Editorial

3 pages, 168 KiB

Open AccessEditorial

Wastewater Treatment: Current and Future Techniques

by Amin Mojiri and Mohammed J. K. Bashir

Water 2022, 14(3), 448; https://doi.org/10.3390/w14030448 - 01 Feb 2022

Cited by 21 | Viewed by 6648

With the rapid growth in urbanization and industrialization, environmental contamination has worsened due to the incessant discharge of toxic substances into water bodies, which has become a worldwide problem [...] Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

Research

Jump to: Editorial, Review

24 pages, 5817 KiB

Open AccessFeature PaperArticle

A New Polyvinylidene Fluoride Membrane Synthesized by Integrating of Powdered Activated Carbon for Treatment of Stabilized Leachate

by Salahaldin M. A. Abuabdou, Zeeshan Haider Jaffari, Choon-Aun Ng, Yeek-Chia Ho and Mohammed J. K. Bashir

Water 2021, 13(16), 2282; https://doi.org/10.3390/w13162282 - 20 Aug 2021

Cited by 8 | Viewed by 2386

Abstract

Stabilized landfill leachate contains a wide variety of highly concentrated non-biodegradable organics, which are extremely toxic to the environment. Though numerous techniques have been developed for leachate treatment, advanced membrane filtration is one of the most environmentally friendly methods to purify wastewater effectively. [...] Read more.

Stabilized landfill leachate contains a wide variety of highly concentrated non-biodegradable organics, which are extremely toxic to the environment. Though numerous techniques have been developed for leachate treatment, advanced membrane filtration is one of the most environmentally friendly methods to purify wastewater effectively. In the current study, a novel polymeric membrane was produced by integrating powdered activated carbon (PAC) on polyvinylidene fluoride (PVDF) to synthesize a thin membrane using the phase inversion method. The membrane design was optimized using response surface methodology (RSM). The fabricated membrane was effectively applied for the filtration of stabilized leachate using a cross-flow ring (CFR) test. The findings suggested that the filtration properties of fabricated membrane were effectively enhanced through the incorporation of PAC. The optimum removal efficiencies by the fabricated membrane (14.9 wt.% PVDF, 1.0 wt.% PAC) were 35.34, 48.71, and 22.00% for COD, colour and NH₃-N, respectively. Water flux and transmembrane pressure were also enhanced by the incorporated PAC and recorded 61.0 L/m²·h and 0.67 bar, respectively, under the conditions of the optimum removal efficiency. Moreover, the performance of fabricated membranes in terms of pollutant removal, pure water permeation, and different morphological characteristics were systematically analyzed. Despite the limited achievement, which might be improved by the addition of a hydrophilic additive, the study offers an efficient way to fabricate PVDF-PAC membrane and to optimize its treatability through the RSM tool. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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11 pages, 450 KiB

Open AccessArticle

Presence and Reduction of Anthropogenic Substances with UV Light and Oxidizing Disinfectants in Wastewater—A Case Study at Kuopio, Finland

by Jenni Ikonen, Ilpo Nuutinen, Marjo Niittynen, Anna-Maria Hokajärvi, Tarja Pitkänen, Eero Antikainen and Ilkka T. Miettinen

Water 2021, 13(3), 360; https://doi.org/10.3390/w13030360 - 30 Jan 2021

Cited by 6 | Viewed by 2950

Abstract

Anthropogenic substances are a major concern due to their potential harmful effects towards aquatic ecosystems. Because wastewater treatment plants (WWTPs) are not designed to remove these substances from wastewater, a part of the anthropogenic substances enter nature via WWTP discharges. During the spring [...] Read more.

Anthropogenic substances are a major concern due to their potential harmful effects towards aquatic ecosystems. Because wastewater treatment plants (WWTPs) are not designed to remove these substances from wastewater, a part of the anthropogenic substances enter nature via WWTP discharges. During the spring 2019, the occurrence of anthropogenic substances in the municipal wastewater effluent in Kuopio, Finland, was analysed. Furthermore, the capacity of selected disinfection methods to reduce these substances from wastewater was tested. The disinfection methods were ozonation (760 mL min⁻¹) with an OxTube hermetic dissolution method (1), the combined usage of peracetic acid (PAA) (<5 mg L⁻¹) and ultraviolet (UV) disinfection (12 mJ/cm²) (2), and the combined usage of hydrogen peroxide (H₂O₂) (<10 mg L⁻¹) and UV disinfection (12 mJ/cm²) (3). The substances found at the concentrations over 1 µg L⁻¹ in effluent (N = 3) were cetirizine (5.2 ± 1.3 µg L⁻¹), benzotriazole (BZT) (2.1 ± 0.98 µg L⁻¹), hydrochlorothiazide (1.7 ± 0.2 µg L⁻¹), furosemide (1.6 ± 0.2 µg L⁻¹), lamotrigine (1.5 ± 0.06 µg L⁻¹), diclofenac (DCF) (1.4 ± 0.2 µg L⁻¹), venlafaxine (1.0 ± 0.13 µg L⁻¹) and losartan (0.9 ± 0.2 µg L⁻¹). The reduction (%) with different methods (1, 2, 3) were: cetirizine (99.9, 5.0, NR = no removal), benzotriazole (67.9, NR, NR), hydrochlorothiazide (91.1, 5.9, NR), furosemide (99.7, 5.9, NR), lamotrigine (46.4, NR, 6.7), diclofenac (99.7, 7.1, 16.7), venlafaxine (91.3, NR, 1.1), losartan (99.6, 13.8, NR). Further research concerning the tested disinfection methods is needed in order to fully elucidate their potential for removing anthropogenic substances from purified wastewater. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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12 pages, 1860 KiB

Open AccessArticle

Selective Removal of Hexavalent Chromium from Wastewater by Rice Husk: Kinetic, Isotherm and Spectroscopic Investigation

by Usman Khalil, Muhammad Bilal Shakoor, Shafaqat Ali, Sajid Rashid Ahmad, Muhammad Rizwan, Abdulaziz Abdullah Alsahli and Mohammed Nasser Alyemeni

Water 2021, 13(3), 263; https://doi.org/10.3390/w13030263 - 22 Jan 2021

Cited by 36 | Viewed by 3452

Abstract

Chromium (Cr) in water bodies is considered as a major environmental issue around the world. In the present study, aqueous Cr(VI) adsorption onto rice husk was studied as a function of various environmental parameters. Equilibrium time was achieved in 2 h and maximum [...] Read more.

Chromium (Cr) in water bodies is considered as a major environmental issue around the world. In the present study, aqueous Cr(VI) adsorption onto rice husk was studied as a function of various environmental parameters. Equilibrium time was achieved in 2 h and maximum Cr(VI) adsorption was 78.6% at pH 5.2 and 120 mg L⁻¹ initial Cr(VI) concentration. In isotherm experiments, the maximum sorption was observed as 379.63 mg g⁻¹. Among four isotherm models, Dubinin–Radushkevich and Langmuir models showed the best fitting to the adsorption data, suggesting physical and monolayer adsorption to be the dominant mechanism. The kinetic modeling showed that a pseudo-second order model was suitable to describe kinetic equilibrium data, suggesting a fast adsorption rate of Cr(VI). The results of FTIR spectroscopy indicated that mainly –OH and C–H contributed to Cr(VI) adsorption onto rice husk. This paper provided evidence that rice husk could be a cost-effective, environment-friendly and efficient adsorptive material for Cr(VI) removal from wastewater due to its high adsorption capacity. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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13 pages, 4293 KiB

Open AccessArticle

Cometabolism of the Superphylum Patescibacteria with Anammox Bacteria in a Long-Term Freshwater Anammox Column Reactor

by Suguru Hosokawa, Kyohei Kuroda, Takashi Narihiro, Yoshiteru Aoi, Noriatsu Ozaki, Akiyoshi Ohashi and Tomonori Kindaichi

Water 2021, 13(2), 208; https://doi.org/10.3390/w13020208 - 16 Jan 2021

Cited by 54 | Viewed by 6854

Abstract

Although the anaerobic ammonium oxidation (anammox) process has attracted attention regarding its application in ammonia wastewater treatment based on its efficiency, the physiological characteristics of anammox bacteria remain unclear because of the lack of pure-culture representatives. The coexistence of heterotrophic bacteria has often [...] Read more.

Although the anaerobic ammonium oxidation (anammox) process has attracted attention regarding its application in ammonia wastewater treatment based on its efficiency, the physiological characteristics of anammox bacteria remain unclear because of the lack of pure-culture representatives. The coexistence of heterotrophic bacteria has often been observed in anammox reactors, even in those fed with synthetic inorganic nutrient medium. In this study, we recovered 37 draft genome bins from a long-term-operated anammox column reactor and predicted the metabolic pathway of coexisting bacteria, especially Patescibacteria (also known as Candidate phyla radiation). Genes related to the nitrogen cycle were not detected in Patescibacterial bins, whereas nitrite, nitrate, and nitrous oxide-related genes were identified in most of the other bacteria. The pathway predicted for Patescibacteria suggests the lack of nitrogen marker genes and its ability to utilize poly-N-acetylglucosamine produced by dominant anammox bacteria. Coexisting Patescibacteria may play an ecological role in providing lactate and formate to other coexisting bacteria, supporting growth in the anammox reactor. Patescibacteria-centric coexisting bacteria, which produce anammox substrates and scavenge organic compounds produced within the anammox reactor, might be essential for the anammox ecosystem. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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17 pages, 3318 KiB

Open AccessArticle

Removal of Polycyclic Aromatic Hydrocarbons (PAHs) from Produced Water by Ferrate (VI) Oxidation

by Tahir Haneef, Muhammad Raza Ul Mustafa, Khamaruzaman Wan Yusof, Mohamed Hasnain Isa, Mohammed J.K. Bashir, Mushtaq Ahmad and Muhammad Zafar

Water 2020, 12(11), 3132; https://doi.org/10.3390/w12113132 - 09 Nov 2020

Cited by 25 | Viewed by 3826

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are mutagenic and carcinogenic contaminants made up of fused benzene rings. Their presence has been reported in several wastewater streams, including produced water (PW), which is the wastewater obtained during oil and gas extraction from onshore or offshore installations. [...] Read more.

Polycyclic aromatic hydrocarbons (PAHs) are mutagenic and carcinogenic contaminants made up of fused benzene rings. Their presence has been reported in several wastewater streams, including produced water (PW), which is the wastewater obtained during oil and gas extraction from onshore or offshore installations. In this study, ferrate (VI) oxidation was used for the first time for the treatment of 15 PAHs, with the total concentration of 1249.11 μg/L in the produced water sample. The operating parameters viz., ferrate (VI) dosage, pH, and contact time were optimized for maximum removal of PAHs and chemical oxygen demand (COD). Central composite design (CCD) based on response surface methodology (RSM) was used for optimization and modeling to evaluate the optimal values of operating parameters. PAH and COD removal percentages were selected as the dependent variables. The study showed that 89.73% of PAHs and 73.41% of COD were removed from PW at the optimal conditions of independent variables, i.e., ferrate (VI) concentration (19.35 mg/L), pH (7.1), and contact time (68.34 min). The high values of the coefficient of determination (R²) for PAH (96.50%) and COD (98.05%) removals show the accuracy and the suitability of the models. The results showed that ferrate (VI) oxidation was an efficient treatment method for the successful removal of PAHs and COD from PW. The study also revealed that RSM is an effective tool for the optimization of operating variables, which could significantly help to reduce the time and cost of experimentation. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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14 pages, 2366 KiB

Open AccessEditor’s ChoiceArticle

Effective Adsorption of Reactive Black 5 onto Hybrid Hexadecylamine Impregnated Chitosan-Powdered Activated Carbon Beads

by Mohammadtaghi Vakili, Haider M. Zwain, Amin Mojiri, Wei Wang, Fatemeh Gholami, Zahra Gholami, Abdulmoseen S. Giwa, Baozhen Wang, Giovanni Cagnetta and Babak Salamatinia

Water 2020, 12(8), 2242; https://doi.org/10.3390/w12082242 - 09 Aug 2020

Cited by 26 | Viewed by 4011

Abstract

In this study, hexadecylamine (HDA) impregnated chitosan-powder activated carbon (Ct-PAC) composite beads were successfully prepared and applied to adsorption of the anionic dye reactive black 5 (RB5) in aqueous solution. The Ct-PAC-HDA beads synthesized with 0.2 g powdered activated carbon (PAC) and 0.04 [...] Read more.

In this study, hexadecylamine (HDA) impregnated chitosan-powder activated carbon (Ct-PAC) composite beads were successfully prepared and applied to adsorption of the anionic dye reactive black 5 (RB5) in aqueous solution. The Ct-PAC-HDA beads synthesized with 0.2 g powdered activated carbon (PAC) and 0.04 g HDA showed the highest dye removal efficiency. The prepared beads were characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Various adsorption parameters, i.e., adsorbent dosage, pH, and contact time, which affect the adsorption performance, were studied in a series of batch experiments. The obtained adsorption data were found to be better represented by Freundlich (R² = 0.994) and pseudo-second-order (R² = 0.994) models. Moreover, it was ascertained that the adsorption of RB5 onto Ct-PAC-HDA beads is pH-dependent, and the maximum Langmuir adsorption capacity (666.97 mg/g) was observed at pH 4. It was also proved that Ct-PAC-HDA beads were regenerable for repeated use in the adsorption process. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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Review

Jump to: Editorial, Research

16 pages, 2612 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Application of Natural Coagulants for Pharmaceutical Removal from Water and Wastewater: A Review

by Motasem Y. D. Alazaiza, Ahmed Albahnasawi, Gomaa A. M. Ali, Mohammed J. K. Bashir, Dia Eddin Nassani, Tahra Al Maskari, Salem S. Abu Amr and Mohammed Shadi S. Abujazar

Water 2022, 14(2), 140; https://doi.org/10.3390/w14020140 - 06 Jan 2022

Cited by 58 | Viewed by 16895

Abstract

Pharmaceutical contamination threatens both humans and the environment, and several technologies have been adapted for the removal of pharmaceuticals. The coagulation-flocculation process demonstrates a feasible solution for pharmaceutical removal. However, the chemical coagulation process has its drawbacks, such as excessive and toxic sludge [...] Read more.

Pharmaceutical contamination threatens both humans and the environment, and several technologies have been adapted for the removal of pharmaceuticals. The coagulation-flocculation process demonstrates a feasible solution for pharmaceutical removal. However, the chemical coagulation process has its drawbacks, such as excessive and toxic sludge production and high production cost. To overcome these shortcomings, the feasibility of natural-based coagulants, due to their biodegradability, safety, and availability, has been investigated by several researchers. This review presented the recent advances of using natural coagulants for pharmaceutical compound removal from aqueous solutions. The main mechanisms of natural coagulants for pharmaceutical removal from water and wastewater are charge neutralization and polymer bridges. Natural coagulants extracted from plants are more commonly investigated than those extracted from animals due to their affordability. Natural coagulants are competitive in terms of their performance and environmental sustainability. Developing a reliable extraction method is required, and therefore further investigation is essential to obtain a complete insight regarding the performance and the effect of environmental factors during pharmaceutical removal by natural coagulants. Finally, the indirect application of natural coagulants is an essential step for implementing green water and wastewater treatment technologies. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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20 pages, 2852 KiB

Open AccessReview

Multi-Integrated Systems for Treatment of Abattoir Wastewater: A Review

by Larryngeai Gutu, Moses Basitere, Theo Harding, David Ikumi, Mahomet Njoya and Chris Gaszynski

Water 2021, 13(18), 2462; https://doi.org/10.3390/w13182462 - 07 Sep 2021

Cited by 11 | Viewed by 4075

Abstract

Biological wastewater treatment processes such as activated sludge and anaerobic digestion remain the most favorable when compared to processes such as chemical precipitation and ion exchange due to their cost-effectiveness, eco-friendliness, ease of operation, and low maintenance. Since Abattoir Wastewater (AWW) is characterized [...] Read more.

Biological wastewater treatment processes such as activated sludge and anaerobic digestion remain the most favorable when compared to processes such as chemical precipitation and ion exchange due to their cost-effectiveness, eco-friendliness, ease of operation, and low maintenance. Since Abattoir Wastewater (AWW) is characterized as having high organic content, anaerobic digestion is slow and inadequate for complete removal of all nutrients and organic matter when required to produce a high-quality effluent that satisfies discharge standards. Multi-integrated systems can be designed in which additional stages are added before the anaerobic digester (pre-treatment), as well as after the digester (post-treatment) for nutrient recovery and pathogen removal. This can aid the water treatment plant effluent to meet the discharge regulations imposed by the legislator and allow the possibility for reuse on-site. This review aims to provide information on the principles of anaerobic digestion, aeration pre-treatment technology using enzymes and a hybrid membrane bioreactor, describing their various roles in AWW treatment. Simultaneous nitrification and denitrification are essential to add after anaerobic digestion for nutrient recovery utilizing a single step process. Nutrient recovery has become more favorable than nutrient removal in wastewater treatment because it consumes less energy, making the process cost-effective. In addition, recovered nutrients can be used to make nutrient-based fertilizers, reducing the effects of eutrophication and land degradation. The downflow expanded granular bed reactor is also compared to other high-rate anaerobic reactors, such as the up-flow anaerobic sludge blanket (UASB) and the expanded granular sludge bed reactor (EGSB). Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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27 pages, 1878 KiB

Open AccessEditor’s ChoiceReview

Recent Advances of Nanoremediation Technologies for Soil and Groundwater Remediation: A Review

by Motasem Y. D. Alazaiza, Ahmed Albahnasawi, Gomaa A. M. Ali, Mohammed J. K. Bashir, Nadim K. Copty, Salem S. Abu Amr, Mohammed F. M. Abushammala and Tahra Al Maskari

Water 2021, 13(16), 2186; https://doi.org/10.3390/w13162186 - 10 Aug 2021

Cited by 50 | Viewed by 8716

Abstract

Nanotechnology has been widely used in many fields including in soil and groundwater remediation. Nanoremediation has emerged as an effective, rapid, and efficient technology for soil and groundwater contaminated with petroleum pollutants and heavy metals. This review provides an overview of the application [...] Read more.

Nanotechnology has been widely used in many fields including in soil and groundwater remediation. Nanoremediation has emerged as an effective, rapid, and efficient technology for soil and groundwater contaminated with petroleum pollutants and heavy metals. This review provides an overview of the application of nanomaterials for environmental cleanup, such as soil and groundwater remediation. Four types of nanomaterials, namely nanoscale zero-valent iron (nZVI), carbon nanotubes (CNTs), and metallic and magnetic nanoparticles (MNPs), are presented and discussed. In addition, the potential environmental risks of the nanomaterial application in soil remediation are highlighted. Moreover, this review provides insight into the combination of nanoremediation with other remediation technologies. The study demonstrates that nZVI had been widely studied for high-efficiency environmental remediation due to its high reactivity and excellent contaminant immobilization capability. CNTs have received more attention for remediation of organic and inorganic contaminants because of their unique adsorption characteristics. Environmental remediations using metal and MNPs are also favorable due to their facile magnetic separation and unique metal-ion adsorption. The modified nZVI showed less toxicity towards soil bacteria than bare nZVI; thus, modifying or coating nZVI could reduce its ecotoxicity. The combination of nanoremediation with other remediation technology is shown to be a valuable soil remediation technique as the synergetic effects may increase the sustainability of the applied process towards green technology for soil remediation. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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19 pages, 1751 KiB

Open AccessReview

Treatment of Poultry Slaughterhouse Wastewater with Membrane Technologies: A Review

by Faryal Fatima, Hongbo Du and Raghava R. Kommalapati

Water 2021, 13(14), 1905; https://doi.org/10.3390/w13141905 - 09 Jul 2021

Cited by 34 | Viewed by 12324

Abstract

Poultry slaughterhouses produce a large amount of wastewater, which is usually treated by conventional methods. The traditional techniques face some challenges, especially the incapability of recovering valuable nutrients and reusing the treated water. Therefore, membrane technology has been widely adopted by researchers due [...] Read more.

Poultry slaughterhouses produce a large amount of wastewater, which is usually treated by conventional methods. The traditional techniques face some challenges, especially the incapability of recovering valuable nutrients and reusing the treated water. Therefore, membrane technology has been widely adopted by researchers due to its enormous advantages over conventional methods. Pressure-driven membranes, such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO), have been studied to purify poultry slaughterhouse wastewater (PSWW) as a standalone process or an integrated process with other procedures. Membrane technology showed excellent performance by providing high efficiency for pollutant removal and the recovery of water and valuable products. It may remove approximately all the pollutants from PSWW and purify the water to the required level for discharge to the environment and even reuse for industrial poultry processing purposes while being economically efficient. This article comprehensively reviews the treatment and reuse of PSWW with MF, UF, NF, and RO. Most valuable nutrients can be recovered by UF, and high-quality water for reuse in poultry processing can be produced by RO from PSWW. The incredible performance of membrane technology indicates that membrane technology is an alternative approach for treating PSWW. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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28 pages, 1097 KiB

Open AccessReview

An Overview of Per- and Polyfluoroalkyl Substances (PFAS) in the Environment: Source, Fate, Risk and Regulations

by Ziyad Abunada, Motasem Y. D. Alazaiza and Mohammed J. K. Bashir

Water 2020, 12(12), 3590; https://doi.org/10.3390/w12123590 - 21 Dec 2020

Cited by 97 | Viewed by 17414

Abstract

The current article reviews the state of art of the perfluoroalkyl and polyfluoroalkyl substances (PFASs) compounds and provides an overview of PFASs occurrence in the environment, wildlife, and humans. This study reviews the issues concerning PFASs exposure and potential risks generated with a [...] Read more.

The current article reviews the state of art of the perfluoroalkyl and polyfluoroalkyl substances (PFASs) compounds and provides an overview of PFASs occurrence in the environment, wildlife, and humans. This study reviews the issues concerning PFASs exposure and potential risks generated with a focus on PFAS occurrence and transformation in various media, discusses their physicochemical characterization and treatment technologies, before discussing the potential human exposure routes. The various toxicological impacts to human health are also discussed. The article pays particular attention to the complexity and challenging issue of regulating PFAS compounds due to the arising uncertainty and lack of epidemiological evidence encountered. The variation in PFAS regulatory values across the globe can be easily addressed due to the influence of multiple scientific, technical, and social factors. The varied toxicology and the insufficient definition of PFAS exposure rate are among the main factors contributing to this discrepancy. The lack of proven standard approaches for examining PFAS in surface water, groundwater, wastewater, or solids adds more technical complexity. Although it is agreed that PFASs pose potential health risks in various media, the link between the extent of PFAS exposure and the significance of PFAS risk remain among the evolving research areas. There is a growing need to address the correlation between the frequency and the likelihood of human exposure to PFAS and the possible health risks encountered. Although USEPA (United States Environmental Protection Agency) recommends the 70 ng/L lifetime health advisory in drinking water for both perfluorooctane sulfonate (PFO) perfluorooctanoic acid (PFOA), which is similar to the Australian regulations, the German Ministry of Health proposed a health-based guidance of maximum of 300 ng/L for the combination of PFOA and PFOS. Moreover, there are significant discrepancies among the US states where the water guideline levels for the different states ranged from 13 to 1000 ng L⁻¹ for PFOA and/or PFOS. The current review highlighted the significance of the future research required to fill in the knowledge gap in PFAS toxicology and to better understand this through real field data and long-term monitoring programs. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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31 pages, 1419 KiB

Open AccessReview

Insight on Extraction and Characterisation of Biopolymers as the Green Coagulants for Microalgae Harvesting

by Teik-Hun Ang, Kunlanan Kiatkittipong, Worapon Kiatkittipong, Siong-Chin Chua, Jun Wei Lim, Pau-Loke Show, Mohammed J. K. Bashir and Yeek-Chia Ho

Water 2020, 12(5), 1388; https://doi.org/10.3390/w12051388 - 14 May 2020

Cited by 45 | Viewed by 6379

Abstract

This review presents the extractions, characterisations, applications and economic analyses of natural coagulant in separating pollutants and microalgae from water medium, known as microalgae harvesting. The promising future of microalgae as a next-generation energy source is reviewed and the significant drawbacks of conventional [...] Read more.

This review presents the extractions, characterisations, applications and economic analyses of natural coagulant in separating pollutants and microalgae from water medium, known as microalgae harvesting. The promising future of microalgae as a next-generation energy source is reviewed and the significant drawbacks of conventional microalgae harvesting using alum are evaluated. The performances of natural coagulant in microalgae harvesting are studied and proven to exceed the alum. In addition, the details of each processing stage in the extraction of natural coagulant (plant, microbial and animal) are comprehensively discussed with justifications. This information could contribute to future exploration of novel natural coagulants by providing description of optimised extraction steps for a number of natural coagulants. Besides, the characterisations of natural coagulants have garnered a great deal of attention, and the strategies to enhance the flocculating activity based on their characteristics are discussed. Several important characterisations have been tabulated in this review such as physical aspects, including surface morphology and surface charges; chemical aspects, including molecular weight, functional group and elemental properties; and thermal stability parameters including thermogravimetry analysis and differential scanning calorimetry. Furthermore, various applications of natural coagulant in the industries other than microalgae harvesting are revealed. The cost analysis of natural coagulant application in mass harvesting of microalgae is allowed to evaluate its feasibility towards commercialisation in the industrial. Last, the potentially new natural coagulants, which are yet to be exploited and applied, are listed as the additional information for future study. Full article

(This article belongs to the Special Issue Wastewater Treatment: Current and Future Techniques)

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