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Toxics
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Advanced Technologies to Remove Toxic Compounds in Wastewater
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Advanced Technologies to Remove Toxic Compounds in Wastewater

A special issue of Toxics (ISSN 2305-6304). This special issue belongs to the section "Toxicity Reduction and Environmental Remediation".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 18701

Special Issue Editor

Prof. Dr. Conceptión Calvo

E-Mail Website
Guest Editor
Department of Microbiology, Institute of Water Research, University of Granada, Ramón y Cajal, 4, 18071 Granada, Spain
Interests: bioremediation; biofilm bioreactor; composting; biosurfactants; hydrocarbons; emerging pollutants
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Wastewater contains numerous pollutants that typically cannot be removed by conventional treatment methods. The entry of these wastewaters into the ecosystem causes serious damage as a result of the toxic effects of these compounds. This is intensified by the fact that continuous and prolonged discharges often take place, producing chronic toxicity. The toxicity of wastewater is due to the presence of both the macro-contaminants—namely the high content of dissolved organic matter or the nitrogen pollution—and micro-pollutants—such as heavy metals, micro and nano-plastics and emerging contaminants. The complex chemical composition of wastewater necessitates the implementation of combined and new technologies to achieve efficient removal of their toxicity and the development of a valuable toxicity assessment index. In particular, it should be noted that water from wastewater treatment plants is nowadays considered a sustainable water resource. The aim of this Special Issue is to provide updated and specialized information about the efficacy of advanced technologies which are valuable in the removal of wastewater toxicity to upgrade the efficiency of conventional wastewater treatments. It is hoped that this Special Issue will encourage the establishment of discussion forums to analyze in depth the importance of pollutants and optimal means of achieving high-quality water for reuse.

Prof. Dr. Conceptión Calvo
Guest Editor

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 submissions that pass pre-check are 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. Toxics 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 2600 CHF (Swiss Francs). 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

  • organic matter
  • nitrogen
  • emerging pollutants
  • heavy metals
  • micro and macro plastics
  • oxidative technologies
  • sorption technologies
  • bioreactor technologies
  • toxicity index

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Published Papers (6 papers)

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Research

13 pages, 5320 KiB  
Article
Combined Process of Biogenic Manganese Oxide and Manganese-Oxidizing Microalgae for Improved Diclofenac Removal Performance: Two Different Kinds of Synergistic Effects
by Quanfeng Wang, Cenhui Liao, Jujiao Zhao, Guoming Zeng, Wenbo Liu, Pei Gao, Da Sun and Juan Du
Toxics 2022, 10(5), 230; https://doi.org/10.3390/toxics10050230 - 30 Apr 2022
Cited by 3 | Viewed by 2222
Abstract
Biogenic manganese oxides (Bio-MnOx) have attracted considerable attention for removing pharmaceutical contaminants (PhCs) due to their high oxidation capacity and environmental friendliness. Mn-oxidizing microalgae (MnOMs) generate Bio-MnOx with low energy and organic nutrients input and degrade PhCs. The combined process of MnOMs and [...] Read more.
Biogenic manganese oxides (Bio-MnOx) have attracted considerable attention for removing pharmaceutical contaminants (PhCs) due to their high oxidation capacity and environmental friendliness. Mn-oxidizing microalgae (MnOMs) generate Bio-MnOx with low energy and organic nutrients input and degrade PhCs. The combined process of MnOMs and Bio-MnOx exhibits good prospects for PhCs removal. However, the synergistic effects of MnOMs and Bio-MnOx in PhCs removal are still unclear. The performance of MnOMs/Bio-MnOx towards diclofenac (DCF) removal was evaluated, and the mechanism was revealed. Our results showed that the Bio-MnOx produced by MnOMs were amorphous nanoparticles, and these MnOMs have a good Mn2+ tolerance and oxidation efficiency (80–90%) when the Mn2+ concentration is below 1.00 mmol/L. MnOMs/Bio-MnOx significantly promotes DCF (1 mg/L) removal rate between 0.167 ± 0.008 mg/L·d (by MnOMs alone) and 0.125 ± 0.024 mg/L·d (by Bio-MnOx alone) to 0.250 ± 0.016 mg/L·d. The superior performance of MnOMs/Bio-MnOx could be attributed to the continuous Bio-MnOx regeneration and the sharing of DCF degradation intermediates between Bio-MnOx and MnOMs. Additionally, the pathways of DCF degradation by Bio-MnOx and MnOMs were proposed. This work could shed light on the synergistic effects of MnOMs and Bio-MnOx in PhCs removal and guide the development of MnOMs/Bio-MnOx processes for removing DCF or other PhCs from wastewater. Full article
(This article belongs to the Special Issue Advanced Technologies to Remove Toxic Compounds in Wastewater)
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12 pages, 2260 KiB  
Article
Removal of Carbon Nanotubes from Aqueous Solutions by Sodium Hypochlorite: Effects of Treatment Conditions
by Mei Yang, Toshiya Okazaki and Minfang Zhang
Toxics 2021, 9(9), 223; https://doi.org/10.3390/toxics9090223 - 16 Sep 2021
Cited by 5 | Viewed by 2366
Abstract
The treatment of carbon nanotubes (CNTs) containing wastewater has become an important issue with increasing industrial application due to the risk CNTs may pose to the environment and human health. However, an effective method for treating wastewater containing CNTs has not been established. [...] Read more.
The treatment of carbon nanotubes (CNTs) containing wastewater has become an important issue with increasing industrial application due to the risk CNTs may pose to the environment and human health. However, an effective method for treating wastewater containing CNTs has not been established. Recently, we proposed a method to remove CNTs from aqueous dispersions using sodium hypochlorite (NaClO). To explore the practical applications of this method, we herein investigate the influence of different conditions, such as NaClO concentration, reaction temperature, pH value, and CNT concentration, on the CNT degradation rate. The results showed that the degradation of CNTs depends strongly on temperature and NaClO concentration: the higher the temperature and NaClO concentration, the faster the degradation rate. The optimal temperature and NaClO concentration are 50–70 °C and 2–3 wt%, respectively. Lower pH accelerated the degradation rate but induced the decomposition of NaClO. Furthermore, dispersants and other substances in the solution may also consume NaClO, thus affecting the degradation of CNTs. These findings are of significance for establishing a standard technique for CNT-containing industrial wastewater treatment, and for advancing the environmental sustainability of the CNT industry. Full article
(This article belongs to the Special Issue Advanced Technologies to Remove Toxic Compounds in Wastewater)
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16 pages, 16799 KiB  
Article
Design of Bio-Absorbent Systems for the Removal of Hydrocarbons from Industrial Wastewater: Pilot-Plant Scale
by Gloria Andrea Silva-Castro, Alfonso Rodríguez-Calvo, Tatiana Robledo-Mahón, Elisabet Aranda, Jesús González-López and Concepción Calvo
Toxics 2021, 9(7), 162; https://doi.org/10.3390/toxics9070162 - 7 Jul 2021
Cited by 1 | Viewed by 2640
Abstract
The objective of this study was the development and design of a treatment system at a pilot-plant scale for the remediation of hydrocarbons in industrial wastewater. The treatment consists of a combined approach of absorption and biodegradation to obtain treated water with sufficient [...] Read more.
The objective of this study was the development and design of a treatment system at a pilot-plant scale for the remediation of hydrocarbons in industrial wastewater. The treatment consists of a combined approach of absorption and biodegradation to obtain treated water with sufficient quality to be reused in fire defense systems (FDSs). The plant consists of four vertical flow columns (bioreactors) made of stainless steel (ATEX Standard) with dimensions of 1.65 × 0.5 m and water volumes of 192.4 L. Each bioreactor includes a holder to contain the absorbent material (Pad Sentec polypropylene). The effectiveness of the treatment system has been studied in wastewater with high and low pollutant loads (concentrations higher than 60,000 mg L−1 of total petroleum hydrocarbons (TPH) and lower than 500 mg L−1 of TPHs, respectively). The pilot-plant design can function at two different flow rates, Q1 (180 L h−1) and Q2 (780 L h−1), with or without additional aeration. The results obtained for strongly polluted wastewaters showed that, at low flow rates, additional aeration enhanced hydrocarbon removal, while aeration was unnecessary at high flow rates. For wastewater with a low pollutant load, we selected a flow rate of 780 L h−1 without aeration. Different recirculation times were also tested along with the application of a post-treatment lasting 7 days inside the bioreactor without recirculation. The microbial diversity studies showed similar populations of bacteria and fungi in the inlet and outlet wastewater. Likewise, high similarity indices were observed between the adhered and suspended biomass within the bioreactors. The results showed that the setup and optimization of the reactor represent a step forward in the application of bioremediation processes at an industrial/large scale. Full article
(This article belongs to the Special Issue Advanced Technologies to Remove Toxic Compounds in Wastewater)
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15 pages, 1018 KiB  
Article
Evaluation of the Potential of Sewage Sludge Mycobiome to Degrade High Diclofenac and Bisphenol-A Concentrations
by Ulises Conejo-Saucedo, Alejandro Ledezma-Villanueva, Gabriela Ángeles de Paz, Mario Herrero-Cervera, Concepción Calvo and Elisabet Aranda
Toxics 2021, 9(6), 115; https://doi.org/10.3390/toxics9060115 - 23 May 2021
Cited by 13 | Viewed by 3561
Abstract
One of the most challenging environmental threats of the last two decades is the effects of emerging pollutants (EPs) such as pharmaceutical compounds or industrial additives. Diclofenac and bisphenol A have regularly been found in wastewater treatment plants, and in soils and water [...] Read more.
One of the most challenging environmental threats of the last two decades is the effects of emerging pollutants (EPs) such as pharmaceutical compounds or industrial additives. Diclofenac and bisphenol A have regularly been found in wastewater treatment plants, and in soils and water bodies because of their extensive usage and their recalcitrant nature. Due to the fact of this adversity, fungal communities play an important role in being able to safely degrade EPs. In this work, we obtained a sewage sludge sample to study both the culturable and non-culturable microorganisms through DNA extraction and massive sequencing using Illumina MiSeq techniques, with the goal of finding degraders adapted to polluted environments. Afterward, degradation experiments on diclofenac and bisphenol A were performed with the best fungal degraders. The analysis of bacterial diversity showed that Dethiosulfovibrionaceae, Comamonadaceae, and Isosphaeraceae were the most abundant families. A predominance of Ascomycota fungi in the culturable and non-culturable population was also detected. Species such as Talaromyces gossypii, Syncephalastrum monosporum, Aspergillus tabacinus, and Talaromyces verruculosus had remarkable degradation rates, up to 80% of diclofenac and bisphenol A was fully degraded. These results highlight the importance of characterizing autochthonous microorganisms and the possibility of selecting native fungal microorganisms to develop tailored biotransformation technologies for EPs. Full article
(This article belongs to the Special Issue Advanced Technologies to Remove Toxic Compounds in Wastewater)
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20 pages, 3311 KiB  
Article
Total and Metabolically Active Microbial Community of Aerobic Granular Sludge Systems Operated in Sequential Batch Reactors: Effect of Pharmaceutical Compounds
by Barbara Muñoz-Palazon, Aurora Rosa-Masegosa, Miguel Hurtado-Martinez, Alejandro Rodriguez-Sanchez, Alexander Link, Ramiro Vilchez-Vargas, Alejandro Gonzalez-Martinez and Jesus Gonzalez Lopez
Toxics 2021, 9(5), 93; https://doi.org/10.3390/toxics9050093 - 23 Apr 2021
Cited by 12 | Viewed by 2784
Abstract
Two aerobic granular sludge (AGS) sequential batch reactors were operated at a mild (15 °C) temperature for 180 days. One of those bioreactors was exposed to a mixture of diclofenac, naproxen, trimethoprim, and carbamazepine. The AGS system, operating under pressure from emerging contaminants, [...] Read more.
Two aerobic granular sludge (AGS) sequential batch reactors were operated at a mild (15 °C) temperature for 180 days. One of those bioreactors was exposed to a mixture of diclofenac, naproxen, trimethoprim, and carbamazepine. The AGS system, operating under pressure from emerging contaminants, showed a decrease in COD, BOD5, and TN removal capacity, mainly observed during the first 100 days, in comparison with the removal ratios detected in the control bioreactor. After an acclimatisation period, the removal reached high-quality effluent for COD and TN, close to 95% and 90%, respectively. In the steady-state period, trimethoprim and diclofenac were successfully removed with values around 50%, while carbamazepine and naproxen were more recalcitrant. The dominant bacterial OTUs were affected by the presence of a mixture of pharmaceutical compounds, under which the dominant phylotypes changed to OTUs classified among the Pseudomonas, Gemmobacter, and Comamonadaceae. The RT-qPCR and qPCR results showed the deep effects of pharmaceutical compounds on the number of copies of target genes. Statistical analyses allowed for linking the total and active microbial communities with the physico-chemical performance, describing the effects of pharmaceutical compounds in pollution degradation, as well as the successful adaptation of the system to treat wastewater in the presence of toxic compounds. Full article
(This article belongs to the Special Issue Advanced Technologies to Remove Toxic Compounds in Wastewater)
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15 pages, 32164 KiB  
Article
Removal of Antibiotics and Nutrients by Vetiver Grass (Chrysopogon zizanioides) from a Plug Flow Reactor Based Constructed Wetland Model
by Saumik Panja, Dibyendu Sarkar, Zhiming Zhang and Rupali Datta
Toxics 2021, 9(4), 84; https://doi.org/10.3390/toxics9040084 - 15 Apr 2021
Cited by 21 | Viewed by 3818
Abstract
Overuse of antibiotics has resulted in widespread contamination of the environment and triggered antibiotic resistance in pathogenic bacteria. Conventional wastewater treatment plants (WWTPs) are not equipped to remove antibiotics. Effluents from WWTPs are usually the primary source of antibiotics in aquatic environments. There [...] Read more.
Overuse of antibiotics has resulted in widespread contamination of the environment and triggered antibiotic resistance in pathogenic bacteria. Conventional wastewater treatment plants (WWTPs) are not equipped to remove antibiotics. Effluents from WWTPs are usually the primary source of antibiotics in aquatic environments. There is an urgent need for cost-effective, environment-friendly technologies to address this issue. Along with antibiotics, nutrients (nitrogen and phosphorus) are also present in conventional WWTP effluents at high concentrations, causing environmental problems like eutrophication. In this study, we tested vetiver grass in a plug flow reactor-based constructed wetland model in a greenhouse setup for removing antibiotics ciprofloxacin (CIP) and tetracycline (TTC), and nutrients, N and P, from secondary wastewater effluent. The constructed wetland was designed based on a previous batch reaction kinetics study and reached a steady-state in 7 days. The measured concentrations of antibiotics were generally consistent with the modeling predictions using first-order reaction kinetics. Vetiver grass significantly (p < 0.05) removed 93% and 97% of CIP and TTC (initial concentrations of 10 mg/L), simultaneously with 93% and 84% nitrogen and phosphorus, respectively. Results show that using vetiver grass in constructed wetlands could be a viable green technology for the removal of antibiotics and nutrients from wastewater. Full article
(This article belongs to the Special Issue Advanced Technologies to Remove Toxic Compounds in Wastewater)
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