Wastewater Removal Research Articles

Sustainable mainstream deammonification by ion exchange and bioregeneration via partial nitritation/anammox

The partial nitritation and anammox (PN/A) process has gained popularity for the treatment of nitrogen removal in wastewater due to significant energy savings and its potentially much lower CO2 footprint. However, the treatment of mainstream municipal wastewater by PN/A has been limited mainly due to its unsuitable composition. In this research, we apply ion exchange using a zeolite column to selectively remove and concentrate ammonium from mainstream municipal wastewater. After an absorption phase, the ion exchange column is regenerated using a brine solution. The ammonium rich brine is “bioregenerated” in a PN/A reactor where ammonium is converted to nitrogen gas allowing the brine to be reused in another cycle of ion exchange regeneration. To successfully remove ammonium from the spent brine, anammox and ammonia oxidizing bacteria (AOB) were first cultivated in separate reactors under hypersaline conditions (4.0 %) and later combined in a single PN/A reactor. After continuous operation with sea water, the PN/A reactor treated recirculating brine from the ion exchange column for 48 cycles of ammonium absorption and bioregeneration with minimal blowdown. The various cations of the regenerant solution were stable except for calcium that reached very high values upwards of 3000 mg/L as Ca2+ and finally caused PN/A reactor failure due to mineral precipitation. The buildup of high concentrations of calcium in the regenerant was addressed in two ways: 1) 20 % regenerant replacement per cycle, and 2) precipitation of CaCO3 via the addition of sodium carbonate. Both methods were applied to 30 absorption and bioregeneration cycles each and shown to be effective in keeping calcium concentrations from accumulating in the regenerant allowing for stable PN/A reactor operation.

Polyvinyl Alcohol-Citric Acid: A New Material for Green and Efficient Removal of Cationic Dye Wastewater.

The citric acid (CA) cross-linked polyvinyl alcohol (PVA) adsorbent, PVA-CA, was efficiently synthesized and its application to the removal of dyes in water, particularly the cationic dye, methylene blue (MB), was thoroughly investigated. The morphologies and physiochemical characteristics of PVA-CA were fully characterized by SEM, FT-IR, XRD, TGA, BET, and XPS. The effects of contact time, adsorbent dosage, MB concentration, solution pH, and temperature on the adsorption performance were compared using controllable methods. The maximum adsorption capacity of PVA-CA was 709.86 mg g-1 and the removal rate remained high through several adsorption-desorption cycles, demonstrating that such a composite absorbent has a good adsorption performance and recoverability. Further analysis by the density functional theory (DFT) showed that van der Waals interactions, electrostatic interactions and hydrogen bonding interactions between PVA-CA and MB played significant roles in the adsorption mechanism.

Valorization of waste gypsum board as a green adsorbent for efficient fluoride removal in groundwater and wastewater treatment

The escalating generation of construction waste during building reconstruction and remodeling underscores the significance of recycling for environmental preservation and resource conservation. In this context, we propose the valorization of waste gypsum board (WGB), a common construction waste material, as a value-added environmental purification agent. WGB, composed primarily of CaSO4, displays the potential to react with fluoride to form CaF2, making it a promising adsorbent for fluoride removal. Through density functional theory analysis, we determined that WGB possesses mesoporous characteristics, with pore sizes ranging from 1 to 20 nm. While thermal treatment has been effective in enhancing fluoride adsorption on other adsorbents, our investigations revealed that the crystalline structure (CaSO4) of WGB remained unchanged under thermal treatment, limiting its impact on the fluoride adsorption capacity. Nevertheless, WGB exhibited a remarkably high fluoride adsorption capacity (285.90 mg/g), surpassing those of other reported adsorbents. Furthermore, the WGB demonstrated excellent fluoride removal performance, even at higher solution pH levels. In artificial wastewater, a dose of 3.33 g/L WGB achieved a remarkable removal efficiency (> 95%). The applicability of WGB was validated by successful fluoride removal in real wastewater and groundwater, with 94% of fluoride in groundwater removed using 0.33 g/L of WGB and 97% of the fluoride in the wastewater removed with 1.67 g/L WGB. This study opens a promising pathway, demonstrating the potential of WGB as a green adsorbent for the effective treatment of fluorine-contaminated wastewater and groundwater, transcending its traditional role in waste recycling.

Synthesis and fabrication of segregative and durable MnO2@chitosan composite aerogel beads for uranium(VI) removal from wastewater

To address the imperative need for efficient removal of uranium-containing wastewater and mitigate radioactive contamination risks associated with nuclear energy, the development of materials with high removal efficiency and facile separation is crucial. This study designed and synthesised MnO2@chitosan (CTS) composite aerogel beads by in-situ growing δ-MnO2 on porous CTS aerogel beads. This approach not only mitigates the agglomeration of MnO2 nanospheres but also significantly enhances the porous structure and surface area of MnO2@CTS. These cost-effective and eco-friendly millimeter-scale spherical aerogels exhibited convenient separation properties after adsorption. These characteristics help mitigate the risk of equipment seam blockage and secondary pollution that are often associated with powdered adsorbents. Additionally, MnO2@CTS exhibited remarkable mechanical strength (stress approximately 0.55 MPa at 60 % strain), enabling rapid separation and easy regeneration while maintaining high adsorption performance even after five cycles. Significantly, MnO2@CTS exhibited a maximum adsorption capacity of 410.7 mg/g at pH 6 and 298 K, surpassing reported values for most CTS/MnO2-based adsorbents. The chemisorption process of U(VI) on MnO2@CTS followed the pseudo-second-order kinetic and Dubinin-Radushkevish models. X-ray photoelectron spectroscopy analysis further confirmed the reduction of U(VI) to U(V/IV). These findings highlight the substantial potential of MnO2@CTS aerogel beads for U(VI) removal from aqueous solutions, positioning them as a promising solution for addressing U(VI) contamination in wastewater.

Effective catalysts for wastewater treatment under sunlight: Gas dependent preparation of mesoporous biphasic N-doped TiO2 nanoparticles

Photocatalysts are playing an indispensable role in tackling environmental and energy crises; however, they are associated with poor solar energy utilization. In this study, N-doped titanium dioxide (N-TiO2) nanocrystals were successfully prepared using benign N-source, guanidine chloride by simple sol-gel technique. The significance of annealing gases environment (air, argon, and nitrogen) on their physicochemical properties and photocatalytic activity under direct sunlight irradiation was investigated. XRD and Raman data revealed that the crystal structure of spheroidal N-TiO2 nanocrystals was transformed from monophase anatase with less crystallinity in argon, and nitrogen to dual-phase anatase/rutile (A/R) with higher crystallinity in air. Importantly, XPS confirmed the successful incorporation of N in interstitial sites of the bare titania structure. Moreover, DRS and PL results revealed that the introduction of N into the TiO2 matrix not only led to a red shift towards visible-light but also lowered the bandgap energy (2.35 eV) and suppressed charge carriers recombination. BET showed a typical IV isotherm of mesoporous N-TiO2 nanomaterials with a high specific surface area in the range of 80–103 m2 g−1. Furthermore, their rhodamine B (RhB) photodegradation performance and thermal-stability were dictated by the annealing gas type. Nobly, the N-TiO2 prepared in air demonstrated the highest degradation performance (99%) with the fastest rate (0.0158 min−1) which is twice faster as the control TiO2 material. Its real textile wastewater removal was 63% and 56.5% COD and TOC, respectively. These improved performances are mainly attributed to its higher crystallinity, A/R mixed phase, aqueous-dispersion character, and lower recombination rate. Such gas driven-synthesis of photocatalysts has practical applications in designing other solar energy conversion systems.

Use of Lactobacillus Bacteria to Degrade Oil and Grease in Restaurant Wastewater

Restaurant wastewater poses a significant environmental challenge, especially concerning the removal of oil and grease, which is known to be highly persistent. To tackle this issue, the research utilized a Lactobacillus bacteria consortium to effectively degrade oil and grease present in the wastewater. The Lactobacillus bacteria consortium was applied in an aerobic environment within the Grease Trap, while various treatment conditions, such as hydraulic retention time (HRT) and aeration rate, were evaluated to determine the optimal settings for the SBR. By employing this combined pre-treatment and SBR approach, distinct aerobic and anaerobic conditions were created, leading to significant removal of pollutant parameters by microorganisms. Remarkably, the study's findings demonstrated that at a 24-hour retention time and a 14 L/minute aeration rate, the Lactobacillus bacteria consortium achieved an impressive 97.42% removal of oil and grease, compared to only 84.54% removal by the Grease Trap without bacteria. The pretreatment of the Lactobacillus bacteria consortium led to even higher reductions in other pollutant parameters. By harnessing the power of the Lactobacillus bacteria consortium and employing the SBR in combination with pre-treatment, this approach holds great potential for addressing the persistent challenge of oil and grease removal in restaurant wastewater and improving overall water quality.

Nitrification of an anaerobic filter effluent in a flat sheet membrane aerated biofilm reactor

Compared with activated sludge intensification by integrating membrane aerated biofilm reactors (MABRs) to promote sustainable nitrogen removal, treatment of anaerobic reactors effluents with MABRs is scarcely studied. Here the capability of a flat sheet MABR for nitrogen removal and nitrification of real wastewater previously treated in an anaerobic filter was analyzed. Removal of 71–81 % of ammonia with 54–72 % conversion to nitrate, while eliminating 13–28 % of total inorganic nitrogen in water containing 38–80 mg ammonia-N/L and 25–78 mg COD/L was achieved with aeration at atmospheric pressure. Experimental data in combination with stoichiometry and sequencing suggested a combination of autotrophic and heterotrophic bacteria associated to the nitrogen cycle was present in the biofilm. Nitrogen and ammonia removal rates up to 117 mg N/L-d and 258 mg N/L-d, respectively evidenced a competitive nitrogen conversion capability of the flat sheet MABR attained with non-pressurized aeration involving potential energy savings. Effluent content (mg/L) of ammonia 10–17, nitrite 13–23, nitrate 21–37 and phosphate 21–45, is suitable for further nitrogen removal or nutrient recovery as dissolved fertilizer for irrigation.

Turbidity reduction efficacies of seed kernels of Mango (Mangifera indica) genotypes in Uganda

Alum and ferric salts as traditional chemical coagulants for turbidity removal in water and wastewater are expensive, and have known harmful effects. Thus, attempts to replace the chemical coagulants with safe and effective natural solutions are increasingly being made in terms of research studies to investigate the coagulation efficacies of various plants one of which is Mango (Mangifera indica). It is worth noting that M. indica has various genotypes of different origins across the world. In this study, eight (8) common M. indica genotypes in Uganda were identified, protein contents of their seed kernels determined, and coagulating efficacies investigated. Coagulation solution of each selected genotype was obtained by dissolving 5 g powder of the selected Mango seed kernel sample in 100 mL of distilled water. Next, 5 mL of this coagulant (or stock) solution was used to treat 200 mL of turbid water with turbidity ranging from 15 to 120 NTU. Using 0.01 M hydrochloric acid as an extraction solvent, protein contents of selected genotypes including Apple mango, Kate, Kent, Bire, Doodo red, Takataka, Kagoogwa, and Tommy Atkins were 38.02 %, 30.66 %, 15.94 %, 22.11 %, 21.50 %, 16.98 %, 16.36 %, and 17.87 %, respectively. Efficacies of coagulant from Apple mango, Kate, Kent, Bire, Doodo red, Takataka, Kagoogwa, and Tommy Atkins seed kernel samples were 92.2, 89.3, 66.0, 78.7, 76.9, 71.1, 68.9, and 73.1 %, respectively. Apple mango was the best performing genotype as a coagulant and this was followed by Kate. Coagulation efficacy was generally found to increase with increasing turbidity and/or coagulant's concentration. For instance, Apple Mango coagulant removed 16.7 %, 50.3 %, and 92.2 % of initial turbidity 15, 65 and 120 NTU, respectively. Kent removed 57.5, 66, and 69 % of initial turbidity 120 NTU using 5, 20, and 30 mL of stock solution, respectively. This study demonstrated the influence of the choice of a plant genotype on coagulation efficacy.

Kinetic modelling for COD and nitrate-N removal from hatchery wastewater through biological approach

This study was conducted to determine the nutrient removal efficiency via the application of mixed cultures from the synthetic hatchery wastewater based on the first-order, second-order and Stover Kincannon models. The synthetic wastewater was prepared according to the characterization of the collected hatchery wastewater sample, and the collected mixed cultures from the pond sediment were acclimatized accordingly. The samples were tested for chemical oxygen demand (COD) and nitrate-N concentration using a Hach spectrophotometer to determine the removal value of the nutrients. The findings show that the highest removal percentage for COD was up to 31.35% on day 3. Meanwhile, the highest removal percentage for nitrate-N was obtained on day 4 at 43.48%. The obtained correlation coefficient, for COD through first-order, second-order, and Stover Kincannon models is 1, 0.6774, and 0.965, respectively, suggesting that the kinetics of COD removal can be described most properly by the first-order model. A similar model was also reported for nitrate-N with value of 1, 0.7563, and 0.8693 for the first-order, second-order, and Stover Kincannon models, respectively. Based on the findings, the acclimatized mixed culture used in this study could be a potent natural COD and nitrate-N removal in the hatchery wastewater.

Efficient heterotrophic nitrification by a novel bacterium Sneathiella aquimaris 216LB-ZA1-12T isolated from aquaculture seawater

High concentration of ammonia poses a common threat to the healthy breeding of marine aquaculture organisms. Since aquaculture water is rich in organic matter, heterotrophic nitrifying bacteria might play a crucial role in ammonia removal. However, their roles in ammonia oxidation remain unknown. Here, we report a novel strain isolated from shrimp aquaculture seawater, identified as Sneathiella aquimaris 216LB-ZA1–12T, capable of heterotrophic nitrification. It is the first characterized heterotrophic nitrifier of the order Sneathiellales in the class Alphaproteobacteria. It exhibits high activity in heterotrophic nitrification, removing nearly 94% of ammonium-N under carbon-constrained conditions in 8 days with no observed nitrite accumulation. The heterotrophic nitrification pathway, inferred based on detection and genomic data was as follows: NH4+→NH2OH→NO→NO2-→NO3-. While this pathway aligns with the classical nitrification pathway, while the significant difference lies in the absence of classical HAO and HOX encoding genes in the genome, which is common in heterotrophic nitrifying bacteria. In summary, this bacterium is not only valuable for studying the nitrifying mechanism, but also holds potential for practical applications in ammonia removal in marine aquaculture systems and saline wastewater.

LED-irradiated photo-Fenton process on pollutant removal: outcomes, trends, and limitations.

This manuscript critically reviews the state of the art on the application of photo-Fenton processes irradiated by light-emitting diode arrays (LED) with a focus on the removal of contaminants of emerging concern (CEC) from aqueous matrices. LEDs are clean, low-cost radiation sources with longer lifespan compared to mercury lamps. This study covers the influence of LED sources, wavelengths, and dose upon CEC removal, and the potential for disinfection, abatement of antibiotic-resistant bacteria (ARB), and genes (ARG). The bibliographic search was performed in Scopus database using keyword combinations and resulted in a portfolio containing 52 relevant articles published between 2010-2023. According to reviewed papers, LED photoreactor design has evolved in the past decade aiming to improve CEC degradation in aqueous matrices while reducing construction and operation costs, and energy consumption. Among several reactors (annular, fluidized bed, parallel plate, wireless, pathway systems, and microreactor) surveyed for their performance and scalability, LED chips and strips are particularly suitable for application due to their wide emission angle (≈120°) and small size (mm2), which allow for, respectively, efficient illumination coverage and flexible arrangement and design. LED microreactors are very efficient in the degradation of contaminants and scalable with reduced area requirements. Although most studies were performed in synthetic solutions and at laboratory scale, the externally LED irradiated cylindrical reactor was successful for application in full-scale municipal water treatment plants. Future studies should focus on evaluating CEC removal in wastewater using scalable devices for continuous operation of solar photo-Fenton at night.

Cellulose Acetate/Polyethylene Glycol Composite Beads for Efficient Removal of Methylene Blue

The development of eco-friendly and biodegradable adsorbent with excellent adsorption performance is of great importance for the efficient dye removal in wastewater. Herein, an efficient and biodegradable composite adsorbent bead was fabricated from cellulose acetate (CA) modified with low molecular weight polyethylene glycol 200 (PEG200) for the adsorptive removal of methylene blue dye (MB) from aqueous solution. The weight fraction of PEG was varied to investigate the effect of material bead composition on the morphology, molecular structure, crystal phases, thermal stability, mechanical properties, and adsorption performance of the composite beads. Batch adsorption was carried out at various times to estimate the time at equilibrium adsorption capacity and kinetic model. Various operating conditions such as pH, initial MB concentration, and adsorbent dosage in experiment were also executed to examine the adsorption performance of this system. The result showed that all beads have porous structure and the pore size increase after the addition of PEG200. The adsorption capacity and % MB removal generally showed an improvement with the rise of PEG content. The batch adsorption experiments demonstrated that the best % removal and adsorption capacity of MB were 93.35 % and 28.005 mg/g, respectively, that was obtained by composite CA/PEG200 (80/20) bead at pH of 11, initial MB concentration of 30 mg/L, and bead dosage of 1 g/L. The adsorption kinetic fitted well to Elovich-kinetic model with average R2 of 0.844. Overall, this work offers new finding into the development of effective, environmentally friendly, and inexpensive cellulose-based adsorbents for wastewater remediation.

Poloxamer 407 Combined with Polyvinylpyrrolidone To Prepare a High-Performance Poly(ether sulfone) Ultrafiltration Membrane.

At present, the design and fabrication of polymer membranes with high permeability and good retention ability are still huge challenges. In this study, the commercial Poloxamer 407 (Pluronic F127) is selected as a multifunctional additive, and polyvinylpyrrolidone is used as a pore-forming agent to modify the poly(ether sulfone) membrane by liquid-liquid phase conversion technology to prepare an ultrafiltration membrane with excellent performance. The hydrophobic poly(propylene oxide) segment in Poloxamer 407 guarantees that this copolymer can be firmly anchored to the poly(ether sulfone) matrix, and the hydrophilic poly(ethylene oxide) segments in Poloxamer 407 impart a stronger hydrophilic nature to the modified membrane surface. Therefore, the permeability and hydrophilicity of the modified membrane are significantly improved and the modified membrane also has good stability. When the amount of Poloxamer 407 added to the casting solution reached 0.6 g, the water flux of the modified membrane was as high as 368 L m-2 h-1, and the rejection rate of bovine serum albumin was close to 98%. In the test to isolate organic small molecule dyes, the retention rate of the modified membrane to Congo red is 94.27%. In addition, the modified membrane shows an excellent water flux recovery rate and antifouling ability. It performs well in subsequent cycle tests and long-term membrane life tests and can be used repeatedly. Our work has resulted in poly(ether sulfone) membranes with good performance, which show great potential in the treatment of biomedical wastewater and the removal of industrial organic dye wastewater, it provides ideas for the development and application of amphiphilic polymer materials.

Experimental and CFD simulation of glyphosate removal by a filter-press electrocoagulation reactor

The present communication proposes a lumped kinetic and phenomenological model for glyphosate removal in synthetic agro-industrial wastewater using an electrocoagulation process (EC). A traditional filter press-cell electrochemical reactor is used for the EC experimental process. The outcomes of the current density, electrode material, and electrolysis process time were analyzed. The experimental results evidence a better removal performance for the aluminum than the carbon steel, and stationary removal conditions were reached at 40 min with a removal efficiency > 40% considering an input flow of 2 L min−1 and operational cost of 0.172 USD m−3 at 7.5 mA cm−2. The XRD analysis evidenced the interaction between the aluminum ion and the pesticide. The residual aluminum in the supernatant was < 10 mg L−1 at stationary removal conditions. The species distribution inside the reactor is described by the theoretical analysis, which takes into account the simultaneous solution of the Reynolds averaged Navier-Stokes (RANS) and kinetic-based mass conservation equation. Under full electrokinetic control (secondary current distribution), the electrode kinetics characterizing the flux generation of Al3+ on the anode is also taken into consideration. The model proposed here can explain the experimental COD removal attributed to the glyphosate concentration as a function of the aluminum dose due to the applied current density. The model is fitted to experimental data to calculate the kinetic and transport parameters.

Excellent treatment effect of actual wastewater from a pesticide plant using electro-Fenton process catalyzed by natural pyrite

The experiment used natural pyrite as catalyst for electro-Fenton process to treat actual wastewater containing high concentrations of chlorine salts from a pesticide factory in Guangdong province, China. It revealed that under the optimized conditions of initial pH of 3, electrode spacing of 4 cm, and current density of 40 mA/cm2, excellent treatment effect was achieved using 3 g/L pyrite as catalyst with graphite cathode and Ti/RuO2-IrO2-SnO2 anode after a duration of 3 h. Specifically, the removal efficiencies of chemical oxygen demand (COD), absorbance at 478 nm (I478), ammonia nitrogen (AN) and total nitrogen (TN) reached 99.1 %, 99.8 %, 98.9 % and 46.0 % respectively, and instantaneous current efficiency (ICE) at 3 h and energy consumption (EC) were 48.16 % and 97 kWh/kgCOD. Pyrite exhibited good reusability, mainly due to its proper dissolution capacity to renew surface active sites. It was speculated that the nitrogen removal of pesticide wastewater might mainly owe to the oxidation of NH4+ by chlorine/hypochlorite which were based on anode discharge reaction of contained Cl−. The electro-Fenton process catalyzed by natural pyrite showed good potential for efficiently treating the actual pesticide processing plant wastewater with high contents of chlorine salts.

Comparing removal of synthetic anthraquinone dye wastewater in an electrical discharge and UV-LED/WO3 reactors: using statistical Taguchi optimization approach.

Advanced oxidation processes (AOPs) are an available solution for the rapid growth of the water pollution problem. In the present study, the process of UV-LED/WO3 and plasma was comparatively studied to remove reactive blue 19. The photocatalyst process efficiency was analyzed by statistical Taguchi model. The effect of experimental variables of contact time, pH, catalyst dosage, and pollutant dosage was investigated and found that the model is able to explain the process due to the high value of R > 95%, and the optimum condition was at 10 mg/L of dye concentration, 1g/L of catalyst, and 180 min of detention time in which over 75% of degradation was achieved. Based on the model, the more reaction time would increase the reactor performance, while further excessive increase of catalyst dosage over 1 g/L would deteriorate the performance. Obviously, the least amount of pollutant is the most favorable for the treatment reactor. Using plasma process for dye degradation was the next step of the research. Accordingly, the removal rate achieved over 90% of 10 mg/L of initial industrial dye in durational time of 4 min, input voltage 13.5 kV, and pH = 2. The results showed the higher oxidizing capacity of plasma than the conventional photocatalyst process.

Reduction of COD concentration and complete removal of phenol in industrial wastewater utilizing mesoporous TiO2 nanoparticles under UVA illumination

Toxic organic pollutants with low biodegradability are observed and detected in industrial wastewater with high contents. Phenol is one of the toxic organic compounds, and discharging it into the water can be extremely harmful to the environment and the organism's health. In this contribution, the photodegradation of phenol and minimizing COD concentration in industrial wastewater collected from the pharmaceutical industry utilizing mesoporous TiO2 nanoparticles (NPs) contrasted with commercial TiO2 photocatalysts have been conducted under UVA illumination. The results indicated that 100% phenol removal and 60.4% of the total COD were achieved at pH = 6, 1 g/L of catalyst loading, and 10.5 mg/L phenol content, 2476 mg/L of COD content within 140 min of UVA illumination. The phenol photodegradation and COD removal over the mesoporous TiO2, UV-100, and P-25 obeyed a pseudo-first-order model, and their rate constants (k) were determined about 0.0175, 0.0091 and 0.0127 min−1. The k value of mesoporous TiO2 NPs was enhanced 2 and 1.4 folds greater than that of the photocatalysts of UV-100 and P-25. The photodegradation of phenol using mesoporous TiO2 NPs for being recycled five times without losing was acquired, which indicated the obtained mesoporous TiO2 NPs are very stable for long illumination time. The active species' role during photocatalytic degradation phenol and COD removal over mesoporous TiO2 photocatalyst under illumination are the critical oxidative species of •OH and O2•− radicals. Consequently, the COD reduction and complete phenol removal in real industrial wastewater have been verified.

COLOR REMOVAL OF DISPERSE DYEING WASTE WATER BY OZONE IN AN EXAMPLE DYEHAUSE

As a result of rapid population growth and industrialization, wastewater generated in various sectors poses a threat to the environment and living things.Textile industry wastewater comes first among these wastewater sources.These wastewaters contain dyestuffs and different chemicals. These waters, which contain many impurities, must be treated well, otherwise they may cause serious problems in the environments where they are discharged. Various physical, chemical and biological methods are used for color removal in wastewater. However, due to the cost and low efficiency of these methods, researches are carried out on innovative and more economical methods. Among the new technologies, advanced oxidation processes (AOPs) are highly efficient new methods being studied for the purification of certain impurities that cannot be removed by general techniques. AOP methods include photocatalytic reaction with UV, ultrasound, Fenton/Peroxide, ultrasound sound waves and similar reactions. One of these methods is ozonation method. In this study, ozone decolorization of wastewater after disperse dyeing taken from textile dyehouse was investigated. In the determined procedure, the removal of color by ozonation method, which is one of the advanced oxidation methods for wastewater recipes after dyeing, was investigated and the color absorbance and COD values of the samples were examined and the results were evaluated.

Shielding process for the effect of anions on uranium selective recovery and heavy metal removal from simulated mine effluents

The selective separation of uranium from uranium tailing wastewater is of great importance for environmental protection and nuclear energy development. The complexation of Cl−, SO42−, NO3–, and PO43− with UO22+ seriously hindered the achievement of this goal. Herein, a process for achieving it with the coexistence of anions and cations by shielding the influence of anions was designed. Thermodynamic calculations indicated that CO32– could enhance the retention of uranium in the solution by complexing with UO22+ and capturing UO22+ in UO2SO4 and UO2HPO4 to form water-soluble uranyl-carbonate. The capturing ability of CO32– was not diminished by the increase in anion concentration. And the electrochemical experiments revealed the high efficiency of uranium electrochemical extraction in the above system. In addition, the results showed that uranium could be separated from Co2+, Cd2+, and Ni2+ ions under the coexistence of Cl−, SO42−, NO3–, and PO43−, thus achieving the selective separation of uranium in the wastewater. And the retention ratio of impurity cations in the liquid phase after separation was less than 0.003. Overall, this method provides new insights into the selective separation of uranium and heavy metal removal in real uranium tailings wastewater.

Iron-sulfur mediated antibiotic resistance genes attenuation and autotrophic denitrification mechanisms in bioelectrochemical systems

Aiming at the problems of antibiotic resistance genes (ARGs) transfer, mobile gene elements (MGEs) and nitrogen removal in livestock wastewater, pyrite was introduced into the bioelectrochemical constructed wetland, mainly focusing on the mechanism of ARGs transfer and autotrophic denitrification in bioelectrochemical system. The results indicated that pyrite promoted the degradation of antibiotics while inhibiting the efflux of ARGs and MGEs in effluent. The removal rate of antibiotics in pyrite-mediated constructed wetland coupled with microbial fuel cell (PCW-MFC) was 26.84 % and 21.20 % higher than constructed wetland-microbial fuel cell (CW-MFC) and pyrite-mediated constructed wetland (PCW). Metagenomic analysis revealed that the abundance of ARGs in effluent and anodic microorganism in PCW-MFC was effectively controlled by inhibiting the expression of genes encoding antibiotic efflux (macB, tetA, smeS). The expression levels of periplasmic nitrate reduction genes (napA, napB) and encoding cytochrome c nitrite reductase small subunit genes (nrfH) in PCW-MFC were much higher than CW-MFC. The total expression of ARGs in CW-MFC anode biofilms was 35.77 % higher than PCW-MFC, indicating that the system can effectively reduce the spread of ARGs and abate environmental risks. The findings can provide theoretical reference for the control of ARGs and efficient nitrogen removal in livestock wastewater.