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Our paper presents the possibility of phenol removal from post-processing wastewater originating from an experimental simulation of the underground coal gasification process carried out in the Barbara Experimental Mine in Mikołów, Poland. The application of initial coagulation-flocculation processes with iron(II), iron(III), aluminum, titanium(IV),...
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... The extensive effort has been devoted to developing various cost-effective and environmentally friendly processes to removal of hazardous and refractory organic compunds from the wastewater. So far, integrated engineering systems including biological and chemical advanced treatment system as holistic approach have been considered to clean up of UCG wastewater [2,[8][9][10]. The development of an appropriate treatment method to remove pollutants from UCG wastewater is extremly important for the successful application of UCG technology in energy transformation. ...
The wastewater from underground coal gasification (UCG) process has extremely complex composition and high concentrations of toxic and refractory compounds including phenolics, aliphatic and aromatic hydrocarbons, ammonia, cyanides, hazardous metals and metalloids. So, the development of biological processes for treating UCG wastewater poses a serious challenge in the sustainable coal industry. The aim of the study was to develop an innovative and efficient wetland construction technology suitable for a treatment of UCG wastewater using available and low-cost media. During the bioremediation process the toxicity of the raw wastewater decreased significantly between 74%—99%. The toxicity units (TU) ranged from values corresponding to very high acute toxic for raw wastewater to non-toxic for effluents from wetland columns after 60 days of the experiment. The toxicity results correlated with the decrease of some organic and inorganic compounds such as phenols, aromatic hydrocarbons, cyanides, metals and ammonia observed during the bioremediation process. The removal percentage of organic compounds like BTEX, PAHs and phenol was around 99% just after 14 days of treatment. A similar removal rate was indicated for cyanide and metals (Zn, Cr, Cd and Pb). Concluded, in order to effectively assess remediation technologies, it is desirable to consider combination of physicochemical parameters with ecotoxicity measurements. The present findings show that wetland remediation technology can be used to clean-up the heavily contaminated waters from the UCG process. Wetland technology as a nature-based solution has the potential to turn coal gasification wastewater into usable recycled water. It is economically and environmentally alternative treatment method.
... Many toxic compounds in UCG wastewater are challenging to decompose if only biological methods are used [130]. Thomas et al. present the possibility of phenol removal from UCG effluents by using coagulation-flocculation and the H 2 O 2 /UV process [131]. Treatment of coal gasification wastewater by catalytic oxidation with trace ozone is another promising technique [132]. ...
The underground coal gasification (UCG) technology converts coal into product gas and provides the option of environmentally and economically attractive coal mining. Obtained syngas can be used for heating, electricity, or chemical production. Numerous laboratory coal gasification trials have been performed in the academic and industrial fields. Lab-scale tests can provide insight into the processes involved with UCG. Many tests with UCG have been performed on ex situ reactors, where different UCG techniques, the effect of gasification agents, their flow rates, pressures, and various control mechanisms to improve gasification efficiency and syngas production have been investigated. This paper provides an overview of recent research on UCG performed on a lab scale. The study focuses on UCG control variables and their optimization, the effect of gasification agents and operating pressure, and it discusses results from the gasification of various lignites and hard coals, the possibilities of steam gasification, hydrogen, and methane-oriented coal gasification, approaches in temperature modeling, changes in coal properties during gasification, and environmental risks of UCG. The review focuses on laboratory tests of UCG on ex situ reactors, results, and the possibility of knowledge transfer to in situ operation.
... Moreover, investigations on the detection and remediation of phenols using various techniques have been employed. These include conventional techniques of coagulation and flocculation [62,63], solvent extraction [64], reverse and forward osmosis [65,66], membrane technologies [67,68], photocatalytic degradation [69,70] and electrochemical oxidations [71,72]. However, most of these methods suffer from major drawbacks, partly due to the lower solubility of the compounds. ...
The wide spread of phenols and their toxicity in the environment pose a severe threat to the existence and sustainability of living organisms. Rapid detection of these pollutants in wastewaters has attracted the attention of researchers from various fields of environmental science and engineering. Discoveries regarding materials and method developments are deemed necessary for the effective detection and remediation of wastewater. Although various advanced materials such as organic and inorganic materials have been developed, secondary pollution due to material leaching has become a major concern. Therefore, a natural-based material is preferable. Clay is one of the potential natural-based sorbents for the detection and remediation of phenols. It has a high porosity and polarity, good mechanical strength, moisture resistance, chemical and thermal stability, and cation exchange capacity, which will benefit the detection and adsorptive removal of phenols. Several attempts have been made to improve the capabilities of natural clay as sorbent. This manuscript will discuss the potential of clays as sorbents for the remediation of phenols. The activation, modification, and application of clays have been discussed. The achievements, challenges, and concluding remarks were provided.
... From previous studies [14], we know that UV/free chlorine advanced oxidation process can reduce the concentration of pollutants in water, but the oxidation effect is affected by various background components in the water body, such as HCO 3 -/CO 3 2-, chloride ions, natural organic matter, etc. As an emerging advanced oxidation degradation method based on the generation of Cl•, ClO•, and HO• radicals for oxidation, UV/free chlorine has shown good performance and considerable prospect for the removal of pollutants in the water body. ...
... They also have complex aromatic structures 19 making it costly to treat such textile effluents using conventional decontamination technologies 4 . Different conventional processes have been employed for elimination of dyes and phenolics from wastewater are such as ozonation 20,21,22 , ion exchange 23,24 , precipitation 25 , coagulation-flocculation 26 , photocatalytic degradation 27,28,29,30 , electrochemical methods 31,32 and adsorption 13,33 . Among them, adsorption technique have remained the most effective technique because of its effectiveness, simplicity and economical in water purification 34 . ...
Consumption of water contaminated with dyes and phenolic compounds is detrimental to human and animal wellbeing even at permissible limits. Therefore, their decontamination from water is important for the safety of consumers. Conventional water treatment techniques such as ozonation, ion exchange among others are expensive and ineffective. Adsorption as an emerging technique has gained research interest because of its ease in design, environmentally friendly and availability of materials as adsorbents in large quantities. The application of various adsorbents have extensively been reported for decontamination of dyes and phenolic compounds in wastewater such as 4-chlorophenol, Metanil Yellow (MY) dye, Phenol, Methyl green dye, Bromothymol Blue dye, Crystal violet, Methylene blue and Direct Blue 71. It has also been reported that adsorption by column continuous processes are more efficient than batch as it can be used continuously under high effluent flow rates in many pollution control processes in an industrial set up. The fixed bed column adsorption data is analyzed at different column conditions of bed height, pH, particle size, concentration and flow rate using different kinetic models such as Bohart-Adams, Thomas, Yoon-Nelson, Clark, Bed depth service time and Wolborska models amongst others to determine the column performance. The present paper involves a mini review of dynamics of fixed-bed column studies for removal of selected dyes and phenolics from a synthetic media.
... A large number of toxic compounds present in UCG wastewater are difficult to decompose if only biological methods are used [23]. Thomas et al. presents the possibility of phenol removal from UCG effluents by using coagulation-flocculation and the H2O2/UV Process [24]. Treatment of coal gasification wastewater by catalytic oxidation with trace ozone is another promising technique [25]. ...
... In recent years there have been several new developments involving biological coupling processes to treat coal gasification wastewater. Biological coupling treatment methods including: conventional biological processes, the combination of adsorption and biotechnology processes, biological enhancement technologies, co-metabolism technologies and the combination of advanced oxidation and biotechnology [23][24][25][26][27][28][29][30]. The development of an appropriate treatment method to remove pollutants from UCG wastewater is of utmost importance for the successful implementation of this technology. ...
One of the most important issues during UCG process is wastewater production and treatment. Condensed gasification wastewater is contaminated by many hazardous compounds. The composition of the generated UCG-derived wastewater may vary depending on the type of gasified coal and conditions of the gasification process. The main purpose of this study was a qualitative and quantitative characterization of the UCG wastewater produced during four different UCG experiments. Experiments were conducted using semi-anthracite and bituminous coal samples at two distinct pressures, i.e., 20 and 40 bar. The conducted studies revealed significant relationships between the physicochemical composition of the wastewater and the coal properties as well as the gasification pressure. The strongest impact is noticeable in the case of organic pollutants, especially phenols, BTEX and PAH’s. The most abundant group of pollutants were phenols. Conducted studies showed significantly higher concentration levels for bituminous coal: 29.25–49.5 mg/L whereas for semi-anthracite effluents these concentrations were in much lower range 2.1–29.7 mg/L. The opposite situation occurs for BTEX, higher concentrations were in wastewater from semi-anthracite gasification: 5483.1–1496.7 µg/L, while in samples from bituminous coal gasification average BTEX concentrations were: 2514.3–1354.4 µg/L. A similar relationship occurs for the PAH’s concentrations. The higher values were in case of wastewater from semi-anthracite coal experiments and were in range 362–1658 µg/L while from bituminous coal gasification PAH’s values are in lower ranges 407–1090 µg/L. The studies conducted have shown that concentrations of phenols, BTEX and PAH’s decrease with increasing pressure. Pearson’s correlation analysis was performed to enhance the interpretation of the obtained experimental data and showed a very strong relationship between three parameters: phenols, volatile phenols and CODcr.
... In recent years, response surface methodology -which is able to reveal both the effect of the independent variables on oxidation performance and the interaction between the variables by a minimal number of experiments and in minimal time-is being used in modeling contaminant removal from wastewaters through AOPs, and the central composite design (CCD) is one of the most popular designs of response surface methodology. The CCD method has been applied for estimation of second-order polynomial models in removal of contaminants from different wastewaters through the Fenton process in many studies (Abedinzadeh et al. 2018;Thomas et al. 2017Thomas et al. , 2018Thomas and Zdebik 2019;Kliś et al. 2019), but there is a dearth in the literature about using CCD in studies related to increasing the treatability or biological degradability of membrane concentrate of leachate. ...
The primary aim of this study is inert COD removal from leachate nanofiltration concentrate because of its high concentration of resistant organic pollutants. Within this framework, this study focuses on the treatability of leachate nanofiltration concentrate through Fenton oxidation and optimization of process parameters to reach the maximum pollutant removal by using response surface methodology (RSM). Initial pH, Fe2+ concentration, H2O2/Fe2+ molar ratio and oxidation time are selected as the independent variables, whereas total COD, color, inert COD and UV254 removal are selected as the responses. According to the ANOVA results, the R2 values of all responses are found to be over 95%. Under the optimum conditions determined by the model (pH: 3.99, Fe2+: 150 mmol/L, H2O2/Fe2+: 3.27 and oxidation time: 84.8 min), the maximum COD removal efficiency is determined as 91.4% by the model. The color, inert COD and UV254 removal efficiencies are determined to be 99.9%, 97.2% and 99.5%, respectively, by the model, whereas the total COD, color, inert COD and UV254 removal efficiencies are found respectively to be 90%, 96.5%, 95.3% and 97.2%, experimentally under the optimum operating conditions. The Fenton process improves the biodegradability of the leachate NF concentrate, increasing the BOD5/COD ratio from the value of 0.04 to the value of 0.4. The operational cost of the process is calculated to be 0.238 €/g CODremoved. The results indicate that the Fenton oxidation process is an efficient and economical technology in improvement of the biological degradability of leachate nanofiltration concentrate and in removal of resistant organic pollutants.
... These problems relate to, for example, wastewater from the electroplating and electronics industries, due to the presence of heavy metal ions [4][5][6], and the textile industry, which uses many dyes of varying chemical structures, including toxic azo dyes, which may adversely affect aquatic organisms by preventing the penetration of light and oxygen into the deeper layers of water and thus may adversely affect the proper functioning and development of aquatic organisms [7][8][9][10]. Other examples include the coke industry which produces polluted wastewater by, for example, oils, tars, phenols, ammonia, thiocyanates, cyanides, sulphides and PAHs [11][12][13], the tanning industry [14] and many others. For both water and industrial wastewater, one of the basic technological processes used for their treatment is coagulation, in which the particles of the dispersed colloid phase form larger aggregates creating a continuous phase, with a complicated and irregular spatial structure. ...
... Coagulation can also be an intermediate level of industrial wastewater treatment. In this case, it is usually used before exerting more advanced methods of purification, such as: advanced oxidation processes (e.g., the Fenton method) or biological processes (e.g., use of activated sludge) [13,15]. In this aspect, coagulation has a special connection with the protection of water resources. ...
... Tests of the dependence of Ti concentration in water on the coagulation pH, carried out with the use of TiCl 4 solutions, showed that the concentration of titanium in water after the coagulation process varies in the range of 0.007-1.200 mg/L, at pH 2-10 with application of a dose of Ti 100 mg/L [13]. In addition, titanium and its compounds are biologically inert, and therefore, water containing titanium compounds is safe, and residual concentrations greater than the maximum acceptable concentration are safe and are not a risk factor for Alzheimer's disease or hemochromatosis, as is the case (under certain conditions) when using aluminum and iron coagulants [31]. ...
Coagulation is a fundamental process of water treatment. Its main purpose is to remove colour and turbidity from water and it plays a role in ensuring the safety of the water supply systems. It can also be an intermediate stage of industrial wastewater treatment and is usually used before applying more complex treatment methods. The protection of water resources, which will re-enter the water cycle, is of vital importance. Research conducted in recent years indicates the possibility of using coagulants containing Ti 4+ compounds as an alternative to traditional coagulants. In addition, the use of titanium coagulants provides the opportunity to recycle reagents, as it is possible to recover titanium from the resultant sludge. A review of available literature data on the use of titanium salts in the coagulation process was carried out in the paper. The work covers both issues of water and industrial wastewater treatment. The results of tests conducted using various parameters of the coag-ulation process were considered. The research on the coagulation of synthetic water and river water as well as synthetic sewage and sewage from various industrial processes was collated and analyzed.
... The extensive effort has been devoted to developing various cost-effective and environmentally friendly processes to removal of hazardous and refractory organic compunds from the wastewater. So far, integrated engineering systems including biological and chemical advanced treatment system as holistic approach have been considered to clean up of UCG wastewater [2,[8][9][10]. The development of an appropriate treatment method to remove pollutants from UCG wastewater is extremly important for the successful application of UCG technology in energy transformation. ...
With the rapid pace of industrialization and urbanization, the environmental safety of soil is a worldwide concern. In China alone, one-fifth of the arable land is reported to be contaminated with heavy metals including nickel. In this review, current research on nickel remediation, specifically the various remediation technologies including physical and chemical remediation methods, such as immobilization, soil washing, encapsulation, soil replacement, and electrokinetic methods; phytoremediation; and bioremediation, is summarized. Further, the mechanisms underlying the presented remediation technologies, along with their advantages and disadvantages, are discussed. The lacunae in available technologies for nickel remediation are also briefly discussed. The review concludes with a scheme for successful soil remediation.
