Wastewater Treatment Research Articles

Research progress of simultaneous nitrogen and phosphorus removal adsorbents in wastewater treatment

Research progress of simultaneous nitrogen and phosphorus removal adsorbents in wastewater treatment

Implementing Differential Recovery Corrections Enhances Accuracy of Mass Balances on Microplastics in Wastewater Treatment

This study examined the impact of using different analytical recovery practices to correct MP concentrations on the performance of count and mass balances of primary wastewater settling. Spiking tests using standard MPs were conducted to evaluate the influence of MP size and sample type on recovery. The derived recovery values were then used to correct MP concentrations and loads in a full-scale primary treatment facility. The results reveal substantial differences in recovery that were dependent upon MP size and sample type, underlining the necessity of incorporating these discrepancies when estimating MP concentrations. Omitting recovery considerations during MP concentration reporting led to underestimations of approximately 40%. In contrast, incorporating MP size and sample type during recovery calculations fostered a more accurate representation of MP concentrations, thereby enhancing the closure of balance models. While a count balance model was not apparently improved through the use differential recovery, the mass balance model showed a significant improvement in closure, reducing the lack of balance from 30.2% to 17.2%. This discrepancy was primarily attributed to the differing proportions of the primary sludge stream load in each model. These findings highlight the importance of incorporating differential recovery into mass balance models and demonstrate the complementary nature of count and mass balance approaches in understanding the fate and transport of MPs in WWTPs. The results of this study have significant implications for improving environmental assessments, policies and engineering design of wastewater treatment processes.

Synergistic flocculation performance and underlying mechanisms of a novel bioflocculant flocan with coagulant iron salt

Flocculation is an integral part of wastewater treatment units and various flocculants have been employed to strengthen the flocs formation and produce clean water. Natural polysaccharides have been employed as eco-friendly bioflocculants for the treatment of turbid water. In the study, flocan is a named exopolysaccharide (EPS) isolated from a coastal mudflat with a high yield of 8.3g/L. Flocan consisted of glucose, mannose, galactose, and glucuronic acid in a molar ratio of 2:3:1:1, along with pyruvate modifications. As the bioflocculant agent, flocan exhibited more than 85% removal efficiency in kaolin suspension in terms of a concentration of 10mg/L at pH 3. The addition of iron salts with flocan showed high flocculation efficiency in acidic kaolin suspension (99.37%) and acidic coal wastewater (99.44%). The carboxyl/hydroxyl groups and branched structure of flocan provided ionic interactions and promoted higher bridging between bioflocculants and negatively charged particles. Coagulants FeCl3 enhanced the flocculating activity via neutralizing and stabilizing the residual negative charge of functional groups. Treatment with EDTA decreased the ionic interactions and reversed the flocculation significantly. Compared with the current bioflocculants, the superior production, low dosage, and excellent flocculating activity implied that flocan showed great potential in acidic wastewater treatment industrially. The coagulants/bioflocculants combination appears to be a promising and sustainable technology for wastewater flocculation.

Modified gum ghatti based hybrid hydrogel nanocomposite as adsorbent material for dye removal from wastewater

A hybrid hydrogel nanocomposite based on the polysaccharide-gum ghatti, has been made and evaluated as an adsorbent material for wastewater treatment. The nanocomposite is composed of a network of gum ghatti-graft-poly(2-acrylamido-2-methylpropane sulfonic acid) with magnetite nanoparticles embedded within. This functional material Ggh-g-PAMPS/Fe3O4 has been characterized by FTIR, TGA, SEM, EDS, XRD, BET and VSM techniques. The presence of magnetite nanoparticles imparted superparamagnetic property to the adsorbent material enabling its easy separation after use with an external magnet. The characterization data indicated mesoporous nature of the nanocomposite adsorbent with mean pore diameter of 4.9 nm. The nanoparticles imparted high surface area to the adsorbent material the value being 4.7 m2g−1 based on nitrogen adsorption experiments. The suitability of the material as an adsorbent for removal of cationic dyes from water was checked with two cationic dyes namely, rhodamine 6G and methylene blue. The maximum adsorption capacity of the nanocomposite Ggh-g-PAMPS/Fe3O4 towards rhodamine 6G and methylene blue were observed to be 403.2 and 427.8 mg g−1 respectively from their individual solutions of concentration 500 mg L−1. The pH dependence on swelling and surface charge indicated medium of pH of 7.0 as the ideal condition for effective adsorption. Freundlich isotherm model and pseudo second order kinetic model are observed to be the most befitting models to describe adsorption. Further, the thermodynamic studies revealed the adsorption to be a spontaneous and endothermic process. The desorption study portrayed the reusability of the adsorbent material. The excellent adsorption performance and magnetic nature of the developed nanocomposite suggests its potential application as an adsorbent material in wastewater treatment.

A review of carbon dots in synthesis strategies, photoluminescence mechanisms, and applications in wastewater treatment

A review of carbon dots in synthesis strategies, photoluminescence mechanisms, and applications in wastewater treatment

Study on substrates purification effect and microbial community structure of vertical subsurface flow constructed wetland under siphon effect

To explore the pollutants removal effects of siphon composite vertical flow constructed wetlands (Sc-VSsFCW), alongside the characteristics of microbial communities and the varying trends of extracellular polymeric substances (EPS) content across substrate layers. Two kinds of distinct Sc-VSsFCW, with loess sphere and clay ceramic grain as substrate materials, respectively, were established. During the experiment, water quality of influent and effluent were detected to investigate system pollutant removal efficiency, routine index detection, microbial diversity analysis and EPS content determination, and substrates were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results indicated that both substrate systems exhibited good pollutant removal effect, with the average removal rate of 90 % for ammonia nitrogen (NH4+-N), and chemical oxygen demand (COD) removal rate within the range of 60–70 %. The long-term re‑oxygenation process inherent in the system successfully augmented the dissolved oxygen (DO) content within the wastewater, and facilitate relative high abundance of Nakamurella, Bacillus, and Nitrospira in these two substrate systems, which enhanced organic matter degradation and nitrification processes. Moreover, the hydraulic conductivity and EPS content in both substrate systems displayed a declining trend, suggesting that the system's unique hydraulic conditions strategies effectively mitigated EPS accumulation and diminished the likelihood of biological clogging. Consequently, the system's distinctive re‑oxygenation and siphon drainage methods boast advantages over traditional vertical flow constructed wetlands in terms of enhancing dissolved oxygen levels and mitigating the risk of biological clogging. This study contributes theoretical underpinnings for the application of constructed wetlands in wastewater treatment and clogging mitigation.

Three birds with one stone: Preparation of multifunctional Fe-MOF/PAN nanofiber membranes for wastewater treatment

In this research, a new NH2-MIL-88B(Fe)/polyacrylonitrile nanofiber membrane (NPNFM) was synthesized utilizing a straightforward electrospinning technique. The morphological characteristics and performance of nanofiber membranes were finely tuned via adjusting the dosage of NH2-MIL-88B(Fe) (NM88B, the “stone”). The prepared NPNFM exhibits superhydrophilicity/underwater superoleophobicity, coupled with outstanding photo-Fenton self-cleaning ability (the first two “birds”). This membrane efficiently and swiftly facilitated the separation of various surfactant-stabilized emulsions under gravitational force, achieving a separation efficiency and flux of up to 99.5 % and 350.3 L m-2h−1, respectively. The fouling on the membrane surface can be rapidly decomposed, attributing to the superior photo-Fenton activity of NM88B. Furthermore, the organic dye methylene blue (MB) was degraded by 97.4 % within 40 min under the catalytic influence of the membrane. The nanofiber membrane has good mechanical properties and its tensile strength is about 2.3 times that of the original membrane attributing to the good compatibility between NM88B and the membrane matrix (the third “bird”). This study proposed new Fe-MOF-based photo-Fenton multifunctional membranes with the characteristics of environmental stability and high efficiency in wastewater treatment fields.

The synergistic effect of Co atomic clusters and single atoms facilitates the fenton-like reaction on A- and R-TiO2

The regulation of single atom (SA) sites is crucial for the promotion of advanced oxidation processes (AOPs). Here A- and R-TiO2 with Co mixed sites (clusters and single atoms, CS) were prepared to degrade sulfamethoxazole (SMX) by activating peroxymonosulfate (PMS). Co CS/A-TiO2+PMS system can completely remove SMX within 14 min under secondary effluent and dark conditions, and its rate constant (0.4926 min-1) was 4.4, 3.2 and 2.5 times higher than that of Co SA/R-TiO2, Co SA/A-TiO2 and Co CS/R-TiO2 systems, respectively. Experiments and calculations verified that the electron configuration of Co SA was optimized by Co clusters, facilitating the adsorption, conversion and desorption of PMS by Co SA, leading to the enhancement of Fenton-like activity. Co CS/A-TiO2 catalytic sponges exhibited exceptional degradation performance in microreactor treatment experiment. This work reveals the synergistic effect between SA and clusters at atomic level and provides an all-purpose strategy (catalytic sponge) for the recovery of non-magnetic catalysts in wastewater treatment.

High-salt-resistance aerogels composed of chitosan and anode powder for effective solar interfacial evaporation

Solar interfacial evaporation technology is widely utilized for seawater desalination and wastewater treatment, which are currently areas of significant research interest. The primary factors to consider when transitioning the evaporator from laboratory settings to practical applications are its mechanical stability and resistance to salt. In the present study, composite aerogels consisting of an anode powder (AP), polypyrrole (Ppy), and chitosan (CS) were produced by a conventional technique involving physical cross-linking and in situ growth. The resulting aerogel has a compact pore structure that enhances the scattering of light on its surface and increases the area available for evaporation. As a result, the material exhibits exceptional photothermal capabilities, with water evaporation rates and photothermal conversion efficiencies of 1.865 kg m−2 h−1 and 85.96%, respectively, when exposed to 1 sun illumination. Simultaneously, the aerogel exhibits exceptional efficacy in water purification and resistance to salt when employed for the treatment of heavy-metal wastewater, seawater, and highly concentrated saline solutions. Furthermore, the utilization of AP as a light-absorbing substance aligns with the principles of green chemistry by promoting the recycling and repurposing of waste materials. These results provide novel insights into the potential applications of lithium battery waste and the optimization of solar-interfacial-evaporator design.

Utilization of Ziziphus spina-christi leaf extract-loaded chitosan nanoparticles in wastewater treatment and their impact on animal health

Ziziphus leaf extract (ZEX), chitosan nanoparticles (CS NPs) and Ziziphus leaf extract loaded chitosan nanoparticles (ZEX-CS NPs) were prepared in this study and after chemical analysis and characterization, they were used in wastewater purification. The study also aimed to establish, using an animal model, the feasibility of employing treated water in drinking applications. ZEX-CS NPs were prepared by ionic gelation method. About 25 male Sprague Dawley rats (10 weeks and 170-200 g) were divided into five groups (5 rats/group): group I received tape water; group II received untreated wastewater, group III received ZEX treated wastewater, group IV received CS NPs treated wastewater and group V received ZEX-CS NPs treated wastewater. ZEX-CS NPs have a size of 73 nm, hydrodynamic size of 85.81 nm and zeta potential of −33.68 mV. In addition, ZEX-CS NPs have stronger antioxidant and anti-inflammatory activity with moderate anti-coagulant activity and weaker cytotoxicity than ZEX and CS NPs. Group II showed a significant elevation in the kidney function parameters, oxidative stress and cytokine levels when compared to the other groups, in addition; no significant differences were found in all measured parameters between the rats of group I and V. ZEX-CS NPs were effective in wastewater purification.

Non-wood Plants as Sources of Cellulose for Paper and Biodegradable Composite Materials: An Updated Review

Background: Non-wood plant parts provide unique opportunities for cellulose for paper manufacture and offer advantages over wood, such as less harsh chemicals and lower lignin content. Objective: This review examined several cellulose extraction procedures from non-wood sources, such as leaves, stems, grass, straw, fruit peels, and husks. Methods: Acid and alkali extraction, oxidation, and bleaching were the main techniques used. Corresponding mechanical properties of cellulose derivatives were also reviewed, with tensile strength being the most reported property, with variability among the species and products. Additives were also explored to improve the properties of non-wood paper. Results: Further processing of cellulose into nanocrystalline cellulose enabled the manufacture of biodegradable composites with a wide range of utilities in wastewater treatment, reinforcing materials, alternatives to plastics and circuit boards for nanotechnology applications. Various methods now available for cellulose extraction provide scientists with several efficient options for different plant materials with beneficial properties. Conclusion: Non-wood cellulose has found its uses in several industries, but further research may consolidate these attempts.

Sustainable valorization of agricultural waste into bioplastic and its end-of-life recyclability for biochar production: Economic profitability and life cycle assessment

While the industrial sectors have recently focused on producing bioplastic materials, the utilization of edible feedstocks and the generation of wastes and byproducts during the bioplastic synthesis process might delay achieving the environmental sustainability strategy. To overcome these limitations related to bioplastic industrialization, this study focuses on synthesizing bioplastics from waste sources, followed by recycling its end-of-life (e.g., spent and exhausted) material into biochar. Sweet potato peel waste, banana pseudo-stems, and cooking oil waste were used to extract starch, cellulose, and glycerol (a plasticizer) involved in bioplastic manufacturing, respectively. It was found that the cellulose content of 30% w w–1 in bioplastic maintained the best physicochemical, mechanical, and biodegradability properties, recommending a high applicability for food packaging. The exhausted bioplastic was then pyrolyzed to maintain a biochar yield of 32.60±0.89%, avoiding the risk of secondary pollution from waste material disposal. This biochar was utilized to treat wastewater generated from the bioplastic synthesis process, showing the optimum adsorption factors of biochar dosage= 3.81 g L–1, time= 102 min, and solution pH= 7.81. The combined bioplastic production, waste pyrolysis, and wastewater treatment scheme could earn profits from biomaterial sales, carbon credit, and pollution reduction shadow price, maintaining a 6.78-year payback period and a 12.09% internal rate of return. This integrated framework depicted better contributions to the mid-point/end-point life cycle assessment impact categories than the only bioplastic production scenario. This study contributed towards achieving several sustainable development goals (SDGs), including SDG#3: human health protection, SDG#6: wastewater treatment, and SDG#12: waste recycling.

Enhanced removal of Cr(VI) from aqueous solutions using a zero-valent nickel/iron-PDA@PVDF membrane prepared via a simple blending method

Nano zero-valent iron (nZVI) is extensively employed in the realm of wastewater treatment. However, conventional synthesis methods involve inherent risks of nZVI oxidation and aggregation, resulting in challenging recovery and potential waste generation. To address these concerns and improve stability, nano zero-valent nickel (nZVNi) was employed as a modifier for nZVI. The modified nZVNi/nZVI was successfully blended with polydopamine (PDA)-modified polyvinylidene fluoride (PVDF) powder, enabling the preparation of a novel hydrophilic composite membrane termed nZVNi/nZVI-PDA@PVDF (NFPP). PDA played a crucial role in effectively immobilizing nZVI particles and preventing their oxidation and aggregation. Scanning electron microscopy was used to confirm the consistent dispersion of nZVNi/nZVI particles both on the surface of the membrane and within its pores. Moreover, the NFPP membrane exhibited excellent performance in removing Cr(VI), with a maximum adsorption capacity of 75.65 mg/g. The presence of PDA endowed the NFPP membrane with a plentiful supply of hydroxyl and amino groups, enhancing its hydrophilicity, antioxidation properties, and loading capacity for nZVNi/nZVI. Additionally, the NFPP membrane demonstrated remarkable resistance to interference under different pH and ionic conditions. The removal of Cr(VI) by the NFPP membrane followed a pseudo-second-order kinetics and Langmuir isotherm adsorption model. Furthermore, the NFPP membrane retained good performance and stability in Cr(VI) removal even after undergoing five cycles. This study indicates that the highly efficient NFPP composite material holds promising potential for application as a functional material in heavy metal wastewater treatment.

Viral load-dependent masking effect by activated sludge during the aeration process

Emission of bioaerosols from wastewater treatment processes is a significant risk for the workers involved and the residents around, but the driving factors of viral aerosol emission and are not clear. In this study, four model viruses (Phi6, MS2, PhiX174, and T7) were used to investigate the effects of activated sludge on the emission of viral aerosols. It was found that more than 95% of the viruses could be adsorbed by the activated sludge within three hours. During aeration, when the activated sludge was present, the virus-containing aerosols became larger compared to no sludge situation. This implies that some viruses were adsorbed by the sludge particles during the aerosolization. The viral aerosol concentrations in air were proportion to the virus concentrations in the sludge-free wastewater, but much lower when aerosolized from the sludge suspension. This result showed a masking effect by the sludge. However, the masking effect was gradually weakened or even disappeared, when the spiked virus concentrations were less than 107 copies/mL, which are much closer to the presence of pathogenic viruses in the real wastewater. One possible explanation could be that small sludge particles might adsorb viruses preferentially compared to large ones and could help the aerosolization of viruses. This was demonstrated by the increased emission of viral aerosols after reducing the particle size of the activated sludge by sonication. This work reveals evidence that the sludge will actually not mask the aerosolization of pathogenic viruses in the wastewater treatment plant as the concentrations of most viruses are very low, and health risks always exist.

Self-enhanced photoelectrocatalytic removal of Ni-organic complex and Ni recovery by the in-situ forming anodic Ni deposit: P-n junction-driven photocatalytic oxidation and chemical oxidation

The aim of this study was to propose a novel strategy for self-enhanced Ni-organic complex decomplexation and simultaneous Ni recovery based on photoanodic Ni deposition using photoelectrocatalytic (PEC) system. Compared to the conventional PEC process, the deposition of Ni2+ on TiO2 nanorod arrays photoanode led to a 30 % increase in decomplexation efficiency for Ni-ethylenediaminetetraacetic acid (Ni-EDTA). The Ni-EDTA removal rate reached 81.0 ± 0.9 %, and the Ni recovery rate achieved 58.2 ± 0.1 % under a bicarbonate buffer condition at pH 8.5 and a current density of 0.5 mA/cm2. The anodic high-valent Ni deposit can mediate chemical oxidation of Ni-EDTA in the PEC process, which has significant potential for deep mineralization of Ni-EDTA. The formation of Ni-deposited TiO2 film significantly improved PEC activity of photoanode, as revealed by the facilitated interfacial charge transfer, suppressed charge recombination, and improved light harvesting capacity. Moreover, the photocatalytic film that exhibited p-n heterojunction characteristics associated with the accelerated electron-hole pair separation and downward shift in energy bands of TiO2, stimulated ‧OH generation during PEC process, playing a pivotal role in Ni-EDTA decomplexation. Our results highlight the potential of using anodic Ni deposition for the efficient PEC treatment of plating wastewater containing Ni-organic complex.

Enhanced hydrolytic acidification with Zero-Valent Iron for efficient treatment of comprehensive wastewater from industrial parks: mechanistic insights and toxicity reduction

In this study, a laboratory-scale zero-valent iron (ZVI)-enhanced hydrolytic acidification system was established to treat the comprehensive wastewater from Nanjing Jiangbei New Material Science Technology Park. Results indicated that the ZVI-enhanced hydrolytic acidification system achieved a maximum COD removal efficiency of 95.0%, surpassing the performance of the system without ZVI by 12.2%. Microbial community analysis revealed the enrichment of electrogenic bacterium Bacteroidetes_vadinHA17 and typical hydrogenotrophic methanogen Methanobacterium due to ZVI addition. High-throughput sequencing combined with PICRUSt2 analysis demonstrated acetate production was promoted, and butyrate and propionate production was inhibited. Additionally, Oxygen Uptake Rate-based toxicity assays revealed the hydrolytic acidification system transitioned the wastewater of three enterprises from low toxicity to non-toxic status and two from high to low toxicity. While the ZVI-enhanced hydrolytic acidification system successfully reduced the toxicity of all highly and low toxic wastewaters to non-toxic levels.

Biochar-bacteria coupling system enhanced the bioremediation of phenol wastewater-based on life cycle assessment and environmental safety analysis

The efficient treatment of phenol wastewater is of great necessity since it induces serious pollution of water and soil ecosystems. Using biochar-immobilized functional microorganisms can innovatively and sustainably deal with the existing problem. In this study, we utilized response surface methodology (RSM) combined with life cycle assessment (LCA) to improve phenol biodegradation rate through a novel separated alkali-resistant and thermophilic strain Bacillus halotolerans ACY. Bioinformatic analysis revealed the genetic foundation of ACY to adapt to harsh environments. The characteristics of pig manure biochar (PMB) produced at varying pyrolysis temperatures (300-700 ℃) and adsorption experiment were investigated, immobilization of the phenol-degrading ACY on PMB600 under alkaline and high pollution load promoted phenol removal and extreme environment resistance, and the phenol removal rate reached 99.5% in 7d in actual phenol wastewater, which increased compared with those achieved by PMB (50.6%) and free bacteria (80.5%) alone. Scanning Electron Microscope (SEM) and Fourier transform infrared spectrometry (FTIR) observations indicated the successful bacterial immobilization on PMB600. Reusability and economic cost study further demonstrated PMB600 as an excellent carrier for wastewater treatment. LC-MS, toxicology and carbon footprint analyses demonstrated that bacterial metabolism exerted synergy with adsorption for phenol removal, while biodegradation exerted the predominant impact on the immobilized bacterial system. This study provides an eco-friendly and effective approach to treat phenol wastewater.

Wastewater treatment plants circular performance models evaluation: Portugal case-study

Population growth, economic growth, and changes in societal habits have led to significant changes in resource consumption. Therefore, it's crucial to accelerate the “reduce, reuse, recycle, and recover” of resources to ensure the balance of ecosystems, and water is surely one of the most fundamental resources. The acceleration of this approach in the water cycle makes sense only if we combine a circular economy (CE) transition with a sustainable perspective. In this context, more rational usage of water resources (which are under pressure) and more sustainable wastewater practices are expected to be a way towards the CE in the water and wastewater sector. This study provides a description and evaluation of existing frameworks that can be used to measure and assess the level of circularity of the wastewater treatment plant (WWTP). The treatment of urban wastewater requires new concepts of management and operation for the adaptation of existing plants, which lack robustness and flexibility, to face these new challenges and requirements because we can no longer continue to look at the WWTP only as treatment units, but as wastewater resource recovery facilities. This transformation must be transposed according to a matrix that allows the assessment to describe the current situation, analyse the problem, identify vulnerabilities and opportunities, identify, and evaluate measures, and identify and evaluate strategies. Considering that decision-makers face profound uncertainties such as climate change, population growth, population needs, innovative technologies, economic developments, ecosystem preservation and the impacts of human and natural activities.

Facile synthesis of Metal-Organic Framework/Chitosan cryogel as a robust Scavenger for Diclofenac sodium

Diclofenac sodium (DS), a commonly detected contaminant in aquatic environments, poses a a significant risk to both the ecological balance and the safety of aquatic products. Therefore, efficient removal of DS from water is ergently needed but remains a major challenge. In this study, an environmentally friendly Fe-based metal–organic framework/chitosan (NH2-MIL-53(Fe)/CS) cryogel was prepared through a Schiff base condensation reaction under mild conditions. Taking advantage of the catalytic role of the MOF in accelerating the reaction between CS and 1,3,5-triformylphloroglucinol, NH2-MIL-53(Fe) powders were incorporated into the polymeric networks within 30 s. Owing to the rich binding sites, the resulting NH2-MIL-53(Fe)/CS cryogel demonstrated remarkable efficacy in eliminating DS from water. The adsorption process reached equilibrium within 120 min with a maximum adsorption capacity of 728.6 mg g−1. A comprehensive mechanistic investigation revealed that the exceptional adsorption capability of the NH2-MIL-53(Fe)/CS cryogel for DS was attributed to the synergistic effect of multiple interactions, including favorable hydrophilicity, electrostatic forces, π-π stacking, hydrogen bonding, and coordination. Thus, this study provides a straightforward and rapid synthesis route for MOF/CS cryogel, offering a promising adsorbent that combines exceptional adsorption performance with ease of separation. The resulting MOF/CS cryogel holds great potential for the treatment of DS-contaminated wastewater.

Efficiency Evaluation of the Continuous Flow Electrocoagulation Process for the Treatment of Oily-Contaminated Wastewater

Efficiency Evaluation of the Continuous Flow Electrocoagulation Process for the Treatment of Oily-Contaminated Wastewater