The potential for synthesized invasive plant biochar with hydroxyapatite to mitigate allelopathy of Solidago canadensis.

Few studies tried to explore the mitigation effect and underlying mechanisms of biochar and their complex for negative allelopathy from invasive plants, which may provide a new way in the invasive plant management. Herein, an invasive plant (Solidago canadensis)-derived biochar (IBC) and its composite with hydroxyapatite (HAP/IBC) were synthesized by high temperature pyrolysis, and characterized by scanning electron microscopy, energy dispersion spectrometer, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Then, both the batch adsorption and pot experiments were conducted to compare the removal effects of kaempferol-3-O-ß-D-glucoside (C21 H20 O11 , kaempf), an allelochemical from S. canadensis, on IBC and HAP/IBC, respectively. HAP/IBC showed a stronger affinity for kaempf than IBC due to its higher specific surface area, more functional groups (P-O, P-O-P, PO4 3- ), stronger crystallization [Ca3 (PO4 )2 ]. The maximum kaempf adsorption capacity on HAP/IBC was six times higher than on IBC (10.482 mg/g > 1.709 mg/g) via π-π interactions, functional groups, and metal complexation. The kaempf adsorption process could be fitted best by both pseudo-second-order kinetic and Langmuir isotherm models. Furthermore, HAP/IBC addition into soils could enhance and even recover the germination rate and/or seedling growth of tomato inhibited by negative allelopathy from the invasive S. canadensis. These results indicate that the composite of HAP/IBC could more effectively mitigate the allelopathy from S. canadensis than IBC, which may be a potential efficient approach to control the invasive plant and improve invaded soils.

Exploring the influence of sulfadiazine-induced stress on antibiotic removal and transformation pathway using microalgae Chlorella sp.

Sulfadiazine (SDZ) is a kind of anti-degradable antibiotics that is commonly found in wastewater, but its removal mechanism and transformation pathway remain unclear in microalgal systems. This study investigated the effects of initial algae concentration and SDZ-induced stress on microalgal growth metabolism, SDZ removal efficiency, and transformation pathways during Chlorella sp. cultivation. Results showed that SDZ had an inhibitory effect on the growth of microalgae, and increasing the initial algal biomass could alleviate the inhibitory effect of SDZ. When the initial algal biomass of Chlorella sp. was increased to 0.25 g L-1, the SDZ removal rate could reach 53.27%-89.07%. The higher the initial algal biomass, the higher the SOD activity of microalgae, and the better the protective effect on microalgae, which was one of the reasons for the increase in SDZ removal efficiency. Meanwhile, SDZ stress causes changes in photosynthetic pigments, lipids, total sugars and protein content of Chlorella sp. in response to environmental changes. The main degradation mechanisms of SDZ by Chlorella sp. were biodegradation (37.82%) and photodegradation (23%). Most of the degradation products of SDZ were less toxic than the parent compound, and the green algae were highly susceptible to SDZ and its degradation products. The findings from this study offered valuable insights into the tradeoffs between accumulating microalgal biomass and antibiotic toxic risks during wastewater treatment, providing essential direction for the advancement in future research and full-scale application.

Chromium immobilization from wastewater via iron-modified hydrochar: Different iron fabricants and practicality assessment.

The recycling of industrial solid by-products such as red mud (RM) has become an urgent priority, due to their large quantities and lack of reutilization methods can lead to resource wastage. In this work, RM was employed to fabricate green hydrochar (HC) to prepare zero-valent iron (ZVI) modified carbonous materials, and conventional iron salts (IS, FeCl3) was applied as comparison, fabricated HC labeled as RM/HC and IS/HC, respectively. The physicochemical properties of these HC were comprehensively characterized. Further, hexavalent chromium (Cr(VI)) removal performance was assessed (375.66 and 337.19 mg/g for RM/HC and IS/HC, respectively). The influence of dosage and initial pH were evaluated, while isotherms, kinetics, and thermodynamics analysis were also conducted, to mimic the surface interactions. The stability and recyclability of adsorbents also verified, while the practical feasibility was assessed by bok choy-planting experiment. This work revealed that RM can be used as a high value and green fabricant for HC the effective removal of chromium contaminants from the wastewater.

Magnetic biochar serves as adsorbents and catalyst supports for the removal of antibiotics from wastewater: A review.

Numerous antibiotics are being released into the natural environment through wastewater. As antibiotic usage increases annually, its detrimental impact on the environment is escalating. Addressing environmental sustainability and human health requires significant attention towards antibiotic removal. In recent years, magnetic biochar (MBC) has gained widespread application in water treatment due to its exceptional adsorption and catalytic degradation capabilities. Antibiotics such as sulfamethoxazole (SMX), tetracycline (TC), ciprofloxacin (CIP), and others commonly exhibit an adsorption capacity by MBC ranging from 5 mg/g to 900 mg/g. Moreover, MBC typically removes over 90% of these antibiotics within 60 min. The effectiveness of antibiotic removal is significantly influenced by various preparation and modification methods. Furthermore, the incorporation of magnetism enables the material to be recycled and reused multiple times, thereby reducing consumption costs. This article discusses recent studies on antibiotic removal using MBC. It has been observed that variations in the selection of raw material and preparation procedures significantly affect antibiotic removal, while the mechanisms involved in antibiotic removal remain ambiguous. Additionally, it has been noted that the removal process may lead to secondary pollution and high preparation costs. Therefore, this review comprehensively outlines the utilization of MBC in the removal of antibiotics from wastewater, including aspects such as modification, preparation, removal mechanism, and factors influencing removal, and providing recommendations for antibiotic development. The aim is to offer researchers a clear understanding to advance the field of MBC materials.

Membrane modification in enhancement of virus removal: A critical review.

Many waterborne diseases are related with viruses, and COVID-19 worldwide has raised the concern of virus security in water into the public horizon. Compared to other conventional water treatment processes, membrane technology can achieve satisfactory virus removal with fewer chemicals, and prevent the outbreaks of viruses to a maximal extent. Researchers developed new modification methods to improve membrane performance. This review focused on the membrane modifications that enhance the performance in virus removal. The characteristics of viruses and their removal by membrane filtration were briefly generalized, and membrane modifications were systematically discussed through different virus removal mechanisms, including size exclusion, hydrophilic and hydrophobic interactions, electronic interactions, and inactivation. Advanced functional materials for membrane modification were summarized based on their nature. Furthermore, it is suggested that membranes should be enhanced through different mechanisms mainly based on their ranks of pore size. The current review provided theoretical support regarding membrane modifications in the enhancement of virus removal and avenues for practical application.

Microplastics in landfill leachate: Occurrence, health concerns, and removal strategies.

Landfills are commonly used to manage solid waste, but they can contribute to microplastic (MPs) pollution. As plastic waste degrades in landfills, MPs are released into the surrounding environment, contaminating soil, groundwater, and surface water. This poses a threat to human health and the environment, as MPs can adsorb toxic substances. This paper provides a comprehensive review of the degradation process of macroplastics into microplastics, the types of MPs found in landfill leachate (LL), and the potential toxicity of microplastic pollution. The study also evaluates various physical-chemical and biological treatment methods for removing MPs from wastewater. The concentration of MPs in young landfills is higher than in old landfills, and specific polymers such as polypropylene, polystyrene, nylon, and polycarbonate contribute significantly to microplastic contamination. Primary treatments such as chemical precipitation and electrocoagulation can remove up to 60-99% of total MPs from wastewater, while tertiary treatments such as sand filtration, ultrafiltration, and reverse osmosis can remove up to 90-99%. Advanced techniques, such as a combination of membrane bioreactor, ultrafiltration, and nanofiltration (MBR + UF + NF), can achieve even higher removal rates. Overall, this paper highlights the importance of continuous monitoring of microplastic pollution and the need for effective microplastic removal from LL to protect human and environmental health. However, more research is needed to determine the actual cost and feasibility of these treatment processes at a larger scale.

Treatment of hazardous landfill leachate containing 1,4 dioxane by biochar-based photocatalysts in a solar photo-oxidation reactor.

This study investigates a combined photocatalytic and adsorption system to maximize the removal of 1,4 dioxane from hazardous landfill leachate (HLL). The production of transformation products was also investigated to obtain a comprehensive evaluation of the treatment system. Copper/iron doped zinc oxide (Cu-Fe-ZnO) was introduced to biochar to form a hybrid materials and used to treat HLL contaminated with 1,4 dioxane of 355.0 ± 11.7 mg/L. The Cu-Fe-ZnO/biochar removed 93.1 ± 8.7% of 1,4 dioxane at a dose of 0.6 g/L within 90 min, as compared with only 42.7 ± 3.3% by 1.2 g/L of bare biochar within 210 min. The Cu-Fe-ZnO/biochar degraded 1,4 dioxane into ethylene glycol, glycolic acid, and formic acid. The 1,4 dioxane removal mechanisms were investigated using the density functional theory, demonstrating that doping of ZnO with metal atoms (Cu-Fe) narrowed the bandgap from 3.307 eV to 2.736 eV. The enhanced photocatalytic activity of ZnO was also supported by the role of biochar in increasing the reactive species and adsorbing the pollutant molecules. The high degradation efficiency of 1,4 dioxane using small catalyst doses with short reaction times would reduce the treatment cost and improve the system's applicability for treating HLL and industrial effluents.

Microalgae systems - environmental agents for wastewater treatment and further potential biomass valorisation.

Water is the most valuable resource on the planet. However, massive anthropogenic activities generate threatening levels of biological, organic, and inorganic pollutants that are not efficiently removed in conventional wastewater treatment systems. High levels of conventional pollutants (carbon, nitrogen, and phosphorus), emerging chemical contaminants such as antibiotics, and pathogens (namely antibiotic-resistant ones and related genes) jeopardize ecosystems and human health. Conventional wastewater treatment systems entail several environmental issues: (i) high energy consumption; (ii) high CO2 emissions; and (iii) the use of chemicals or the generation of harmful by-products. Hence, the use of microalgal systems (entailing one or several microalgae species, and in consortium with bacteria) as environmental agents towards wastewater treatment has been seen as an environmentally friendly solution to remove conventional pollutants, antibiotics, coliforms and antibiotic resistance genes. In recent years, several authors have evaluated the use of microalgal systems for the treatment of different types of wastewater, such as agricultural, municipal, and industrial. Generally, microalgal systems can provide high removal efficiencies of: (i) conventional pollutants, up to 99%, 99%, and 90% of total nitrogen, total phosphorus, and/or organic carbon, respectively, through uptake mechanisms, and (ii) antibiotics frequently found in wastewaters, such as sulfamethoxazole, ciprofloxacin, trimethoprim and azithromycin at 86%, 65%, 42% and 93%, respectively, through the most desirable microalgal mechanism, biodegradation. Although pathogens removal by microalgal species is complex and very strain-specific, it is also possible to attain total coliform and Escherichia coli removal of 99.4% and 98.6%, respectively. However, microalgal systems' effectiveness strongly relies on biotic and abiotic conditions, thus the selection of operational conditions is critical. While the combination of selected species (microalgae and bacteria), ratios and inoculum concentration allow the efficient removal of conventional pollutants and generation of high amounts of biomass (that can be further converted into valuable products such as biofuels and biofertilisers), abiotic factors such as pH, hydraulic retention time, light intensity and CO2/O2 supply also have a crucial role in conventional pollutants and antibiotics removal, and wastewater disinfection. However, some rationale must be considered according to the purpose. While alkaline pH induces the hydrolysis of some antibiotics and the removal of faecal coliforms, it also decreases phosphates solubility and induces the formation of ammonium from ammonia. Also, while CO2 supply increases the removal of E. coli and Pseudomonas aeruginosa, as well as the microalgal growth (and thus the conventional pollutants uptake), it decreases Enterococcus faecalis removal. Therefore, this review aims to provide a critical review of recent studies towards the application of microalgal systems for the efficient removal of conventional pollutants, antibiotics, and pathogens; discussing the feasibility, highlighting the advantages and challenges of the implementation of such process, and presenting current case-studies of different applications of microalgal systems.

Lanthanum carbonate hydroxide/magnetite nanoparticles functionalized porous biochar for phosphate adsorption and recovery: Advanced capacity and mechanisms study.

As the increase of global industrial activities, phosphate from industrial wastes such as sewage sludge has become one of the limiting factors for water eutrophication. Herein, lanthanum carbonate hydroxide (La(CO3)OH)/magnetite (Fe3O4) nanoparticles functionalized porous biochar (La/Fe-NBC) with high phosphate adsorption properties is synthesized through molten salt pyrolysis-coprecipitation-hydrothermal multi-step regulation, and further reveal the related processes and mechanisms. La(CO3)OH functions as active sites for phosphate adsorption, Fe3O4 imparts magnetic properties to the composite substance, also porous biochar (NBC) acts as the carrier to prevent the agglomeration of La(CO3)OH and Fe3O4 nanoparticles. The adsorption process of La/Fe-NBC for phosphate fits to the Pseudo-Second Order and Langmuir model, with the theoretical maximum adsorption capacity up to 99.46 mg P/g. And La/Fe-NBC possesses excellent magnetic field (14.50 emu/g), stability, and selectivity, which enables for efficient multiple recovery and reuse. Mechanistic studies have shown that ligand exchange (inner-sphere complexation) between phosphate and carbonate/hydroxyl groups of La(CO3)OH, and electrostatic attraction play the dominant roles during adsorption process, although susceptible to the solution pH. While co-precipitation is not influenced of pH conditions but with limited contribution to phosphate adsorption. This study may facilitate to optimize the synthesis design of phosphate multi-functional composites for low-carbon and sustainable treatment of industrial phosphate-containing wastes.

Carbon-based adsorbents as proficient tools for the removal of heavy metals from aqueous solution: A state of art-review emphasizing recent progress and prospects.

Carbon-centric adsorbents (CCA) are diverse forms, from simple biochar (BC) to graphene derivatives, carbon nanotubes (CNTs), and activated carbon (AC), which have been vastly explored for their removal of a plethora of pollutants, including heavy metals (HM). The prominent features of CCA are their operational attributes like extensive surface area, the occurrence of flexible surface functional groups, etc. This work offers a comprehensive examination of contemporary research on CCA for their superior metal removal aptitude and performances in simulated solutions and wastewater flows; via portraying the recent research advances as an outlook on the appliances of CACs for heavy metal adsorption for removal via distinct forms like AC, BC, Graphene oxide (GO), and CNTs. The bibliometric analysis tool was employed to highlight the number of documents, country-wise contribution, and co-occurrence mapping based on the Scopus database. The coverage of research works in this review is limited to the last 5 years (2017-2021) to highlight recent progress and prospects in using CCAs such as AC, BC, GO, and CNTs to remove HM from aqueous media, which makes the review unique. Besides an overview of the common mechanisms of CACs, the future scope of CAC, especially towards HM mitigation, is also discussed in this review. This review endorses that further efforts should be commenced to enhance the repertory of CCAs that effectively eliminate multiple targeted metals in both simulated and real wastewater.

Efficient removal of Cd2+ from aqueous solution with a novel composite of silicon supported nano iron/aluminum/magnesium (hydr)oxides prepared from biotite.

Taking low cost silicate minerals to develop efficient Cd2+ adsorption materials was favorable to the comprehensive utilization of minerals and remediation of environmental pollution. In this study, a composite of silicon supported nano iron/aluminum/magnesium (hydr)oxides was prepared with biotite by combining acid leaching and base precipitation process, which was used to remove Cd2+. Cd2+ adsorption behaviors were in accordance of pseudo-second order kinetic model and Langmuir model, and the obtained maximal Cd2+ adsorption capacity was 78.37 mg/g. Increasing pH and temperature could accelerate the removal of Cd2+. The activation energy was calculated as 66.05 kJ/mol, meaning that Cd2+ removal process was mainly depended on chemical adsorption. XRD and SEM results showed that this composite was a micro-nano structure of layered silica supported nano iron/aluminum/magnesium (hydr)oxides. Cd2+ removal mechanisms were consisted of surface complexation and ion exchange between Cd2+ and other metal ions, and the ion exchange interaction played the major role. These results indicated that a novel efficient utilization way for silicate minerals was developed.

Insights into mechanisms governing the passive removal of inorganic contaminants from acid mine drainage using permeable reactive barrier.

The permeable reactive barrier has been deemed as the most prudent and pragmatic way to passively manage and remediate acid mine drainage (AMD). Herein, insights into mechanisms governing the removal of inorganic contaminants from AMD using a permeable reactive barrier (PRB), i.e. pervious concrete, were reported. In particular, the effects of varying dosages, i.e., 6, 10, 30, and 60 g, of cementitious materials comprising CEM I 52.5R with or without fly ash, hydrated lime, and gypsum were evaluated whilst the fate of chemical species was underpinned using the state-of-the-art analytical techniques, along with PHREEQC geochemical modelling. The role of gypsum, a product formed from the interaction of PRB with AMD in heavy metals attenuation was also elucidated. Findings revealed cementitious materials to play an indispensable role in the removal of inorganic contaminants from AMD. Furthermore, alkalinity from used materials increases the pH (i.e. pH ≥ 12.5) of AMD leading to the precipitation of chemical species. Specifically, the efficacy registered the following sequence: Lime ≥ CEM I ≥ 30%FA ≥ Gypsum with ≥99 for Al and Fe except for Gypsum which attained ≥98 while the performance for Zn removal registered the following sequence, 97 ≥ 98 ≥ 88.8 ≥ 45% for CEM I ≥ Lime ≥30%FA ≥ Gypsum, respectively. Chemical species exist as divalent, trivalent, oxyanions, and other complexes in solution as predicted by PHREEQC. Moreover, they were removed as metal hydroxides, oxyhydrosulphates, and gypsum hence corroborating findings from XRD, SEM-EDS, and FTIR results. Mechanisms which were responsible for the removal of chemical species were precipitation, adsorption, co-adsorption, co-precipitation, ion exchange, and complexation. Henceforth, this study explicitly demonstrated mechanisms that underpin the removal of inorganic contaminants from AMD using PRB and findings from this study will be used to develop effective PRB for the management of acid mine drainage and the receiving environment.

Constructed wetlands for the removal of pharmaceuticals and personal care products (PPCPs) from wastewater: origin, impacts, treatment methods, and SWOT analysis.

The continuous exposure to pharmaceuticals and personal care products can lead to a series of individual antagonistic and synergistic effects and long-lasting toxicity to humans and aquatic lives. This may also lead to developing antibiotic resistance, teratogenic, carcinogenic, and endocrine-disrupting effects. However, several PPCPs are also considered biologically active for non-target aquatic organisms, such as mosquito fish, goldfish, and the algae Pseudokirchneriella subcapitata. Various physicochemical methods such as ozonation, photolysis, and membrane separation are recognized for the effective removal of PPCPs. However, the high operation and maintenance costs and associated ecological impacts have limited their further use. Constructed wetlands are considered eco-friendly and sustainable for the removal of pharmaceuticals and personal care products together with antibiotic resistance genes. Several mechanisms such as sorption, biodegradation, oxidation, photodegradation, volatilization, and hydrolysis are occurring during the phytoremediation of PPCPs. During these processes, more than 50% of PPCPs can be eliminated through constructed wetlands. They also offer several additional benefits as obtained macrophytic biomass may be used as raw material in pulp and paper industries and a source for second-generation biofuel production. In this study, we have discussed the origin and impacts of PPCPs together with their treatment methods. We have also investigated the strengths, weaknesses, opportunities, and threats associated with constructed wetlands during the treatment of wastewater laden with pharmaceutical and personal care products.

Electrocoagulation technology for water purification: An update review on reactor design and some newly concerned pollutants removal.

Water shortage and quality deterioration are plaguing people all over the world. Providing sustainable and affordable treatment solutions to these problems is a need of the hour. Electrocoagulation (EC) technology is a burgeoning alternative for effective water treatment, which offers the virtues such as compact equipment, easy operation, and low sludge production. Compared to other water purification technologies, EC shows excellent removal efficacy for a wide range of contaminants in water and has great potential for addressing limitations of conventional water purification technologies. This review summarizes the latest development of principle, characteristics, and reactor design of EC. The design of key parameters including reactor shape, power supply type, current density, as well as electrode configuration is further elaborated. In particular, typical water treatment systems powered by renewable energy (solar photovoltaic and wind turbine systems) are proposed. Further, this review provides an overview on expanded application of EC in the removal of some newly concerned pollutants in recent years, including arsenite, perfluorinated compounds, pharmaceuticals, oil, bacteria, and viruses. The removal efficiency and mechanisms of these pollutants are also discussed. Finally, future research trend and focus are further recommended. This review can bridge the large knowledge gap for the EC application that is beneficial for environmental researchers and engineers.

Preparation and characterization of boron-doped corn straw biochar: Fe (â ¡) removal equilibrium and kinetics.

Nowadays, iron ions as a ubiquitous heavy metal pollutant are gradually concerned and the convenient and quick removal of excessive iron ions in groundwater has become a major challenge for the safety of drinking water. In this study, boron-doped biochar (B-BC) was successfully prepared at various preparation conditions with the addition of boric acid. The as-prepared material has a more developed pore structure and a larger specific surface area (up to 897.97 m²/g). A series of characterization results shows that boric acid effectively activates biochar, and boron atoms are successfully doped on biochar. Compared with the ratio of raw materials, the pyrolysis temperature has a greater influence on the amount of boron doping. Based on Langmuir model, the maximum adsorption capacity of 800B-BC1:2 at 25 °C, 40 °C, 55 °C are 50.02 mg/g, 95.09 mg/g, 132.78 mg/g, respectively. Pseudo-second-order kinetic model can better describe the adsorption process, the adsorption process is mainly chemical adsorption. Chemical complexation, ions exchange, and co-precipitation may be the main mechanisms for Fe2+ removal.

Amoxicillin removal by pre-denitrification membrane bioreactor (A/O-MBR): Performance evaluation, degradation by-products, and antibiotic resistant bacteria.

Membrane bioreactors (MBRs) are one of the treatment technologies with the potential to remove emerging compounds from wastewater. The present work evaluated the efficiency of an MBR pilot system in removing amoxicillin from synthetic wastewater using a continuous flow pre-denitrification MBR (A/O-MBR) pilot unit. The system operated in three phases: (1) synthetic wastewater and hydraulic retention time (HRT) of 40 h; (2) adding amoxicillin 100 µg L-1 to the influent, and (3) varying flowrate to HRT of 20 h. Liquid chromatography coupled to high resolution mass spectrometry analysis confirmed the presence of five amoxicillin degradation by-products in the effluent. The addition of amoxicillin did not affect chemical oxygen demand (COD) or dissolved organic carbon (DOC) removal efficiencies. Respirometry showed that amoxicillin level did not inhibit heterotrophic bacteria metabolism. The change in HRT reduced the DOC removal (from 84% to 66%) but did not influence COD (>94%) or total nitrogen (>72%). The amoxicillin and by-products removal decreased from 80% to 54% with HRT change. Adsorption and biodegradation represented the largest removed fraction of the antibiotic in the A/O-MBR system (68%). Ecotoxicity assays showed P. fluorescens was more resistant and E. coli less resistant to amoxicillin residues at effluent sample matrix.

Efficiency and mechanisms of cadmium removal via core-shell zeolite/Zn-layer double hydroxides.

To investigate the removal mechanisms of cadmium (Cd) by Zn-layer double hydroxides-modified zeolites substrates in constructed rapid infiltration systems (CRIS), the ZnAl-LDHs and ZnFe-LDHs were synthesized and in-situ coated on the original zeolites through co-precipitation method. The prepared Zn-LDHs-modified and original zeolites were characterized by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) methods, whose results provided the evidences that the Zn-LDHs were successfully coated on the original zeolites. From the results of purification experiments, the average Cd removal rates of ZnAl-LDHs-modified, ZnFe-LDHs-modified and original zeolites were 88.40, 86.00 and 32.52%, respectively; demonstrating that the removal rates of zeolites could significantly improve. Additionally, the modification of Zn-LDHS could enhance the theoretical adsorption ability. According to the results of isothermal adsorption and desorption tests, the desorption rates of Zn-LDHs-modified zeolites were higher than that of original zeolites. Cd adsorption capacity of ZnFe-LDHs-modified zeolites was 1428.57 mg kg-1 and original zeolites was 434.783 mg kg-1. In the adsorption kinetic studies, the pseudo-second-order models were used to well describe the experimental results of Zn-LDHs-modified zeolites, indicating that their adsorption types were attributed to be more stable chemisorption. Besides, the relevant microbial tests also confirmed that microbial enzymatic activity and extracellular polymeric substances (EPS) were significantly promoted on surface of Zn-LDHs-modified zeolites. The contents of EPS on the surface of zeolites were as following: ZnAl-LDHs-modified zeolites (78.58128 µg/g) > ZnFe-LDHs-modified zeolites (71.85445 µg/g) > original zeolites (68.69904 µg/g). Meanwhile, the results of high-throughput sequencing showed that modification by Zn-LDHs improved microbial diversity and relative abundance. The Proteobacteria was the dominant phylum and the Acidobacteria was conducive to Cd removal. Overall, it could be concluded that ZnAl-LDHs-modified zeolites might be applied as an efficient substrate for Cd removal in CRIS.

Pilot-scale hybrid constructed wetlands for the treatment of cooling tower water prior to its desalination and reuse.

Cooling towers are responsible for a large part of the industrial fresh water withdrawal, and the reuse of cooling tower water (CTW) effluents can strongly lower industrial fresh water footprints. CTW requires desalination prior to being reused, but various CTW components, such as total organic carbon (TOC), conditioning chemicals and total suspended solids (TSS) hamper physico-chemical desalination technologies and need to be removed from the CTW. A cost-efficient and robust pre-treatment is thus required, which can be provided by constructed wetlands (CWs). The present study is the first study that determined the CTW pre-treatment efficiency of hybrid-CWs and the impact of winter season and biocides in the CTW on the pre-treatment efficiency. The most efficient CW flow type and dominant removal mechanisms for CW components hampering physico-chemical desalination were determined. Subsurface flow CWs removed PO43-, TSS and TOC as a result of adsorption and filtration. Vertical subsurface flow CWs (VSSF-CW) excelled in the removal of benzotriazole as a result of aerobic biodegradation. Horizontal subsurface flow CWs (HSSF-CW) allowed the denitrification of NO3- due to their anaerobic conditions. Open water CWs (OW-CWs) did not contribute to the removal of components that hamper physico-chemical desalination technologies, but do provide water storage options and habitat. The biological removal processes in the different CW flow types were negatively impacted by the winter season, but were not impacted by concentrations of the biocides glutaraldehyde and DBNPA that are relevant in practice. For optimal pre-treatment, a hybrid-CW, consisting of an initial VSSF-CW followed by an OW-CW and HSSF-CW is recommended. Future research should focus on integrating the hybrid-CW with a desalination technology, e.g. reverse osmosis, electrodialysis or capacitive ionization, to produce water that meets the requirements for use as cooling water and allow the reuse of CTW in the cooling tower itself.

Enhanced nitrate reduction in water by a combined bio-electrochemical system of microbial fuel cells and submerged aquatic plant Ceratophyllum demersum.

High nitrate (NO3-) loading in water bodies is a crucial factor inducing the eutrophication of lakes. We tried to enhance NO3- reduction in overlying water by coupling sediment microbial fuel cells (SMFCs) with submerged aquatic plant Ceratophyllum demersum. A comparative study was conducted by setting four treatments: open-circuit SMFC (Control), closed-circuit SMFC (SMFC-c), open-circuit SMFC with C. demersum (Plant), and closed-circuit SMFC with C. demersum (P-SMFC-c). The electrochemical parameters were documented to illustrate the bio-electrochemical characteristics of SMFC-c and P-SMFC-c. Removal pathways of NO3- in different treatments were studied by adding quantitative 15NO3- to water column. The results showed that the cathodic reaction in SMFC-c was mainly catalyzed by aerobic organisms attached on the cathode, including algae, Pseudomonas, Bacillus, and Albidiferax. The oxygen secreted by plants significantly improved the power generation of SMFC-c. Both electrogenesis and plants enhanced the complete removal of NO3- from the sediment-water system. The complete removal rates of added 15N increased by 17.6% and 10.2% for SMFC-c and plant, respectively, when compared with control at the end of experiment. The electrochemical/heterotrophic and aerobic denitrification on cathodes mainly drove the higher reduction of NO3- in SMFC-c and plant, respectively. The coexistence of electrogenesis and plants further increased the complete removal of NO3- with a rate of 23.1%. The heterotrophic and aerobic denitrifications were simultaneously promoted with a highest abundance of Flavobacterium, Bacillus, Geobacter, Pseudomonas, Rhodobacter, and Arenimonas on the cathode.

Microalgal-bacterial consortia for the treatment of livestock wastewater: Removal of pollutants, interaction mechanisms, influencing factors, and prospects for application.

The livestock sector is responsible for a significant amount of wastewater globally. The microalgal-bacterial consortium (MBC) treatment has gained increasing attention as it is able to eliminate pollutants to yield value-added microalgal products. This review offers a critical discussion of the source of pollutants from livestock wastewater and the environmental impact of these pollutants. It also discusses the interactions between microalgae and bacteria in treatment systems and natural habitats in detail. The effects on MBC on the removal of various pollutants (conventional and emerging) are highlighted, focusing specifically on analysis of the removal mechanisms. Notably, the various influencing factors are classified into internal, external, and operating factors, and the mutual feedback relationships between them and the target (removal efficiency and biomass) have been thoroughly analysed. Finally, a wastewater recycling treatment model based on MBC is proposed for the construction of a green livestock farm, and the application value of various microalgal products has been analysed. The overall aim was to indicate that the use of MBC can provide cost-effective and eco-friendly approaches for the treatment of livestock wastewater, thereby advancing the path toward a promising microalgal-bacterial-based technology.