Integrated electrochemical–biological treatment for efficient removal of metformin and its by-products: Optimization, mineralization, and toxicity assessment

Comparison of life cycle toxicity assessment methods for municipal wastewater treatment with the inclusion of direct emissions of metals, PPCPs and EDCs

Parabens (esters of p-hydroxybenzoic acid) are xenobiosis belonging to endocrine disruptors and commonly used as a preservative in cosmetics, food, pharmaceutical, and personal care products. Their wide use is leading to their appearance in water and wastewater in the range from ng/L to mg/L. In fact, the toxicity of benzylparaben is comparable to bisphenol A. Therefore, it is important to find not only effective but also ecofriendly methods for their removal from aqueous environment since the traditional wastewater treatment approaches are ineffective. Herein, for the first time, such extended comparison of several radical-driven technologies for paraben mixture degradation is presented. The detailed evaluation included (1) comparison of ozone and hydroxyl peroxide processes; (2) comparison of catalytic and photocatalytic processes (including photocatalytic ozonation); (3) characterisation of catalysts using SEM, XRD, DRS, XPS techniques and BET isotherm; (4) mineralisation, biodegradability and toxicity assessment; and (5) cost assessment. O3, H2O2/Fe2+, H2O2/UVC, O3/H2O2, O3/UVA, O3/H2O2/UVA, UVA/catalyst, O3/catalyst and O3/UVA/catalyst were selected from advanced oxidation processes to degrade parabens as well as to decrease its toxicity towards Aliivibrio fischeri, Corbicula fluminea and Lepidium sativum. Research was focused on the photocatalytic process involving visible light (UVA and natural sunlight) and TiO2 catalysts modified by different metals (Ag, Pt, Pd, Au). Photocatalytic oxidation showed the lowest efficiency, while in combining ozone with catalysis and photocatalysis process, degradation efficiency and toxicity removal were improved. Photocatalytic ozonation slightly improved degradation efficiency but appreciably decreased transferred ozone dose (TOD). Results indicate that the degradation pathway is different, or different transformation products (TPs) could be formed, despite that the hydroxyl radicals are the main oxidant.Graphical abstract

Parameters of the biotechnology of wastewater treatment for nitrogen and phosphorus removal using immobilized microorganisms are investigated. The acutest problem of municipal wastewater treatment is the low removal efficiency of biogenic compounds, namely nitrogen and phosphorus. Exceeding the discharge norms for nitrogen and phosphorus compounds leads to a dangerous ecological situation in water bodies of Ukraine. The intensity of transformation of nitrogen and phosphorus compounds is limited by the rather low growth rates of nitrifying bacteria (0.25–0.35 day -1 ), sensitivity to pH fluctuations (the value of 6.5–8 should be maintained), competitive relations with heterotrophs. It is advisable to use immobilized microorganisms to increase the concentration of nitrifying bacteria and create favorable conditions for biomass development. The perpendicular air flow in relation to wastewater flow in the aerobic bioreactor zone, which provides the oxidation capacity by ammonium nitrogen of up to 120–130 g/(m 3 ∙day), is investigated. It is established that the specific oxidation rate of organic matter in municipal wastewater treatment reaches 25 mg COD/(g/day), providing COD treatment efficiency of up to 90 %. The efficiency of wastewater treatment for ammonium nitrogen removal at an initial concentration of 30–50 mg/dm 3 is 97.3–99 %. The sequence of anaerobic-anoxic-anaerobic-aerobic processes, which provides the efficiency of wastewater treatment for removal of organic pollutants of 90–95 %, ammonium nitrogen 97–99 % and phosphates 93–95 %. with the treatment duration of up to 4 hours is studied.

Wastewater is major source of contaminants originating from the production, usage, and disposal of plastic materials. Due to their poor biodegradability of these contaminants in municipal wastewater treatment plants, additional advanced oxidation processes such as electrochemical treatments have been developed to improve the standard biological treatment. Here we review the applications of electrochemical treatments of wastewater for the removal of the following plastic contaminants: bisphenol A, phthalic acid esters, and benzotriazoles. We present the effectiveness of treatment in terms of contaminant removal and mineralization; the identification of transformation products; toxicity assessment; and process energy requirements. In the present review, we have focused on the applications of electrochemical treatments of wastewater for the removal of three important groups of contaminants originating mainly from plastics: bisphenol A, phthalic acid esters, and benzotriazoles. The review focuses on the research of electrochemical treatments for these contaminants from the last five years. The papers are assessed from the point of i) effectiveness of treatment in terms of contaminant removal and mineralization; ii) identification of transformation products; iii) toxicity assessment; iv) processes’ energy requirements. Electrochemical treatments were confirmed to be a viable option for the removal of selected contaminants from wastewater.

Biological treatment of Climbing Hempweed biomass through optimized composting technologies - Toxicity assessment and morphological study of Abelmoschus esculentus.

Exploring active and ecological materials for the restoration of complex pollution system is highly desired. This study presents a facile defect-tailoring strategy for combined pollutants purification with BiVO4 photocatalysis in which the jointed synchronous reaction of oxidation and reduction is integrated instead of the sequential reaction in two individual systems. XPS and EPR reveal that BiVO4 with a suitable oxygen vacancies (OVs) concentration and distribution exhibits superior photocatalytic activity under the coexistence of TC-HCl and Cr(VI) with Cr(VI) reduction efficiency increased by 71 times compared with the individual Cr(VI) system along with TC-HCl removal efficiency comparable to a single TC-HCl system. The mechanism of synchronous redox reactions mediated by surface OVs is revealed by comprehensive characterization together with reaction kinetic analysis, and the electronic band structure adjustment induced by the OVs variation is confirmed. Active species identification tests and intermediate product analysis confirm that singlet oxygen (1O2) accounts for the selective oxidation of TC-HCl, while electrons dominate the reduction of Cr(VI), under a coexistent environment. The influence of water quality parameters (e.g., pH, cations, anions, and organic substances) on the photocatalytic activity is investigated considering the complexity of the real aquatic environment. Importantly, toxicity assessment with Gram-negative strain E. coli as a model bacterium validates that the toxicity of the intermediates can be reduced to low or even ultralow levels. This work is dedicated to the mechanistic study of defect photocatalysis over BiVO4 and provides a jointed synchronous reaction system for combined pollutant purification.

Contamination of water resources by acetamiprid pesticide is considered one of the main environmental problems. The aim of this study was the optimization of acetamiprid removal from aqueous solutions by TiO2/Fe3O4/SiO2 nanocomposite using the response surface methodology (RSM) with toxicity assessment by Pseudomonas aeruginosa BCRC. To obtain the optimum condition for acetamiprid degradation using RSM and central composite design (CCD). The magnetic TiO2/Fe3O4/SiO2 nanocomposite was synthesized using co-precipitation and sol–gel methods. The surface morphology of the nanocomposite and magnetic properties of the as-synthesized Fe3O4 nanoparticles were characterised by scanning electron microscope and vibrating sample magnetometer, respectively. In this study, toxicity assessment tests have been carried out by determining the activity of dehydrogenase enzyme reducing Resazurin (RR) and colony forming unit (CFU) methods. According to CCD, quadratic optimal model with R2 = 0.99 was used. By analysis of variance, the most effective values of each factor were determined in each experiment. According to the results, the most optimal conditions for removal efficiency of acetamiprid (pH = 7.5, contact time = 65 min, and dose of nanoparticle 550 mg/L) was obtained at 76.55%. Effect concentration (EC50) for RR and CFU test were 1.950 and 2.050 mg/L, respectively. Based on the results obtained from the model, predicted response values showed high congruence with actual response values. And, the model was suitable for the experiment’s design conditions.

Efficient photocatalytic degradation of antibiotics using Z-scheme MIL-88(Fe)/Ti3C2/MoO3: Mechanistic insights and toxicity assessment.

The presence of arsenic and mercury in condensates causes several problems, including condensate quality, environmental pollution, health, and equipment integrity. According to a conventional cellulose-based filtration technique, it has limited lifetime and nonreusable. A metal filter is an alternative and promising approach according to their reusable potential and physic- and chemi-sorption processes. Thus, this work aimed to study the feasibility of using metal filter to remove arsenic and mercury contaminants in condensate. The removal efficiency of arsenic and mercury was investigated using two different material types and two morphological structures: copper and stainless-steel micromesh and foam with pore size 37-50 μm. Accordingly, the lab flow test built-in house was employed with a controlled retention time at 6 second. The removal efficiency was determined by monitoring the remaining arsenic and mercury content in the treated condensates compared to the initial concentrations in the fresh condensates by an atomic absorption spectrometer. Moreover, the regeneration processes of the used metal filter via heat and chemical treatment were also included in this study. The flow test result revealed that the stainless-steel foam exhibited highest arsenic and mercury removal efficiency with 69% and 80%, respectively. The best performance of arsenic and mercury removal in mesh structure showed on copper mesh with removal efficiency 50% and 28%, respectively. This implies that the morphological structure of the same material type also had a significant effect on the efficiency in mercury and arsenic removal apart from the type of material used. It was found that the foam structure has an improved removal efficiency for both arsenic and mercury decontaminations. Consequently, the foam structure was chosen for the further investigation on its reusability by the regenerative test, i.e., heat treatment for mercury removal and chemical treatment for arsenic removal. This indicates potential for further development to optimize its performance in effectively treating condensate with high mercury and arsenic concentrations. Furthermore, the utilization of metal filter offers an added safety benefit by mitigating the risk of hazardous mercury exposure to both operators and the surrounding environment. This study involves the first stage of research development on using metal-based substrates with micromesh and foam structure for decontamination of petroleum products. Cost effectiveness is one of our concerns which could make this study more realistic in operation. Possible removal mechanisms of arsenic and mercury including regenerative method of metal filter technology approach have been proposed.

This study was performed to determine the efficiency of the electro/persulfate process to remove basic violet 16 (BV16) dye and COD from aqueous solutions. The present study was experimentally performed on a laboratory scale. The effect of pH on the process was investigated independently, and after performing the experiments, the effect of voltage (volts), the dose of persulfate (g/L), initial concentration of BV16 dye, and electrolysis time was investigated with the model presented by Box Behnken design, and optimal conditions for BV16 dye removal was obtained. Under optimal conditions, COD removal efficiency and toxicity changes during the process were calculated, and the effect of distance between electrodes and surface of electrodes on process efficiency was investigated. By-products of oxidative degradation were determined with LS-MS. The amount of electrical energy consumed by the process was investigated by voltage changes and then the kinetics of the process was investigated by a pseudo-first-order model. The results showed that the electro/persulfate process in optimal conditions including pH of 5, a voltage of 11.43 V, persulfate dose of 0.09 g/L, initial BV16 concentration of 45 mg/L, and electrolysis time of 48.5 min could provide BV16 dye removal efficiency of 95% and COD removal efficiency of 57.14%. Findings of electrical energy consumption showed that with increasing voltage, the efficiency of the process increased, but the amount of energy consumption also increased. Under optimal conditions, increasing distance between the electrodes was led to a decrease in removal efficiency, but the removal efficiency increased with the increasing surface of the electrodes. Based on the kinetic results, the electro/persulfate process followed pseudo-first-order kinetics with R 2 = 0.9956. The present study showed that the electro/persulfate process as a useful technique has high efficiency in removing BV16 dye and its toxicity from aqueous solutions and can be effective and useful in removing the COD of solution.

Bioremediation of azo dye: A review on strategies, toxicity assessment, mechanisms, bottlenecks and prospects

Treatment of cooling tower blowdown water by using adsorption-electrocatalytic oxidation: Technical performance, toxicity assessment and economic evaluation

Enhancement of π–π aromatic interactions between hydrophobic Ionic Liquids and Methylene Blue for an optimum removal efficiency and assessment of toxicity by microbiological method

Manganese is naturally present in water, but its increased concentration in potable water is undesirable for multiple reasons. This study investigates an alternative method of demanganization by a newly synthesized TiO2-based adsorbent prepared through the transformation of titanyl sulphate monohydrate to amorphous sodium titanate. Its adsorption capacity for Mn2+ was determined, while a range of influential factors, such as the effect of contact time, adsorbent dosage, pH value, and added ions was evaluated. The adsorbent appeared highly effective for Mn2+ removal owing to its unique characteristics. Besides adsorption via electrostatic interactions, ion-exchange was also involved in the Mn2+ removal. Although the Mn2+ removal occurred within the whole investigated pH range of 4–8, the maximum was achieved at pH 7, with qe = 73.83 mg g-1. Equilibrium data revealed a good correlation with Langmuir isotherm in the absence of any ions or in the presence of monovalent co-existing ions, while the results in the presence of divalent co-existing ions showed a better fit to Freundlich isotherm. Additionally, the presence of monovalent cations (Na+, K+) only slightly decreased the Mn2+ removal efficiency as compared to divalent cations (Ca2+, Mg2+) that caused a greater decrease; however, the effect of anions (Cl-, SO4 2-) was insignificant. To provide insight into the adsorbent safety, the toxicity assessment was performed and showed no harmful effect on cell activity. Furthermore, the residual concentration of titanium after adsorption was always below the detection limit. The results imply that the synthesized TiO2-based adsorbent is a safe promising alternative method for demanganization. Highlights The synthesis of amorphous TiO2-based adsorbent was presented. The TiO2-based adsorbent was found to be efficient for Mn2+ removal. The Mn2+ removal mechanisms were adsorption and ion-exchange. Increasing pH enhanced the efficiency of Mn2+ removal. Divalent cations decreased the Mn2+ removal efficiency more than monovalent cations.

In this work, filamentous algae-based activated carbon was composited with Fe3O4 nanoparticles and applied as a potential adsorbent to remove Basic Blue 41. AAC/Fe3O4 nanocomposite was synthesised by the impregnation method and characterised by several techniques including, FTIR, FESEM, EDX, TGA, XRD, VSM, and BET. The characterisation results confirmed the existence of Fe3O4 in the nanocomposite structure, which had uniformly dispersed over AAC with mesoporous texture. The effects of various operational parameters on removal efficiency were investigated. The maximum AAC/Fe3O4 nanocomposite adsorption capacity (141 mg g−1) and removal rate (96.76%) were determined under optimum conditions (initial concentration of 100 mg L−1, solution pH of 9, nanocomposite dose = 1 g L−1 at 25°C for 90 min). The obtained adsorption data fitted well with the pseudo-second-order Langmuir isotherm model. The reusability assessment of AAC/Fe3O4 nanocomposite (with acidic solution) revealed about 11% decreases in the removal efficiency after five consecutive runs. Finally, bioassay studies using D. Magna confirmed AAC/Fe3O4 nanocomposite could create low toxicity and acceptable quality effluents. These attractive features make it a potential adsorbent for practical application in actual textile wastewater treatment.