High Removal Performance Research Articles

Adaptation of anammox consortia in microbial fuel cell to low temperature: Microbial community and predictive functional profiling

The purpose of this study was to explore the tolerance mechanism of anammox consortia in microbial fuel cell (MFC) system at low temperature. Data showed that nearly 80 % total nitrogen removal was achieved after the temperature decreased from 30 °C to 15 °C. The nitrogenremovalrate (NRR) of the system was decreased by 26.3 %, from 0.441 kgN·m−3·d−1 at 30 °C to 0.325 kgN·m−3·d−1 at 15 °C. Isotope experiment in 15NH4+-containing reactor found that much more 29N2 were produced than 30N2, confirming that anammox was the main 15NH4+ removal pathway and electrochemical oxidation participate in this process. High throughput sequencing analysis indicated the low temperature stimulated the enrichment of heterotrophic bacteria, such as Comamonadaceae and Rhodobacteraceae. While the relative abundance of Candidatus Brocadia, typical anammox bacteria, decreased significantly. Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis showed that the low temperature induced a more efficient expression in synthesis of unsaturated fatty acids (UFAs) and ABC membrane transports. This study indicates that anammox consortia are likely to maintain high nitrogen removal performance of MFC system by changing the proportion of membrane composition and EPS exportation.

Iron-rich sludge biochar triggers sodium percarbonate activation for robust sulfamethoxazole removal: Collaborative roles of reactive oxygen species and electron transfer

The efficient removal of sulfamethoxazole (SMX) from swine farming wastewater is a major emerging environmental issue. This study successfully developed Fe-rich sludge biochar (Fe-BC) from dewatered iron-containing sewage sludge cake, in order to activate sodium percarbonate (SPC) for rapid SMX degradation in swine farming wastewater. Under optimal conditions of 0.5 g/L Fe-BC and 0.3 mM SPC at pH of 3.0, Fe-BC/SPC process achieved highly efficient SMX degradation within 5 min, reaching 100 % SMX degradation efficiency with kobs of 1.1439 min−1. The Fe-BC/SPC process exhibited recyclability and a high level of resistance to natural wastewater conditions. The main mechanism included adsorption and oxidation process. The SMX was probably adsorbed on the Fe-BC surface. Also, SPC activation by Fe-BC for SMX degradation was found to include a radical-driven pathway dominated by •OH and a non-radical pathway governed by direct electron transfer. Furthermore, the high rate of SMX degradation in the Fe-BC/SPC process was attributed to Fe2+ generation via the Fe3+/Fe2+ cycle and efficient electron transfer through oxygenated functional groups. Four SMX degradation pathways (i.e., hydroxylation, –NH2 group oxidation, ON bond and NS bond cleavage reactions) were proposed. The Fe-BC/SPC process exhibited high SMX removal performance and low-toxicity with swine farming wastewater. Overall, this study shows that the development of Fe-BC/SPC as a promising and efficient system for SMX degradation in practical swine farming wastewater treatment applications.

High-performance removal of phenol from aqueous solutions using EG- and PEG-functionalized biochar: equilibrium, kinetic and thermodynamic study with optimization by response surface methodology (RSM)

High-performance removal of phenol from aqueous solutions using EG- and PEG-functionalized biochar: equilibrium, kinetic and thermodynamic study with optimization by response surface methodology (RSM)

Radially aligned hierarchical N-doped porous carbon beads derived from oil-sand asphaltene for long-life water filtration and wastewater treatment

The application of waste-derived highly efficient adsorbent for organic pollutants removal from water and wastewater is presented. Highly porous carbon beads with radially aligned macrochannels were prepared from asphaltene. Well-ordered inwardly aligned macrovoids favored solute diffusion and maximized the liquid accommodation capacity. A further N-doping could modulate the sorbent hydrophilicity leading to an outstanding absorption performance for a range of organic solvents and oily chemicals. N-doped carbon beads were effective sorbents of lopinavir (LNV) and ritonavir (RNV) from water and wastewater. The process of sorption was fast, and the highest removal was noted for RNV than LPV. N-doping favored LNV and RNV adsorption due to the increased porous structure of N-doped asphaltene beads. The chemisorption of both LPV and RTV was a rate-limiting step. The presence of co-pollutants in treated wastewater enhanced LPV and RNV removal and an up to 470 % increase was noted. The presence of LPV or RTV in distilled water was not toxic to Aliivibrio fischeri or even can stimulate their growth. However, after the adsorption process, the solution of RTV reduced its toxicity significantly and the final solution was not toxic. The opposite effect was noted for LPV. Given the repeatability, high removal performance, and cost-effectiveness of the asphaltene-based carbon microtubes when compared to other well-known sorbents such as carbon nanotubes, they demonstrated great potential as a low-cost and effective agent for long-life water filtration and wastewater treatment.

Removal of Antibiotics from Aqueous Solutions by Bentonite Supported-Nanoscale Zero-Valent Iron

Nowadays, antibiotics are extensively used in human and animal medicine. The unconscious consumption of antibiotics and their mixing with water sources without adequate treatment have caused environmental problems. Several chemical and physical treatment methods applied for the removal of antibiotics from aqueous media offer alternative solutions by improving the treatment process and using new materials. As in many areas, nanomaterials are also used in treatment methods such as sorption, degradation, and oxidation. Among the nanomaterials, nano zero-valent iron (nZVI) is frequently preferred in treatment processes due to its abundance, cheapness, ease of application, and high removal performance. Besides its many advantages, nZVI agglomerates in the aqueous phase and exhibits unstable behaviors. This limits the surface area required for antibiotic removal and reduces the removal efficiency. In recent years nZVI has been used in water treatment technologies by being modified with many support materials such as bentonite to minimize particle agglomeration. Bentonite is clay-based support material that provides high removal efficiency and reduces the cost of treatment due to its abundance in nature. In this study, antibiotic pollution and treatment methods in water resources were reviewed and the antibiotic removal performances of bentonite-supported nVZI were investigated. In the studies, it was concluded that the antibiotic removal efficiency increased with the use of support materials.

Zero additional maintenance stormwater biofilters: from laboratory testing to field implementation

Abstract Stormwater biofilters are one of the most widely used nature-based solutions for urban water management. In the last 20 years, biofilters have been extensively studied for their pollutant removal performance; however, their application in the field is limited by high maintenance requirements. In this work, we propose the concept of zero additional maintenance (ZAM) biofilters as a solution to this challenge. To understand the design and operation of ZAM biofilters, a three-stage research programme was conducted to (i) examine filter media configurations that could protect against surface clogging, (ii) test the pollutant removal performance of a variety of lawn grasses, and (iii) validate the laboratory findings through field monitoring. The results showed that a protective filter media layer delayed the onset of clogging. Five lawn grasses – Kenda Kikuyu, Empire Zoysia, Santa Ana Couch, Village Green Kikuyu and Palmetto Soft Leaf Buffalo – were found to effectively reduce nitrogen concentrations and meet other local pollution reduction requirements. Monitoring of three field-scale ZAM biofilters confirmed their high nutrient and heavy metal removal performance. Overall, the findings of these three studies confirm the potential for well-designed ZAM biofilters to achieve stormwater management requirements with no additional maintenance compared with standard street landscaping.

Green synthesis of zero-valent iron nanoparticles by Cleistocalyx operculatus leaf extract using microfluidic device for degradation of the Rhodamine B dye

Environmental pollution, in particular, the wastewater from the textile and dyeing production process is causing serious issues for the ecosystem and humans. It has been well-demonstrated that zero-valent iron nanoparticles (nZVI) are one of the most promising materials in the treatment of environmental pollutants. In this work, the Cleistocalyx operculatus leaf extract was employed as a green reductant for the synthesis of the nZVIs nanoparticles from iron ions precursor. Notably, a microfluidic device was also used as micro-reactor for the synthesis process of the nanoparticles, making it easy to control and optimise the morphologies and sizes of nZVI. The morphology and crystallinity of nZVI were characterised by scanning electron microscopy (SEM) and x-ray diffraction (XRD), respectively. The nZVIs prepared in a microfluidic reactor using Cleistocalyx operculatus leaf extract as reductant were in plate-like structure with the thickness of around 5 nm and the diameter in range of hundred nanometers. The removal efficiency of Rhodamin B (RhB) dye by the prepared nZVI was determined by ultraviolet-visible (UV–vis) spectroscopy. The results showed that the nZVI revealed high removal performance toward RhB with removal efficiency of higher than 90% after 30 min of treatment. The effects of dye’s concentration, time, and pH solution on the treatment performance of RhB were also studied.

Fabrication of modified carbon nano tubes based composite using ionic liquid for phenol removal

Carbon nano tubes are functionalized to enhance their surface properties and target specificity. In this research, a novel ionic liquid functionalized carbon nanotube (IL-CNT) material was synthesized using 1-Hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide and investigated for the phenol removal. The parametric experiments were performed to identify the optimal conditions for high removal performance. With an initial concentration of 50 mg/L and an IL-CNT dosage level 100 mg, 95.36% phenol removal was attained at optimal pH 6.0. The occurrence of monolayer attachment was verified through equilibrium studies. The Langmuir isotherm parameters are evaluated as qm =109.9 mg/g and KL = 0.196 L/mg. The kinetic experiments followed Pseudo Second Order model (R2 > 0.990). The synthesized nanomaterial was characterized using Scanning Electron Microscopic imaging, Fourier Transform Infra-Red spectra, X-Ray Diffraction analysis and Thermo Gravimetric Analysis.

Low-temperature-resistance granulation of activated sludge and the microbial responses to the granular structural stabilization

Completely loss of granular structural stability and reliable start-up of aerobic granular sludge (AGS) system are considered as the biggest challenges for its engineering application under seasonal temperature variation, especially extremely low temperatures. In this study, two identical sequencing batch reactors (SBR) were successfully start-up at 10 °C (R1) and 25 °C (R2), respectively, and then operated under a strategy of stepwise change of temperatures to investigate the stability of the granular sludge by examining its microbial characteristics, bis (3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP), extracellular polymeric substance (EPS) and sludge physiochemical properties. The results showed that AGS formed under the low temperature preferentially secrete EPS and c-di-GMP for stable granulation and improvement of its resistance to temperature changes. Meanwhile, R1 successfully obtained aerobic granulation with high biomass concentration and superior settleability, as well as high pollutant removal performance. In comparison, R2 took a longer time for granulation and was subjected to serious disintegration of AGS. The matrix structure partially formed by filamentous bacteria during the start-up stage in R1 was one of major reasons for its own superiority beyond R2 in granulation. Slow-growing organisms such as autotrophic nitrifying and Anammox bacteria, phosphorus accumulation organisms, EPS-producing genera, and c-di-GMP pathway-dependent genera, were exclusively enriched in the R1 and resulted in higher pollutants removal efficiencies and stable structure, whereas Sphaerotilus dominated in R2 that related closely with its unstable performance. Therefore, the strategy based on the stepwise change of temperatures from extremely low temperatures may be one feasible way for the sustainable application of AGS system, which is of significance to address the challenging problems of AGS applications.

The role of TiO2 NPs catalyst and packing material in removal of phenol from wastewater using an ozonized bubble column reactor

Phenol is present as a highly toxic pollutant in wastewater, and it has a dangerous impact on the environment. In the present research, the phenol removal from wastewater has been achieved using four treatment methods in a bubble column reactor (treatment by ozone only, using packed bubble column reactor with ozone, utilizing ozone with TiO2 NPs catalyst in the reactor without packing, and employing ozone with TiO2 NPs in the presence of packing). The effects of phenol concentration, ozone dosage, TiO2 NPs additions, and contact time on the phenol removal efficiency were determined. It was found that at a contact time of 30 min, the phenol removal was 60.4, 74.9, 86.0, and 100% for the first, second, third, and fourth methods, respectively. The results indicated that the phenol degradation method using catalytic ozonation in a packed bubble column with TiO2 NPs is the best treatment method. This study demonstrated the advantages of using packing materials in a bubble column reactor to enhance the mass transfer process in an ozonation reaction and then increase the phenol removal efficiency. Also, the presence of TiO2 NPs as a catalyst improves the ozonation process via the production of hydroxyl routs. Additionally, the reaction kinetics of ozonation reaction manifested that the first order model is more applicable for the reaction. Eventually, the packed bubble column reactor in the presence of TiO2 NPs catalyst provided a highperformance removal of phenol with a high economic feasibility.

Modified g-C3N4 with boron doping for efficient simultaneous catalytic reduction of Ag+ and organic pollutants

In this study, band gap engineering and surface modification were studied to promote dye removal efficiency of g-C3N4, a visible-light responsive photocatalyst. The modification of band gap energy and chemical surface by mean of thermal reaction with NaBH4 in order to introduce B dopants in the g-C3N4 framework was successful. The pristine g-C3N4 prepared from urea (U–CN) and from melamine (M − CN) demonstrated RhB degradation efficiency (DE%) of 95.6% and 38.2%, respectively, under illumination for 60 min by daylight lamp. Strikingly, B-doped g-C3N4 presented high performance in dye removal without light. Synergistically, the modified band gap by B doping, surface decoration with -BH4−, and high surface area of g-C3N4, altogether maximize RhB and MB dye removal efficiency (DR%) up to 98.3% and 66.0%, respectively. The reduction ability of the modified catalyst is also illustrated in the transformation of silver ion into silver particles under light irradiation. Finally, the modified g-C3N4 can act as high performance photocatalyst and co-catalyst supporting substrate for applying in environmental and energy applications.

Assessing quinoline removal performances of an aerobic continuous moving bed biofilm reactor (MBBR) bioaugmented with Pseudomonas citronellolis LV1

This study evaluated the bioaugmentation potential of a quinoline-degrading strain Pseudomonas citronellolis LV1 inoculation into activated sludge for treating quinoline wastewater, and results indicated the inoculation of LV1 in aerobic continuous MBBR could substantially improve the quinoline removal performance with an improved removal efficiency of 34% averagely when quinoline was used as the sole carbon and nitrogen source. Additionally, efficient removal of quinoline in enhanced MBBR occurred at the influent pH of 7.0–8.0, hydraulic retention time (HRT) of 24–28 h and influent quinoline concentration of 100–700 mg·L−1. High-throughput sequencing analysis indicated that bioaugmentation could increase microbial diversity and shape the microbial community structure. Although the inoculant LV1 did not remain its dominance in stage III, bioaugmentation indeed induced the formation of effective microbial community, and the indigenous microbes including Flavobacterium, Pseudoxanthomonas, Pseudomonas, Vermamoeba, Dyadobacter and Sphingomonas might play the key role in quinoline removal. According to the PICRUSt, the enhanced genes encoding aromatic ring-cleavage enzyme, especially for N-heterocyclic ring-cleavage enzymes, could lead to the improved removal performance of quinoline in bioaugmentation stage. Moreover, the enhanced MBBR treated well actual coking wastewater, as indicated by high removal performance of quinoline, phenol and COD.

Ultrasound-Assisted High-Performance Removal of Doxorubicin Using Functionalized Graphene Oxide-Fe3O4 Magnetic Nano-sorbent

Ultrasound-Assisted High-Performance Removal of Doxorubicin Using Functionalized Graphene Oxide-Fe3O4 Magnetic Nano-sorbent

High-performance Removal of Tetracycline Enabled by Fe0 Nanoparticles Supported on Carbon@ZIF-8

High-performance Removal of Tetracycline Enabled by Fe0 Nanoparticles Supported on Carbon@ZIF-8

Co-immobilization of laccase and PEG modified COFs into Cu doped gel beads to achieve synergistic effect of photocatalysis and enzymatic catalysis for pollutants removal

In this work, PEG modified photocatalytic covalent organic framework (PEG@CTF-OMe) was co-immobilized with laccase into Cu doping calcium alginate gel beads (Ca/Cu-PEG@CTF-OMe-lac). PEG@CTF-OMe improved the light stability of laccase under blue light irradiation, and external introduction of copper into gel beads stabilized the conformation and improved pH adaptability of laccase. With the help of 2,2-binamine-di-3-ethylbenzothiazolin-6-sulfonic acid (ABTs), the immobilized laccase (Ca/Cu-PEG@CTF-OMe-lac) presented outstanding synergistic removal of pollutants by photocatalysis and enzymatic catalysis, as well as ABTs radicals generation promoting by copper ions in the laccase-mediator system. The removal recyclability performance assay found that the Ca/Cu-PEG@CTF-OMe-lac gel beads had more than 80 % removal efficiency for phenol, 4-chlorophenol, 2,4-dichlorophenol, nonyl phenol, bisphenol A and indole in water at 25 °C after 5 cycles, when the concentration reached as high as 70 mg/L, 60 mg/L, 120 mg/L, 100 mg/L, 100 mg/L and 100 mg/L, respectively. The high synergistic removal performance obtained by the gel beads co-immobilizing laccase and photocatalytic CTFs showed greater practical application value.

Shellfish waste-derived mesoporous chitosan for impressive removal of arsenic(V) from aqueous solutions: A combined experimental and computational approach

Novel shellfish waste-derived chitosan (CS) has been developed to adsorb As(V) from simulated wastewater under evaluating adsorption process parameters. The coexistence of some competing ions, like SiO32-, Cl-, NO3– and PO43- as well as the regeneration capacity of the spent adsorbent, was explored. The experimental data were modeled using several kinetics and isotherm models to understand the mechanism related to the uptake process. As(V) uptake was relatively rapid and highly dependent on pH. The Avrami-fractional-order expression supported data best, while the Liu equation described well isotherm data at pH 5.0. The maximum uptake capability (Liu) was 12.32 mg/g, and the highest removal performance (99 %) was obtained at optimum pH 5.0. Molecular dynamics simulations were performed to more clearly illuminate the atomic-level interactions between arsenic species and CS surface in both acidic and basic mediums. After four adsorption–desorption cycles, CS exhibited more than 90 % As(V) removal efficiency. The results of this study indicates that low cost shellfish derived chitosan is promising for efficient removal of As(V) from water body and can be used to remove other pollutants from watewater.

Preparation of hydrochar bio-based catalyst for fenton process in dye-containing wastewater treatment

The use of synthetic dyes in the textile industry pollutes a huge amount of water. Thus, wastewater discharged from many textile companies to the receiving environment without being treated causes serious environmental and human health problems. The development of new techniques has become imperative. In this study, it was aimed to remove anionic dye (RR180) and cationic dye (BR18) by Fenton-like and adsorption process with hydrochars obtained from laurel leaves and watermelon peels. In the comparison of the adsorption and Fenton-like processes used in the dye removal of the produced bio-based materials, the Fenton-like process was selected in order to enhance the highest removal efficiency. The effects of various operating factors such as solution pH, amount of catalysts, hydrogen peroxide (H2O2) concentration, and initial dye concentration were evaluated on both dyes removal. The experimental results demonstrated that 99.8% RR180 dye and 98.8% BR18 dye removal efficiency were observed for an initial dye concentration of 100 mg/L with an adsorbent concentration of 1 g/L, H2O2 concentration of 15 μL/L, and optimum pH at the end of 60 min of reaction time. It was observed that an increase in initial dye concentration caused to decrease the dye removal efficiency. The optimum pH for the highest RR180 and BR18 dye removal was 4 and 6, respectively. It was observed that the increase in H2O2 concentration in the solution also decreased the dye removal efficiency. It turned out that catalysts obtained from hydrochars are an effective process for the high removal performance of cationic and anionic dyes.

Electrocoagulation of peatland runoff: Statistical optimization and economic analysis

Irish peatlands play a crucial role in delivering drinking water sources to large conurbations. However, peatland runoff contains a high concentration of natural organic matter (NOM), which is problematic for drinking water treatment as it decreases the effectiveness of conventional treatment and can lead to the formation of suspected carcinogenic disinfection by-products (DBPs). In this study, a low-cost and highly efficient electrocoagulation (EC) unit has been used to treat raw peatland runoff. EC processes were designed, evaluated and optimized via the response surface methodology (RSM). Total operation cost was calculated after the RSM process. Box-Behnken design (BBD) was employed in RSM to analyse the effect of the applied voltage, reaction time, and electrolyte (NaCl) addition on the removal of total organic carbon (TOC) and colour at 465 nm. Two second order polynormal equation models were fitted with a high R2 of 0.93 (TOC) and 0.96 (colour). The highest removal performance (88.44 % of TOC and 98.93 % of colour) was observed when the applied voltage and reaction time were at their middle level (i.e. 3 V and 35 min). The optimum values of operating variables obtained by the multi-objective optimization were a NaCl concentration of 130.4 mg/L, an applied voltage of 2.0 V and a reaction time of 47.0 min. Under these conditions, 85.2 % of TOC and 98.1 % of true colour (at 465 nm) was removed in the laboratory at an operating cost of 0.50 €/m3, representing a higher TOC and colour removal and lower total operating cost than previous studies. The cost of NaCl contributed the most of the three factors to the total cost of the treatment process.

Effects of long-term exposure to low-concentration PS-NPs on anammox granular sludge: Resistance and inhibition depend on PS-NP accumulation

At present, the effects on anammox granular sludge (AnGS) of long-term exposure to low-concentration polystyrene nanoplastics (PS-NPs) and the associated mechanisms are still unclear. In this paper, the effects of continuous PS-NP exposure (1–2 mg/L, 225 d) on the nitrogen removal performance, activity and granule stability of an AnGS reactor were studied. In the first 100 d, the nitrogen removal performance of the reactor was stable, and the specific anammox activity (SAA) gradually increased. After 225 d, the nitrogen removal performance of the reactor decreased, and the AnGS SAA NH4 + -N and SAA NO2 - -N decreased by 44.5% and 57.6%, respectively, compared with those at 100 d. Long-term PS-NP exposure increased the oxidative stress level of cells and led to membrane damage. Decreases in the content of extracellular polymeric substances (EPS) and extracellular protein (PN) hydrophobicity led to a decrease in the aggregation performance of AnGS. PS-NPs adhered to EPS to form a dense structure, blocking AnGS mass transfer channels and reducing AnGS strength, and some granular sludge was cracked. Candidatus Kuenenia and Candidatus Jettenia were inhibited, and their abundance decreased. The effects of PS-NP exposure on AnGS depended on the accumulation of PS-NPs, and significant inhibitory effects were observed at 118 mg PS-NPs/g VSS. This work helps to assess the potential risk of long-term AnGS exposure to low-concentration PS-NPs and is of great significance to maintain the high nitrogen removal performance and stability of AnGS. • The effects of AnGS exposure to 1–2 mg/L PS-NPs for 225 d were studied. • Increased accumulation of PS-NPs led to the inhibition of AnGS. • PS-NPs reduced the SAA and stability of AnGS by plugging pores. • Decreases in EPS content and PN hydrophobicity were the main contributors to AnGS disruption. • AnGS disruption relieved the mass transfer resistance caused by PS-NPs.

High adsorption and photocatalytic degradation abilities of amorphous Ta2O5 nanospheres under simulated solar light irradiation

In this study, the crystallized and amorphous Ta2O5 nanospheres were successfully synthesized by a simple alcohol-thermal reaction. The particle sizes of amorphous Ta2O5 nanospheres were controlled by adjusting the PVP amount in the synthetic system. The removal abilities of the Ta2O5 towards organic dyes were assessed by measuring the adsorption and the photocatalytic degradation performance towards methylene blue (MB) under dark condition and simulated solar light irradiation, respectively. The results indicate that the amorphous Ta2O5 prepared with 1:5 PVP (a-Ta2O5 5PVP) exhibited extremely high adsorption abilities and photocatalytic degradation performances, compared to the crystallized and other amorphous Ta2O5 nanospheres. The excellent MB removal ability of a-Ta2O5 5PVP can be attributed to high specific surface area, extra O vacancies, enhanced visible light absorption, more photo-generated electrons and low charge transfer resistance. This study may shed light on a simple but low-cost preparation strategy for amorphous Ta2O5 nanospheres suitable for the future practical application on wastewater treatment and provide deep insights on the underlying reasons for the high removal performance to organic dyes.