Special Issue "Wastewater Treatment Processes"

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Biological Systems".

Deadline for manuscript submissions: 31 March 2019

Special Issue Editors

Guest Editor
Prof. Dr. Kostas A. Matis

Laboratory of Chemical and Environmental Technology, Department of Chemistry, Aristotle University, GR-541 24 Thessaloniki, Greece
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Interests: separation science and technology (flotation); wastewater treatment; environmental biotechnology; inorganic materials; mineral processing
Guest Editor
Assoc. Prof. George Z. Kyzas

Hephaestus Advanced Laboratory, Eastern Macedonia and Thrace Institute of Technology, Kavala, Greece
Website | E-Mail
Interests: wastewater treatment; polymers; decontamination; materials; sorption; nanobubbles; transportation phenomena

Special Issue Information

Dear Colleagues,

Cheap and plentiful, water was for centuries a manufacturing tool that industry took for granted. However, population growth, globalization, and climate change are shepherding in a new water-constrained era. The food-chain pyramid may receive contaminants of either surface water or ground water around industrial and residential communities (e.g., metals, pesticides, pharmaceuticals, etc.) through man’s activities and on top of the pyramid, man (perhaps) receives pre-concentrated toxicity. A common example constitutes Bangladesh, where millions of people consumed drinking water with arsenic concentrations—exceeding the guideline values of WHO. Good, clean water just cannot be replaced—and it is becoming harder to come by. Typical processes that are investigated and applied to wastewater treatment can be the following: Biological, adsorption, flocculation, oxidation, membranes, filtration, and so on, including the nanotechnological. This Special Issue on “Wastewater Treatment Processes” seeks high-quality works and topics (not only those) focusing on the latest novel wastewater processes, including biological, adsorption, flocculation, oxidation, membranes, filtration, etc.

Prof. Dr. Kostas A. Matis
Dr. George Z. Kyzas
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1100 CHF (Swiss Francs). Please note that for papers submitted after 30 June 2019 an APC of 1200 CHF applies. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • wastewaters
  • water
  • adsorption
  • membranes
  • oxidation
  • flocculation
  • flotation
  • filtration

Published Papers (19 papers)

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Open AccessArticle Flocculation of a High-Turbidity Kaolin Suspension Using Hydrophobic Modified Quaternary Ammonium Salt Polyacrylamide
Processes 2019, 7(2), 108; https://doi.org/10.3390/pr7020108
Received: 25 January 2019 / Revised: 11 February 2019 / Accepted: 12 February 2019 / Published: 18 February 2019
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Abstract
In this work, a novel cationic polyacrylamide (PAMD) was synthesized by acrylamide (AM) diallyl dimethyl ammonium chloride (DMD) and dodecyl polyglucoside (DPL) under low-pressure ultraviolet (UV) initiation. The intrinsic viscosity and cationic degree of PAMD were optimized in copolymerization. The optimum synthesis conditions [...] Read more.
In this work, a novel cationic polyacrylamide (PAMD) was synthesized by acrylamide (AM) diallyl dimethyl ammonium chloride (DMD) and dodecyl polyglucoside (DPL) under low-pressure ultraviolet (UV) initiation. The intrinsic viscosity and cationic degree of PAMD were optimized in copolymerization. The optimum synthesis conditions that affect polymerization were determined to be solid content 30%, DPL content 25%, DMD content 30%, illumination time 135 min, and pH 9. The flocculation performance of flocculant PAMD with a high cationic degree was investigated in the purification of high-turbidity water. The flocculation mechanism was correspondingly studied and summarized based on Fourier transform-infrared (FTIR) analysis. Finally, the results of an experimental simulation using the response surface method show that 98.9% supernatant transmittance was achieved under dosage 4 mg/L, fast stirring time 20 min, pH 7, and stirring speed 320 rpm. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Adsorption of Organic Constituents from Reverse Osmosis Concentrate in Coal Chemical Industry by Coking Coal
Processes 2019, 7(1), 44; https://doi.org/10.3390/pr7010044
Received: 20 November 2018 / Revised: 8 January 2019 / Accepted: 9 January 2019 / Published: 16 January 2019
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Abstract
To solve the unwieldy problem of coal chemical wastewater reverse osmosis concentrate (ROC), a novel treatment method in which coking coal was used to adsorb the organic from ROC and the adsorption mechanism involved was investigated. The results showed that the organic components [...] Read more.
To solve the unwieldy problem of coal chemical wastewater reverse osmosis concentrate (ROC), a novel treatment method in which coking coal was used to adsorb the organic from ROC and the adsorption mechanism involved was investigated. The results showed that the organic components in the ROC of coal chemical industry can be effectively absorbed by the coking coal and the total organic carbon, UV254 and chromaticity of treated ROC reduced by 70.18%, 70.15% and 59.55%, respectively, at the coking coal dosage of 80 g/L. The isothermal adsorption data were fitted to the Langmuir model well. The kinetics were expressed well by the quasi-second-order kinetic model. The intragranular diffusion model and the BET (Acronym for three scientists: Brunauer–Emmett–Teller) test showed that the adsorption occurred mainly on the surface of the coking coal and its macropores and mesopores. When the pollutants further diffused to the mesopores and micropores, the adsorption rate decreased. The result of X-ray photoelectron spectroscopy and fourier transform infrared spectroscopy spectra showed that the coking coal mainly adsorbed the nitrogen and oxygen species and the halogenated hydrocarbon organic compounds in the ROC. The chlorinated hydrocarbons and heterocyclic organics in ROC are adsorbed on the surface of coking coal. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Efficient Removal of Hexavalent Chromium from Wastewater with Electro-Reduction
Processes 2019, 7(1), 41; https://doi.org/10.3390/pr7010041
Received: 19 December 2018 / Revised: 8 January 2019 / Accepted: 9 January 2019 / Published: 15 January 2019
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Abstract
Removal of hexavalent chromium had attracted much attention as it is a hazardous contaminant. An electrocoagulation-like technology electro-reduction was applied. The chromium (VI) in the wastewater was reduced to chromium (III) by the electron supplied by electricity power and Fe2+, formed [...] Read more.
Removal of hexavalent chromium had attracted much attention as it is a hazardous contaminant. An electrocoagulation-like technology electro-reduction was applied. The chromium (VI) in the wastewater was reduced to chromium (III) by the electron supplied by electricity power and Fe2+, formed from corrosion of steel electrodes in acidic conditions. The mechanism and parameters affecting the reaction were investigated. The results optimized by response surface methodology indicated that the influence of single factor on the reduction efficiency followed the order: A: dosage of H2SO4 > C: reaction time > D: reaction temperature > B: current intensity. The reduction efficiency was hardly affected by current intensity, while it was increased with the increasing of reaction time and acid concentration. The reducing agent, Fe2+ an and extra free electron, acted as a reducing agent and could easily reduce hexavalent chromium to trivalent chromium at high temperatures in an acidic medium. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessFeature PaperArticle Effective Dye Degradation by Graphene Oxide Supported Manganese Oxide
Processes 2019, 7(1), 40; https://doi.org/10.3390/pr7010040
Received: 1 December 2018 / Revised: 28 December 2018 / Accepted: 11 January 2019 / Published: 14 January 2019
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Abstract
Graphene oxide (GO) was used as a support for manganese oxide (MnO2) for the preparation of a nanocomposite catalyst for the degradation of an azo dye, Reactive Black 5 (RB5). The nanocomposite was characterized for the structure by XRD, for the [...] Read more.
Graphene oxide (GO) was used as a support for manganese oxide (MnO2) for the preparation of a nanocomposite catalyst for the degradation of an azo dye, Reactive Black 5 (RB5). The nanocomposite was characterized for the structure by XRD, for the morphology with SEM, and for the surface chemistry with FTIR and potentiometric titration measurements. The GO-MnO2 nanocomposite presented a high catalytic activity for the degradation/oxidation of RB5 at ambient conditions, which was higher than that of the pure MnO2 and could be attributed to the beneficial contribution of the manganese oxide and the graphene oxide. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Textile Wastewater Treatment for Water Reuse: A Case Study
Processes 2019, 7(1), 34; https://doi.org/10.3390/pr7010034
Received: 11 December 2018 / Revised: 30 December 2018 / Accepted: 3 January 2019 / Published: 11 January 2019
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Abstract
The reduced natural waters and the large amount of wastewater produced by textile industry necessitate an effective water reuse treatment. In this study, a combined two-stage water reuse treatment was established to enhance the quality and recovery rate of reused water. The primary [...] Read more.
The reduced natural waters and the large amount of wastewater produced by textile industry necessitate an effective water reuse treatment. In this study, a combined two-stage water reuse treatment was established to enhance the quality and recovery rate of reused water. The primary treatment incorporated a flocculation and sedimentation system, two sand filtration units, an ozonation unit, an ultrafiltration (UF) system, and a reverse osmosis (RO) system. The second treatment included an ozonation unit, a sand filtration unit, and UF and RO systems. The color removal rate increased with the increasing ozone dosage, and the relational expression between the ozone dosage and color removal rate was fitted. Ozonation greatly reduced the color by 92.59 and 97.27 times during the primary and second ozonation stages, respectively. RO had the highest removal rate. The combined processes showed good performance in water reuse treatment. The treated, reused water satisfied the reuse standard and surpassed the drinking water standard rates for chemical oxygen consumption (CODcr), color, NH3-N, hardness, Cl, SO42−, turbidity, Fe3+, and Cu2+. The operating cost of reuse water treatment was approximately 0.44 USD·m−3. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle A New Method for the Process Division and Effect Evaluation of Coagulation Based on Particle Size Fractal Dimension
Processes 2018, 6(12), 237; https://doi.org/10.3390/pr6120237
Received: 22 October 2018 / Revised: 18 November 2018 / Accepted: 20 November 2018 / Published: 23 November 2018
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Abstract
To divide, control, and predict the effects of the coagulation process in water treatment, a characteristic analysis of the change in particle size distribution (particle number and fractal dimension) during aided coagulation with hydrated MnO2 was performed. The results showed that the [...] Read more.
To divide, control, and predict the effects of the coagulation process in water treatment, a characteristic analysis of the change in particle size distribution (particle number and fractal dimension) during aided coagulation with hydrated MnO2 was performed. The results showed that the process of coagulation could be divided into three characteristic stages based on the first derivative of the particle size fractal dimension. In the primary stage, most of the microflocs aggregated to form small flocs; in the growth stage, most of the small flocs aggregated to form large flocs; and in the stable stage, some large flocs broke apart and reformed. The first derivative of the particle size fractal dimension had a good linear relationship with the coagulation time in the primary stage and growth stage, and its slope had a power function relationship with the particle number in settled water; the first derivative could thus be used to evaluate the coagulation effect. In the stable stage, the rate of change in particle size fractal dimension fluctuated along the fitted line, and the mean residual sum of squares had a linear relation with the particle number in settled water; therefore, this parameter could be used as an indicator of the coagulation effect. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Preparation, Characterization, and Sludge Conditioning of Cationic Polyacrylamide Synthesized by a Novel UVA-Initiated System
Processes 2018, 6(12), 233; https://doi.org/10.3390/pr6120233
Received: 30 October 2018 / Revised: 18 November 2018 / Accepted: 19 November 2018 / Published: 22 November 2018
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Abstract
Controlling the concentration of free radicals in polymerization systems is advantageous for preparing cationic polyacrylamide (CPAM) with a high molecular weight and acceptable dissolvability. In this study, a novel ultraviolet (UVA)-initiated system characterized by an adjustable light intensity and a redox-azo complex initiator [...] Read more.
Controlling the concentration of free radicals in polymerization systems is advantageous for preparing cationic polyacrylamide (CPAM) with a high molecular weight and acceptable dissolvability. In this study, a novel ultraviolet (UVA)-initiated system characterized by an adjustable light intensity and a redox-azo complex initiator was used to synthesize a CPAM flocculant named NP. Comparatively, another CPAM flocculant named SP with a stable UVA light intensity and a single initiator was prepared. Their chemical structure, morphology, and thermal stability were analyzed through instrumental analysis. 1H NMR indicated that NP was successfully prepared, and a small fraction of a cationic homopolymer was mixed in the product. Polymerization conditions of NP were optimized, and polymerization mechanism was determined by investigating the effects of various parameters on intrinsic viscosity, conversion, and dissolvability. Results showed that the best performance was obtained at indices of 0.45 wt‰ redox initiator concentration, 0.2 wt‰ azo initiator concentration, 40.0 wt% cationic monomer, 3 wt‰ urea, and first- and second-stage light intensities of 8.5 and 13 mW/cm2, respectively. The sludge conditioning performances of NP and SP were comparatively evaluated, and the mechanism was determined by examining sedimentation behavior and floc size distribution. High intrinsic viscosity, porous morphology structure, and mixed NP cationic homopolymer contributed to the improvement of sludge conditioning performance. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Fault Detection in Wastewater Treatment Systems Using Multiparametric Programming
Processes 2018, 6(11), 231; https://doi.org/10.3390/pr6110231
Received: 28 August 2018 / Revised: 30 October 2018 / Accepted: 12 November 2018 / Published: 20 November 2018
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Abstract
In this work, a methodology for fault detection in wastewater treatment systems, based on parameter estimation, using multiparametric programming is presented. The main idea is to detect faults by estimating model parameters, and monitoring the changes in residuals of model parameters. In the [...] Read more.
In this work, a methodology for fault detection in wastewater treatment systems, based on parameter estimation, using multiparametric programming is presented. The main idea is to detect faults by estimating model parameters, and monitoring the changes in residuals of model parameters. In the proposed methodology, a nonlinear dynamic model of wastewater treatment was discretized to algebraic equations using Euler’s method. A parameter estimation problem was then formulated and transformed into a square system of parametric nonlinear algebraic equations by writing the optimality conditions. The parametric nonlinear algebraic equations were then solved symbolically to obtain the concentration of substrate in the inflow, S c i n , inhibition coefficient, K i , and specific growth rate, μ o , as an explicit function of state variables (concentration of biomass, X ; concentration of organic matter, S c ; concentration of dissolved oxygen, S o ; and volume, V ). The estimated model parameter values were compared with values from the normal operation. If the residual of model parameters exceeds a certain threshold value, a fault is detected. The application demonstrates the viability of the approach, and highlights its ability to detect faults in wastewater treatment systems by providing quick and accurate parameter estimates using the evaluation of explicit parametric functions. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Alternative Approach to Current EU BAT Recommendation for Coal-Fired Power Plant Flue Gas Desulfurization Wastewater Treatment
Processes 2018, 6(11), 229; https://doi.org/10.3390/pr6110229
Received: 18 October 2018 / Revised: 12 November 2018 / Accepted: 14 November 2018 / Published: 19 November 2018
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Abstract
Fossil fuel combustion is a serious environmental problem. Significant quantities of flue gasses and wastewater, requiring further treatment, are produced. This article compares three wet flue gas desulfurization (FGD) wastewater treatment methods: coagulation with precipitation using iron(III) ions—recommended by the European Union as [...] Read more.
Fossil fuel combustion is a serious environmental problem. Significant quantities of flue gasses and wastewater, requiring further treatment, are produced. This article compares three wet flue gas desulfurization (FGD) wastewater treatment methods: coagulation with precipitation using iron(III) ions—recommended by the European Union as the best available technique (BAT)—and two alternative advanced oxidation processes (Fe2+/H2O2 and Fe0/H2O2). Both oxidation processes that were used met the technical FGD wastewater treatment requirements of the BAT. The best treatment effects, expressed as pollutants’ removal, were obtained for the Fe2+/H2O2 process for 150/300 mg/L reagent doses. It allows effective removal of boron up to 212 mg/L and heavy metals up to below the detection limit <0.010 mg/L for Pb and <0.005 mg/L for Cu. Therefore, the Fe2+/H2O2 process could be an option for FGD wastewater treatment as an alternative to the BAT recommended iron(III)-based coagulation with precipitation. Additionally, an analysis of variance was applied to check the significance of the two independent variables and their interactions. Statistical analysis confirmed high efficiency and applicability of treatment process. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Statistical Analysis of Circulating Water Quality Parameters under Variable-Frequency Vertical Electromagnetic Fields
Processes 2018, 6(10), 182; https://doi.org/10.3390/pr6100182
Received: 7 September 2018 / Revised: 29 September 2018 / Accepted: 1 October 2018 / Published: 2 October 2018
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Abstract
No unified electromagnetic anti-fouling mechanism is currently available. Most research has focused on the effects of structural parameters and water quality parameters on electromagnetic fields; variations in water quality parameters under the influence of electromagnetic fields have not been reported. A variable-frequency vertical [...] Read more.
No unified electromagnetic anti-fouling mechanism is currently available. Most research has focused on the effects of structural parameters and water quality parameters on electromagnetic fields; variations in water quality parameters under the influence of electromagnetic fields have not been reported. A variable-frequency vertical electromagnetic field is proposed in this study. Relationships between conductivity, pH value, dissolved oxygen, turbidity, fouling resistance, and magnetic acting time were carefully analyzed using statistical analysis. Results show that the conductivity difference was the most explanatory predictive variable on magnetic acting time in the multiple stepwise regression model. Magnetic acting time has a greater impact on conductivity than pH value and dissolved oxygen. Conductivity is used as an adaptive feedback control parameter for the optimum anti-fouling state. Fouling resistance on the heat-exchanging surface of the magnetic experiment was smaller than that of the contrast experiment. The anti-fouling efficiency in 1 kHz and 5 kHz magnetic and contrast experiments was 91.23% and 46.97%, respectively. Better anti-fouling performance was realized under the influence of low-frequency electromagnetic fields, confirming that physical water treatment is an effective and environmentally friendly method to eliminate heat exchanger fouling. This research serves as a reference for the development of an electromagnetic-adaptive closed-loop water treatment device. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Influence of Organic Ligands on the Colloidal Stability and Removal of ZnO Nanoparticles from Synthetic Waters by Coagulation
Processes 2018, 6(9), 170; https://doi.org/10.3390/pr6090170
Received: 1 September 2018 / Revised: 14 September 2018 / Accepted: 15 September 2018 / Published: 17 September 2018
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Abstract
The large-scale production and usage of zinc oxide nanoparticles (ZnO NPs) may lead to their post-release into the aquatic environment. In this study, the effect of hydrophobic/hydrophilic organic ligands on sorption and sedimentation of ZnO NPs has been systematically investigated. In addition, the [...] Read more.
The large-scale production and usage of zinc oxide nanoparticles (ZnO NPs) may lead to their post-release into the aquatic environment. In this study, the effect of hydrophobic/hydrophilic organic ligands on sorption and sedimentation of ZnO NPs has been systematically investigated. In addition, the coagulation efficiency of ZnO NPs, Zn2+, dissolved organic carbon (DOC), and UV254 with varying ferric chloride (FC) dosages in synthetic waters were also evaluated. The results showed that the higher concentration of organic ligands, i.e., humic acid (HA), salicylic acid (SA), and L-cysteine (L-cys) reduced the ζ-potential and hydrodynamic diameter (HDD) of particles, which enhanced the NPs stability. The adsorption of organic ligands onto ZnO NPs was fitted with the Langmuir model, with maximum adsorption capacities of 143, 40.47, and 66.05 mg/g for HA, SA and L-cys respectively. Removal of up to 95% of ZnO NPs and Zn2+ was achieved in studied waters at the effective coagulation zone (ECR), above which excess charge induced by coagulant restabilized the NPs in suspension. Moreover, the removal rate of DOC and UV254 were found to be higher in hydrophobic waters than hydrophilic waters. The width of ECR strongly depends on the characteristics of source water. The waters with hydrophobic ligand and higher UV254 values require more coagulant than hydrophilic waters to achieve the similar ZnO NPs and Zn2+ removal. The results of Fourier transform infrared (FT-IR) analysis of ZnO NPs composite contaminant flocs indicated that the combined effect of enmeshment and charge neutralization might be a possible removal mechanism. These findings may facilitate the prediction of fate, transport, and removal of ZnO NPs in the natural waters, and might contribute to risk assessment, as well as decision making about engineered nanoparticles (ENPs) in aquatic systems. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessFeature PaperArticle Basic Dye Removal with Sorption onto Low-Cost Natural Textile Fibers
Processes 2018, 6(9), 166; https://doi.org/10.3390/pr6090166
Received: 30 August 2018 / Revised: 10 September 2018 / Accepted: 12 September 2018 / Published: 14 September 2018
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Abstract
Over the last several years, the trend of researchers has been to use some very low-cost materials as adsorbents. For this purpose, some already commercially used bast fibers were selected as potential adsorbent materials to remove basic dye from synthetic effluents. The adsorption [...] Read more.
Over the last several years, the trend of researchers has been to use some very low-cost materials as adsorbents. For this purpose, some already commercially used bast fibers were selected as potential adsorbent materials to remove basic dye from synthetic effluents. The adsorption of basic yellow 37 dye was studied using three different bast fibers under the names of flax, ramie, and kenaf. Their morphological structure was examined using several techniques such as scanning electron microscopy (SEM), crystallinity, X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), as well as those characterizations being a useful tool to propose a mechanism of the whole adsorption process. The adsorption evaluation was achieved by studying at first the pH (12) and temperature effects (25–55 °C). Two isotherm models (Langmuir and Freundlich) were also applied to the experimental equilibrium data revealing the superiority of ramie fibers (327, 435, and 460 mg·g−1 (25 °C) for kenaf, flax, and ramie, respectively). The crucial adsorbent’s dosage was found to be 0.1 g per litre for all fibers, while the completed desorption study (eluant’s pH and reuse cycles) also confirmed the strong potential of these kinds of fibers as adsorbents. The latter may be attributed to the cellulosic content. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Modelling Nutrients and Organics Removal by Biological Slow Filtration in Micro-Polluted Water Source Treatment
Processes 2018, 6(8), 128; https://doi.org/10.3390/pr6080128
Received: 17 July 2018 / Revised: 7 August 2018 / Accepted: 8 August 2018 / Published: 15 August 2018
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Abstract
The biological slow filtration (BSF) system as a simple and efficient environmental technology has been widely applied in treatment of ‘micro-polluted’ water. At present, many related studies have focused on the removal efficiency of biological indicators (such as bacteria and viruses). However, there [...] Read more.
The biological slow filtration (BSF) system as a simple and efficient environmental technology has been widely applied in treatment of ‘micro-polluted’ water. At present, many related studies have focused on the removal efficiency of biological indicators (such as bacteria and viruses). However, there is less research on the removal performance of nutrients and organics in the BSF system. In this paper, we employed a lab-scale biological slow filter to study the removal efficiency and degradation mechanism of nutrients and organics. We proved through adsorption of filter layer at the early running stage and biodegradation at the later stage, the BSF system could achieve effective removal of NH3-N, TN, TP, CODMn and turbidity and the corresponding removal rates are 83.65%, 42.45%, 42.94%, 60.41% and 83.55%, respectively. Furthermore, we also explored the influence of four main factors (filtration rate, filter depth, hydraulic head and temperature) and their interactions on removal rates of nutrients and organics in the BSF system and obtained the optimal operating parameters as follows: filtration rate 0.1 m/h, filter depth 0.8 m, hydraulic head 0.64 m, temperature 26.06 °C. This study would provide a theoretical foundation for the actual application of biological slow filter in treatment of micro-polluted water in developing countries and offer an optimized basis for the design of operating conditions. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Preparation and Characterization of Polyaluminum Titanium Silicate and its Performance in the Treatment of Low-Turbidity Water
Processes 2018, 6(8), 125; https://doi.org/10.3390/pr6080125
Received: 17 July 2018 / Revised: 7 August 2018 / Accepted: 8 August 2018 / Published: 11 August 2018
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Abstract
Using conventional coagulant, low turbidity water is difficult to achieve standard. This research uses aluminum chloride, titanium tetrachloride, and sodium silicate as raw materials for the preparation of polyaluminum titanium silicate chloride (PATC). PATC is used to treat low turbidity. The synthetic PATC [...] Read more.
Using conventional coagulant, low turbidity water is difficult to achieve standard. This research uses aluminum chloride, titanium tetrachloride, and sodium silicate as raw materials for the preparation of polyaluminum titanium silicate chloride (PATC). PATC is used to treat low turbidity. The synthetic PATC showed the best coagulating effect in treated water under the following experimental conditions: Reaction temperature of 50 °C, and n(Ti)/n(Al), n(-OH)/n(Ti+Al), and n(Si)/n(Ti+Al) were 0.3, 0.2, and 1.0, respectively. The species distribution and the transformation of PATC showed that the interaction between titanium tetrachloride, sodium silicate, and the hydrolysate of Al influenced the morphology distribution of Al. Temperature and -OH greatly affected the distribution of Alb in PATC. The analysis of infrared spectra and X-ray diffraction indicated that both titanium tetrachloride and sodium silicate had complex chemical reactions with aluminum chloride. Si-O-Ti and Si-O-Al produced by the reaction affected the PATC treatment of low-turbidity water. Scanning electron microscopy showed, that compared with polyaluminum chloride(PAC), the PATC cluster was more compact, showed greater pore structure, and presented better flocculation precipitation. The optimal reaction conditions were an initial turbidity of 10 nephelometric turbidity unit(NTU), PATC dosage of 9 mg/L, pH of 8 for the simulated water sample, stirring speed of 50 r/min, and settling time of 50 min, which were determined by Orthogonal experiment. The zeta potential of the reaction process was analyzed. In the treatment of low-turbidity water, PATC mainly functioned by adsorbing, bridging, and sweeping flocculation. Electrical neutralization played an auxiliary role. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Treatment of Oil-Contaminated Water by Modified Polysilicate Aluminum Ferric Sulfate
Processes 2018, 6(7), 95; https://doi.org/10.3390/pr6070095
Received: 23 June 2018 / Revised: 16 July 2018 / Accepted: 18 July 2018 / Published: 20 July 2018
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Abstract
In this experiment, a variety of inorganic materials were simply compounded with Polysilicate Aluminum Ferric Sulfate (PSAFS) to treat emulsified oil-contaminated water. Manganese sulfate (MnSO4), magnesium sulfate (MgSO4), and zinc sulfate (ZnSO4) were selected as the materials [...] Read more.
In this experiment, a variety of inorganic materials were simply compounded with Polysilicate Aluminum Ferric Sulfate (PSAFS) to treat emulsified oil-contaminated water. Manganese sulfate (MnSO4), magnesium sulfate (MgSO4), and zinc sulfate (ZnSO4) were selected as the materials to modify PSAFS in order to obtain a coagulant with good flocculation performance. During the preparation of modified PSAFS, metal manganese, magnesium, and zinc were introduced for modification, and four factors were used to optimize the best proportion of modifiers and PSAFS. The results showed that the order of demulsification and oil-removal ability is as follows: Mn-PSAFS (Mn-modified PSAFS) > Zn-PSAFS (Zn-modified PSAFS) > Mg-PSAFS (Mg-modified PSAFS) > PSAFS. Modified PSAFS was characterized by infrared spectroscopy (IR) and a Scanning Electron Microscope (SEM). In the range of 604 cm−1 to 1200 cm−1, due to the complexation reaction between metal ions and polysilicic acid, the absorption peaks of the modified PSAFS and PSAFS were significantly different. SEM results revealed that the particles of the spatial network structure were fibrous and arranged more closely (0.5 mm × 50.0 mm) than others. This study provided that the modified PSAFS had good potential application in treating emulsified oily wastewater in the future. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Synthesis and Characterization of Ampholytic Flocculant CPCTS-g-P (CTA-DMDAAC) and Its Flocculation Properties for Microcystis Aeruginosa Removal
Processes 2018, 6(5), 54; https://doi.org/10.3390/pr6050054
Received: 13 April 2018 / Revised: 4 May 2018 / Accepted: 8 May 2018 / Published: 11 May 2018
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Abstract
The ampholytic chitosan based flocculant carboxylated chitosan graft-(3-chloro-2-hydroxypropyl) trimethylammonium chloride-dimethyl diallyl ammonium chloride (CPCTS-g-P (CTA-DMDAAC)) was synthesized by photo polymerization using carboxylated chitosan (CPCTS), 3-chloro-2-chloropropyltrimethylammonium chloride (CTA) and dimethyldiallylammonium chloride (DMDAAC) as the cationic co-monomers. The effects of monomer concentration, the ratio of [...] Read more.
The ampholytic chitosan based flocculant carboxylated chitosan graft-(3-chloro-2-hydroxypropyl) trimethylammonium chloride-dimethyl diallyl ammonium chloride (CPCTS-g-P (CTA-DMDAAC)) was synthesized by photo polymerization using carboxylated chitosan (CPCTS), 3-chloro-2-chloropropyltrimethylammonium chloride (CTA) and dimethyldiallylammonium chloride (DMDAAC) as the cationic co-monomers. The effects of monomer concentration, the ratio of CPCTS and cationic monomers, cationic degree, initiator time, photoinitiator concentration, and pH value on the properties of CPCTS-g-P (CTA-DMDAAC) were studied. The microcystis aeruginosa that was cultured in laboratory was used for CPCTS-g-P (CTA-DMDAAC) flocculation tests. The effects of CPCTS-g-P (CTA-DMDAAC) dosage, pH value and G value on flocculation performance were investigated. The maximum removal rate of chlorophyll-a (Chl-a) and chemical oxygen demand (COD) that were obtained by CPCTS-g-P (CTA-DMDAAC) were 98.8% and 96.5% under the conditions of dosage 4 mg/L, pH 7 and G value 200 s−1, respectively. The flocculation experiments showed that chitosan-based flocculant CPCTS-g-P (CTA-DMDAAC) had better flocculation performance than commercially available flocculants cationic polyacrylamide (CPAM), Polyferric Sulfate (PFS), and polymeric aluminium (PAC). Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Review

Jump to: Research, Other

Open AccessReview Technology for the Remediation of Water Pollution: A Review on the Fabrication of Metal Organic Frameworks
Processes 2018, 6(8), 122; https://doi.org/10.3390/pr6080122
Received: 29 June 2018 / Revised: 22 July 2018 / Accepted: 3 August 2018 / Published: 8 August 2018
Cited by 3 | PDF Full-text (10746 KB) | HTML Full-text | XML Full-text
Abstract
The ineffective control of the release of pollutants into water has led to serious water pollution. Compared with conditions in the past, the polluting components in aquatic environments have become increasingly complex. Some emerging substances have led to a new threat to the [...] Read more.
The ineffective control of the release of pollutants into water has led to serious water pollution. Compared with conditions in the past, the polluting components in aquatic environments have become increasingly complex. Some emerging substances have led to a new threat to the safety of water. Therefore, developing cost-effective technologies for the remediation of water pollution is urgently needed. Adsorption has been considered the most effective operational unit in water treatment processes and thus adsorption materials have gained wide attention. Among them, metal organic frameworks (denoted as MOFs) have been rapidly developed in recent years due to their unique physicochemical performance. They are characterized by larger porosity and larger specific surface area, easier pore structure designing, and comfortable structural modification. In many fields such as adsorption, separation, storage, and transportation, MOFs show a better performance than conventional adsorption materials such as active carbon. Their performance is often dependent on their structural distribution. To optimize the use of MOFs, their fabrication should be given more attention, without being limited to conventional preparation methods. Alternative preparation methods are given in this review, such as diffusion, solvent thermal, microwave, and ion thermal synthesis. Furthermore, developing functionalized MOFs is an available option to improve the removal efficiencies of a specific contaminant through pre-synthetic modification and post-synthesis modification. Post-synthesis modification has become a recent research hotspot. The coupling of MOFs with other techniques would be another option to ameliorate the remediation of water pollution. On one hand, their intrinsic drawbacks may be reduced. On the other hand, their performance may be enhanced due to their interaction behaviors. Overall, such coupling technologies are able to enhance the performance of an individual material. Because the excellent performance of MOF materials has been widely recognized and their developments have received wide attention, especially in environmental fields, in the present work we provide a review of fabrication of MOFs so as to motivate readers to deepen their understanding of the use of MOFs. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessFeature PaperReview Flotation in Water and Wastewater Treatment
Processes 2018, 6(8), 116; https://doi.org/10.3390/pr6080116
Received: 9 July 2018 / Revised: 26 July 2018 / Accepted: 1 August 2018 / Published: 7 August 2018
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Abstract
Flotation constitutes a separation process that originated from mineral processing. Nowadays, wider applications have been found and compared to flotation for water and wastewater treatment. Stress in the present review paper was mainly applied to heavy metal ions recovery by flotation and the [...] Read more.
Flotation constitutes a separation process that originated from mineral processing. Nowadays, wider applications have been found and compared to flotation for water and wastewater treatment. Stress in the present review paper was mainly applied to heavy metal ions recovery by flotation and the respective mechanism followed, being either ion, precipitate, or sorptive flotation. In the latter case, the use of adsorbents is included (such as powdered activated carbon, zeolites, and goethite), as well as various biosorbents. The flotation of the following metals was reviewed: copper, zinc, nickel, lead, iron, chromium, arsenic, gold, and others. The bubble generation method could be applied for typical dispersed-air flotation column, electroflotation, or dissolved-air flotation; the latter being the most appropriate established technique in water treatment. The role of particle size (for example, studying flotation of salt-type mineral fines) was also examined. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Other

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Open AccessProject Report Full-Scale Processing by Anaerobic Baffle Reactor, Sequencing Batch Reactor, and Sand Filter for Treating High-Salinity Wastewater from Offshore Oil Rigs
Processes 2018, 6(12), 256; https://doi.org/10.3390/pr6120256
Received: 19 November 2018 / Revised: 30 November 2018 / Accepted: 4 December 2018 / Published: 9 December 2018
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Abstract
High-salinity wastewater discharged from offshore oil rigs (WORS) is harmful to marine environments. Therefore, WORS should be properly treated before discharge. In this study, a full-scale anaerobic baffle reactor (ABR) + sequencing batch reactor (SBR) + sand filter (SF) process was used for [...] Read more.
High-salinity wastewater discharged from offshore oil rigs (WORS) is harmful to marine environments. Therefore, WORS should be properly treated before discharge. In this study, a full-scale anaerobic baffle reactor (ABR) + sequencing batch reactor (SBR) + sand filter (SF) process was used for the first time to treat WORS at an inshore treatment terminal. After seeding with residual sludge from a municipal wastewater treatment facility, the start-up of the ABR and SBR was accomplished in one month. During a steady running period, the ABR + SBR process showed stable performance in treating WORS. The results of microbial diversity indicated that Rhizobiales, Thermotogales, and Actinomycetales were the most abundant genera in the ABR sample, while Acidobacteria DRC31, Lactobacillales, and Bacillales prevailed in the SBR sample. The results showed that ABR + SBR is a reliable process for WORS treatment, with the treated WORS meeting the National Sewage Comprehensive Emission Standards (GB8978-1996). Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Effect of Primary Variables on a Confined Plunging Liquid Jet Reactor
Author: Bader Al-Anzi <>
Affiliation: Environmental Technology Management and Department, College of Life Sciences, Kuwait University, Kuwait City, Kuwait
Abstract: The effects of the jet velocity, nozzle diameter, jet length and confining downcomer diameter and nozzle contraction angle on the gas/air entrainment rate, Qa, were investigated for a vertical confined plunging liquid jet reactor (CPLJR) as an alternative aeration process that is of interest in Kuwait and can be used in various applications, such as in wastewater treatment as an aerobic activated sludge process, fermentation and gas-liquid reactions. A CPLJR provides efficient oxygen transfer at a low cost. Various downcomer diameters (45–145 mm), jet lengths (200–500 mm), nozzle diameters (3.5–15 mm) and contraction angles (20–80°) were investigated. The air entrainment results showed that these were the primary parameters for the measured air entrainment rate in confined systems. The highest gas entrainment rates were achieved when the ratio of the downcomer diameter to the nozzle diameter was greater than approximately 5, as long as the liquid superficial velocity was sufficient to carry bubbles downward.
Keywords: contraction angle; gas/air entrainment rate; confined plunging jet; primary parameters; two phase"

Title: Basic dye removal with sorption onto low-cost natural textile fibers
Authors: George Z. Kyzas*, Evi Christodoulou, Dimitrios N. Bikiaris
Affiliation: Hephaestus Advanced Laboratory, Eastern Macedonia and Thrace Institute of Technology, Kavala, GR-65404, Greece

Title: SPSS Statistics Analysis of Circulating Water Quality Parameters under Variable-Frequency Vertical Electromagnetic Fields
Authors: Jianguo Wang and Fang He
Abstract: There is currently no unified electromagnetic anti-fouling mechanism. Most research focuses on the effect of structure parameters and water quality parameters on electromagnetic fields. The research on variations in water quality parameters under the influence of electromagnetic fields has not been reported. An experiment for variable-frequency vertical electromagnetic fields is proposed in this study. The relationship between conductivity, pH value, dissolved oxygen, turbidity, fouling resistance and magnetic acting time is carefully analyzed using SPSS statistical methods. Results show that magnetic acting time has a greater impact on conductivity than pH value and dissolved oxygen. Conductivity is used as an adaptive feedback control parameter for the optimum state of anti-fouling. The fouling resistance on the heat-exchanging surface of the magnetic experiment is smaller than that of the contrast experiment. Electromagnetic fields are applicable for mitigation of fouling. It is confirmed that physical water treatment is an effective and environment-friendly method to eliminate heat exchanger fouling. This research provides basic preparation for an
electromagnetic-adaptive closed-loop water treatmentdevice.

Title: Decomposition and decoloration of dyeing wastewater by ozone oxidation
Author: Dr. Hua Yin
Affiliation: Guangzhou institute of energy, Chinese academy of sciences;

Author: Zarook Shareefdeen
Affiliation: Chemical Eng, at American University of Sharjah;

Title: Degradation of Reactive Black 5 dye by graphene oxide supported manganese oxide
Authors: Hayarpi Saroyan, George Z. Kyzas <>, Anastasios I. Zouboulis, Eleni Deliyanni

Authors: Dr. Alfredo de Jesús Martínez Roldán <> or <>
Affiliation: Catedrático CONACYT - TecNM/ITD, Departamento de Ingenierías Química y Bioquímica, División de Estudios de Posgrado, Maestría en Sistemas Ambientales

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