of coal wastewater giving on karst water chemistry, based on the groundwater sulfate chemistry constrains rather than sulfur isotopes. Uncertainty of sulfur isotope sources led to an overestimation of coal mining water contribution. According to the results of the modeling, the contribution of coal mining waste on karst water chemistry was quantified to be from 27.05 to 1.11% which is ca. three times lower than the values suggested using a sulfur isotope method.

Preparation of Amphoteric Polyacrylamide-Grafted Starch Flocculant and its Application

A polyacrylamide-grafted starch (St-g-AM-DMC-AMPS) flocculant for the coal slurry wastewater was prepared by using corn starch (St), acrylamide (AM), methyl acryloyloxyethy trimethyl ammonium chloride (DMC) as cationic monomer, 2-acrylamido-2-methyl acrylate sulfonic acid (AMPS) as anionic monomer through solution polymerization. The structure of the synthesized St-g-AM-DMC-AMPS was characterized by FT-IR and TG. The effects of initiator concentration, reaction temperature and monomer concentration on percentage of grafting and the grafting efficiency were investigated. The results showed that the optimal conditions of the polymerization are that the ratio of substrate and monomer is 3:7, the radio of ammonium persulfate is 0.15%, reaction time is 4h and reaction temperature is 50°C. The additional dosage of St-g-AM-DMC-AMPS is varying between 12mg/L and 20 mg/L to obtain better flocculation capability than PAM.

Effect of Media Packing Density on the Performance of Anaerobic Hybrid Reactors for the Treatment of Complex Phenolic Wastewater

AbstractThe effect of media packing on the performance of anaerobic hybrid reactors (combining upflow anaerobic sludge blanket reactors and anaerobic filters) was examined for the treatment of simulated coal wastewater at four hydraulic retention times (HRTs) under mesophilic (27±5°C) conditions. PVC rings were used as filter media; they were maintained at varying packing densities in three experimental reactors (R1, R2, and R3) at 34.29, 24.29, and 14.13 kg m−3. Synthetic coal wastewater with an average chemical oxygen demand of 2,240 mg L−1 and concentration of phenolics of 752 mg L−1 was used as substrate. During the four-month operation, the HRT was shortened from 0.66 to 0.33 days. The removal of phenolics was favored in Reactors R1 (98−92%) and R2 (96–86%) more than R3 (94−82%) with the reduction of HRT. Biomass concentration of Reactors R1 and R2 increased from 42 to 69.7 and 64.7 g VSS L−1 with an increase in the density of the packing media. Microbial biomass distribution revealed the lowest ...

Evaluation of environmental effect of coal stockpile in Muara Telang, Banyuasin, Indonesia

Stockpile commonly serves as a temporary dump before the coal is transported through the waterways. This study investigated the effects of coal stockpiles on the surrounding environment: air, water, and soil. The location of the study is in the estuary of Telang, South-Sumatra, Indonesia, which is located at the edge of the river of Telang and close to the residential community. The monitoring of the environmental impact from the stockpile is intended to conduct an environmental assessment owing the existence and operations of coal accumulation. Enviromental impact analysis was conducted based on the value of the effluent, air pollution (dust), soil and water by determining the parameters of the coal wastewater pH, total suspended solid, ferrous dan ferrous metals contents. The results indicate that the total suspended particulate, total suspended solids, noise level, ferrous metal and manganese metal were 10-14 μg/Nm3 249-355 mg/L, 41.3 to 50.3 dBA, 6.074 to7.579 mg/L, and 1.987 to 2.678 mg/L, respectively. Meanwhile the pH of water and soil were 3 to 4 and 2.83 to 4.02 respectively. It is concluded that the pH value are beyond the threshold standard.

Performance of anaerobic hybrid reactors for the treatment of complex phenolic wastewaters with biogas recirculation

This study investigates the application of a novel anaerobic hybrid reactor (AHR) configuration, incorporating support media for biomass immobilisation and biogas recirculation for improved mixing towards the anaerobic treatment of complex phenolic wastewater. Synthetic coal wastewater with an average phenolics and COD concentration of 752 and 2240mgL−1 was used as substrate. Biogas recirculation was employed at four different rates of 11.25, 16.87, 25.30 and 37.95Ld−1 for 100days. Phenolics and COD removal improved with increase in biogas recirculation. After 120days of continuous operation, the results revealed that a high amount (14.0g VSS) of biomass was able to attach itself to the support medium. The investigated AHR configuration achieved phenolics and COD removal efficiencies of 95% and 92% respectively at a hydraulic retention time (HRT) of 0.33d. The corresponding average methane production obtained in this study was 0.02mol methaneg−1 COD.

Performance and energy economics of mesophilic and thermophilic digestion in anaerobic hybrid reactor treating coal wastewater

Two anaerobic hybrid AHRs (AHR), mesophilic (35°C) and thermophilic (55°C) were operated with coal wastewater at different hydraulic retention times (HRT) ranging from 3–0.5 to 3.12–0.6d with organic loading rates (OLR) of 1.12–6.72gL−1d−1. Synthetic coal wastewater with an average chemical oxygen demand (COD) of 2240mgL−1 and phenolics concentration of 752mgL−1 was used as substrate. At each HRT, the thermophilic AHR gave a better performance, measured in terms of phenolics/COD removal and gas production. The specific methane yield was also higher for thermophilic AHR at each HRT compared to mesophilic one. The volatile fatty acid concentration in the effluent increased with the lowering of HRT. The Stover–Kincannon model was applicable at both temperatures and showed higher substrate utilization in thermophilic AHR. Energy economic study of the AHRs revealed that 11,938MJd−1 more energy can be generated using thermophilic AHR than mesophilic.

Preparation of Cationic Polyacrylamide Flocculant and its Application in the Treatment of Coal Slurry Wastewater

A cationic polyacrylamide flocculant (CPAM) for the coal slurry wastewater, was firstly synthesized using acrylamide and cationic monomer ethylene methyl propenoyl trimethylammonium chloride (DMC). The structure of the synthesized CPAM was characterized by means of FT-IR measurement, and the effects of various factors on flocculation performance were studied. The optimum flocculation can be achieved according to the dosage of flocculant between 2 and 5 mg/L, pH value of 6, temperature of 40°C, and the dosage of DMC in CPAM of 17.5%.

Comparative performance of UASB and anaerobic hybrid reactors for the treatment of complex phenolic wastewater

The performance of an upflow anaerobic sludge blanket (UASB) reactor and an anaerobic hybrid reactor (AHR) was investigated for the treatment of simulated coal wastewater containing toxic phenolics at different hydraulic retention times (0.75–0.33d). Fast start-up and granulation of biomass could be achieved in an AHR (45d) than UASB (58d) reactor. Reduction of HRT from 1.5 to 0.33d resulted in a decline in phenolics removal efficiency from 99% to 77% in AHR and 95% to 68% in UASB reactor respectively. AHR could withstand 2.5 times the selected phenolics loading compared to UASB reactor that could not withstand even 1.2 times the selected phenolics loading. Residence time distribution (RTD) study revealed a plug flow regime in the AHR and completely mixed regime in UASB reactor respectively. Energy economics of the reactors revealed that 12,159MJd−1 more energy can be generated using AHR than UASB reactor.

Preparation of Cationic Polyacrylamide-Grafted Starch Flocculant and its Application in the Treatment of Coal Slurry Wastewater

A cationic polyacrylamide-grafted starch (St-g-CPAM) flocculant for the coal slurry wastewater, was prepared by using corn starch and acrylamide (AM) as monomers, ethylene methyl propenoyl trimethylammonium chloride (DMC) as cationic monomer through solution polymerization. The effects of initiator concentration, reaction temperature, and monomer concentration on percentage of grafting and the grafting efficiency were investigated. The results show that the optimal conditions of the polymerization are as follows: the monomer to substrate ratio of 2.5, AM:DMC ratio of 2:1, potassium persulfate of 3×10-3 mol/L, reaction time of 4h, the reaction temperature of 50°C. The additional dosage of St-g-CPAM is varying between 20 and 30 mg/L to obtain good flocculation capability