Performance Of Constructed Wetlands Research Articles

Nitrate and ammonium removal in constructed wetlands: Experimental insights and zero-dimensional numerical modeling

Constructed wetlands (CWs) have emerged as effective wastewater treatment systems, mimicked natural wetland processes but engineered for enhanced pollutant removal efficiency. Ammonium (NH4+) and nitrate (NO3−) are among common pollutants in wastewater, posing significant environmental and health risks. The primary objective of this study is to compares the performance of CWs using gravel and three sizes of natural pumice, along with phragmites australis, in horizontal and horizontal-vertical CWs for nitrate and ammonium removal in the complementary treatment of domestic wastewater. Additionally, the study aims to develop and validate a numerical model using MATLAB software to predict the removal efficiency of these pollutants, thereby contributing to the optimization of CW design and operation. The model operates as a zero-dimensional model based on the law of mass conservation, treating the wetland as a completely mixed reactor, thus avoiding complexities associated with solute movement in porous media. It accurately could predict removal efficiency of chemical, biochemical, and biological indicators while considering active and passive absorption mechanisms by plant uptake. Notably, the determination of coefficients in the model equation does not rely on potentially error-prone laboratory measurements due to sampling issues. Instead, optimization techniques alongside field data robustly estimate these coefficients, ensuring reliability and practicality. Results indicate that higher pollutant concentrations increase reaction rates, particularly enhancing CW efficiency in ammonium removal. Pumice, especially in larger sizes, exhibits superior absorption due to increased porosity and surface area. Overall, the model accurately predicts nitrates concentrations, demonstrating its potential for CW performance optimization and confirming the significance of effective pollutant removal strategies in wastewater treatment.

Biotic/abiotic transformation mechanisms of phenanthrene in iron-rich constructed wetland under redox fluctuation

Iron-rich constructed wetlands (CWs) could promote phenanthrene bioremediation efficiently through biotic and abiotic pathways, which have gained increasing attention. However, the biotic/abiotic transformation mechanisms of trace organic contaminants in iron-rich CW are still ambiguous. Herein, three CWs (i.e., CW-A: Control; CW-B: Iron-rich CW, CW-C: Iron-rich CW + tidal flow) were constructed to investigate the transformation mechanisms of phenanthrene through Mössbauer spectroscopy and metagenomics. Results demonstrated CW-C achieved the highest phenanthrene removal (94.0 %) and bacterial toxicity reduction (92.1 %) due to the optimized degradation pathway, and subsequently achieved the safe transformation of phenanthrene. Surface-bound/low-crystalline iron regulated hydroxyl radical (·OH) production predominantly, and its utilization was promoted in CW-C, which also improved electron transfer capacity. The enhanced electron transfer capacity led to the enrichment of PAH-degrading microorganisms (e.g., Thauera) and keystone species (Sphingobacteriales bacterium 46–32) in CW-C. Additionally, the abundances of phenanthrene transformation (e.g., EC:1.14.12.-) and tricarboxylic-acid-cycle (e.g., EC:2.3.3.1) enzyme were up-regulated in CW-C. Further analysis indicated that the safe transformation of phenanthrene was mainly attributed to the combined effect of abiotic (·OH and surface-bound/low-crystalline iron) and biotic (microbial community and diversity) mechanisms in CW-C, which contributed similarly. Our study revealed the essential role of active iron in the safe transformation of phenanthrene, and was beneficial for enhanced performance of iron-rich CW.

Bibliometric Analysis of Nitrogen Removal in Constructed Wetlands: Current Trends and Future Research Directions

Nitrogen pollution in water environments has reached critical levels globally, primarily stemming from agricultural runoff, industrial discharges, and untreated sewage. The excessive presence of nitrogen compounds poses a significant threat to water quality, leading to adverse impacts on ecosystems and human health. Reaching a breakthrough in the technology of constructed wetlands (CWs) for mitigating nitrogen pollution is hindered by existing knowledge gaps regarding the mechanisms involved in the removal process. Reaching this understanding, we offer a comprehensive summary of current advancements and theories in this research field. Initially, bibliometric techniques were employed to identify yearly patterns in publications and areas of research focus. Subsequently, the chosen documents underwent statistical analysis using VOSviewer_1.6.20 to determine countries’ annual productivity, significant publication years, influential authors, keyword clustering analysis, and more. Finally, a comprehensive overview is provided on the elimination of nitrogen through CWs, encompassing insights into microbial communities and structure types. This analysis aims to uncover potential strategies for optimizing the rate of nitrogen removal. Furthermore, this study elucidates the current research trend concerning the nitrogen removal performance of CWs and identifies challenges and future research directions in this field.

Occurrence, fate and distribution of emerging organic pollutants in full-scale hybrid constructed wetlands treating municipal effluents

The presence of emerging organic pollutants (EOPs) in municipal wastewater has raised concerns regarding their potential impact on human health and the environment. Constructed wetlands (CWs) have been identified as an effective and environmentally friendly solution for removing EOPs from municipal wastewater at a reasonable cost. This study investigated the performance of a full-scale hybrid constructed wetlands (HCWs) treatment system in reducing a total of 59 different types of EOPs. Findings show that the efficiency of the HCWs system in removing EOPs varied significantly depending on the specific physical and chemical properties of the pollutants. Pharmaceuticals (PhACs), personal care products (PCPs), and endocrine-disrupting chemicals (EDCs) were observed to be more effectively removed compared to bactericides, pesticides, and flame retardants, with removal efficiencies exceeding 54 %. Furthermore, the efficiency of the HCWs system in EOPs removal was observed to be influenced by seasonal variations. Specifically, the removal rate of PhACs in the spring and summer seasons reached 54.08 % ± 3.91 % and 61.04 % ± 8.58 %. The choice of substrate and plant species used within the system exhibited a notable impact on its overall removal efficiency. Moreover, the reduction effectiveness of EOPs across different treatment units varied significantly. Among these units, the bidirectional cross-flow filtration unit demonstrated superior reduction capabilities for PhACs and EDCs, with concentration reductions of 89.62 % and 86.34 %, respectively. Overall, this research emphasizes the importance of considering the specific characteristics of the pollutants and the system components to optimize the performance of CWs for EOPs removal in municipal wastewater.

Influence of vegetation and substrate type on removal of emerging organic contaminants and microbial dynamics in horizontal subsurface constructed wetlands

Constructed wetlands (CWs) offer an efficient alternative technology for removing emerging organic contaminants (EOCs) from wastewater. Optimizing CW performance requires understanding the impact of CW configuration on EOC removal and microbial community dynamics. This study investigated EOC removal and microbial communities in horizontal subsurface flow (HSSF) CWs over a 26-month operational period. Comparison between tuff-filled and gravel-filled CWs highlighted the superior EOC removal in tuff-filled CWs during extended operation, likely caused by the larger surface area of the tuff substrate fostering microbial growth, sorption, and biodegradation. Removal of partially positively charged EOCs, like atenolol (29–98 %) and fexofenadine (21–87 %), remained constant in the different CWs, and was mainly attributed to sorption. In contrast, removal rates for polar non-sorbing compounds, including diclofenac (3–64 %), acyclovir (9–85 %), and artificial sweeteners acesulfame (5–60 %) and saccharin (1–48 %), seemed to increase over time due to enhanced biodegradation. The presence of vegetation and different planting methods (single vs. mixed plantation) had a limited impact, underscoring the dominance of substrate type in the CW performance. Microbial community analysis identified two stages: a startup phase (1–7 months) and a maturation phase (19–26 months). During this transition, highly diverse communities dominated by specific species in the early stages gave way to more evenly distributed and relatively stable communities. Proteobacteria and Bacteroidetes remained dominant throughout. Alphaproteobacteria, Acidobacteria, Planctomycetes, Salinimicrobium, and Sphingomonas were enriched during the maturation phase, potentially serving as bioindicators for EOC removal. In conclusion, this study emphasizes the pivotal role of substrate type and maturation in the removal of EOCs in HSSF CW, considering the complex interplay with EOC physicochemical properties. Insights into microbial community dynamics underscore the importance of taxonomic and functional diversity in assessing CW effectiveness. This knowledge aids in optimizing HSSF CWs for sustainable wastewater treatment, EOC removal, and ecological risk assessment, ultimately contributing to environmental protection.

Toxicity removal from contaminated water by constructed wetlands assessed using multiple biomarkers in human stem cell assays

Constructed wetlands (CWs) have been developed rapidly as a sustainable water treatment technique. However, the capability of CWs for remediating the contaminated water based on toxicity assessment remains largely unknown. Four surface flow CWs and two integrated surface-subsurface flow CWs, from five cities in central and eastern region of China were evaluated, concerning the adverse effects of effluents and the toxicity reduction efficiency. Human bone marrow mesenchymal stem cells (hBMSCs) were employed as a human relevant in vitro model. The influent extractions caused cytotoxicity in a dose-dependent manner. The non-cytotoxic dilutions of the influents enhanced the genotoxicity marker γ-H2AX and reactive oxygen species levels. In addition, the influent repressed the osteogenic and neurogenic differentiation, and stimulated the adipogenic differentiation. Cytotoxicity of the contaminated water was reduced by 54 %–86 % after treatment with CWs. CWs were effective to remove part of the sub-lethal effects, with lower reduction than cytotoxicity. The integrated biomarker response (IBR) value of the effluents from the six CWs is lower than that of four secondary and one tertiary wastewater treatment plants. The IBR of the six CWs influents were in the range of 8.6–10.6, with a reduction of 15–50 % after the pollution restoration in CWs. The two integrated surface-subsurface flow CWs achieved higher IBR removal than the four surface flow CWs, possibly due to improved treatment effects by the combined systems. Cytotoxic and genotoxic effects of polar fractions in the CW effluents were stronger than the medium-polar and the non-polar fractions. Besides, PPARγ agonists present in the effluents played crucial roles and ERα agonists may make modest contributions. The present study enhances understanding of the role of CWs in achieving safe wastewater reclamation and provides evidence for further improving toxicity reduction in CWs performance.

Modified basalt fibers boost performance of constructed wetlands: Comparison between surface coating and chemical grafting

Modified basalt fiber (MBF) is a potential material that has been applied in wastewater treatment fields. In this study, superior performances of MBFs by calcium (Ca-MBF) and polyethyleneimine modification (PEI-MBF) were compared in constructed wetlands (CWs). Via chemical grafting, higher biofilm contents were observed on the surface of PEI-MBF, compared to Ca-MBF. Moreover, MBF increased key enzyme activities particularly in lower substrate layer, contributing to positive responses of microbial community in CWs. For instance, PEI-MBF boosted microbial richness and diversity and improved the abundances of denitrifying functional bacteria and biomarkers like Thauera, Vulcanibacillus, and Maritimimonas, probably promoting nitrate removal compared with Ca-MBF group. By contrast, Ca-MBF enriched more functional genera involved in nutrients removal, with the highest removal of ammonium (43.9 %), total nitrogen (66.2 %), and total phosphorus (37.1 %). Overall, this work provided new findings on improved performance of CWs with MBF.

Nitrogen removal performance and mechanisms of three aquatic plants for farmland tail water purification

Constructed wetlands (CWs) are commonly used to control excessive nitrogen from farmlands; however, the interactions between vegetation and microorganisms, nitrogen removal performance, and the mechanisms involved remain unclear in subtropical areas. This study aimed to investigate the nitrogen removal performance and mechanism of CWs containing Canna indica, Acorus calamus, and Thalia dealbata. The results show that CWs with plants had significantly higher nitrogen removal efficiencies than those without, with those planted with T. dealbata having the highest efficiency. T. dealbata performed better than the other two plants due to its high biomass and excellent nitrogen uptake capacity; more importantly, CWs with it had the highest abundance of nitrogen functional genes. Microbial nitrification-denitrification, the primary process of nitrogen removal in CWs, contributed to 88 %, 91 %, and 84 % of the TN removal in the CWs with C. indica, A. calamus, and T. dealbata, respectively, 29 %–158 % higher than that in CWs without plants. Microorganisms played a crucial role in nitrogen removal in the CWs, while plants significantly stimulated microbial activity by enhancing microbial abundance and creating a suitable environment for growth and metabolism. These results can help in understanding the contribution of plants in cleaning farmland tailwater and further optimization of plant configuration and management strategies in wetland ecosystems to improve nitrogen removal efficiency.

Evaluation of the Performance of Nature-Based Constructed Wetlands for Treating Wastewater from Various Land Uses in Korea

Land use changes, specifically the growth of impervious areas due to urbanization, exacerbate non-point-source pollutants in stormwater runoff, surpassing discharge from point sources in Korea. The application of nature-based solutions, such as constructed wetlands (CWs), is becoming popular for stormwater treatment, but challenges arise when background concentrations are overlooked, leading to reduced pollutant removal efficiency. This study aims to propose a plan for the sustainability of CWs by evaluating design appropriateness and utilizing existing monitoring results. The evaluation of 63 CWs reveals that meteorological factors, specifically antecedent dry days and rainfall depth, have significant impacts on urban stormwater runoff quality in various land uses, affecting the performance of CWs. Designing CWs considering land use is crucial due to the considerable concentration variations across different land uses. Improving CW performance requires proper maintenance strategies to ensure effective pollutant removal mechanisms, especially for poorly degradable organic substances post treatment. Rainfall characteristics play a pivotal role in CW design and operation, affecting capacity, efficiency estimation, and maintenance frequency. Considering various factors such as land use, watershed characteristics, and ease of maintenance is essential when utilizing CWs. This study’s findings contribute to the design and operation of future CWs, emphasizing the need for continuous performance analyses through long-term monitoring.

Opposite response of constructed wetland performance in nitrogen and phosphorus removal to short and long terms of operation

Constructed wetlands (CWs) have been widely used for treating polluted water since the 1950s, with applications in over 50 countries worldwide. Most studies investigating the pollutant removal efficiency of these wetlands have focused on differences among wetland designs, operation strategies, and environmental conditions. However, there still remains a gap in understanding the variation in wetland pollutant removal efficiency over different time scales. Therefore, the main aim of the study is to address this gap by conducting a global meta-analysis to estimate the variation in nitrogen (N) and phosphorus (P) removal by wetland in short- and long-term pollutant treatment. The findings of this study indicated that the total efficiencies of N and P removal increased during short-term wetland operation but decreased during long-term operation. However, for surface flow CWs specifically, the efficiencies of N and P removal increased during short-term operation and remained stable during long-term operation. Moreover, the study discovered that wetland N removal efficiency was influenced by seasons, with an increase in spring and summer and a decrease in autumn and winter. Conversely, there was no significant seasonal effect on P removal efficiency. Additionally, high hydraulic load impaired wetland N and P removal efficiency during long-term operation. This study offers a critical review of the role of wetlands in wastewater treatment and provides valuable reference data for the design and selection of CWs types during wastewater treatment in the aspect of sustainability.

SIGNIFICANCE OF CONSTRUCTED WETLANDS IN COMBATING POLLUTANTS FROM WASTEWATER: A SUSTAINABLE DEVELOPMENT PERSPECTIVE

Water contamination is the greatest hazard to public health. Addressing water scarcity and protecting accessible water sources necessitates the effective treatment of wastewater. This makes the use of sustainable solutions such as constructed wetlands (CWs) essential. CWs leverage natural processes involving wetland vegetation, soils, and microbial communities. This study evaluates the efficiency of a horizontal sub-surface flow CW, established with local plants at Hudiara drain, in removing pollutants such as Biochemical Oxygen Demand (BOD), Turbidity, Nitrates, Phosphates, and pH, across different months. The study reveals that while temperature and precipitation rates influence the CW's efficacy, the linear regression model indicates a strong correlation between phosphorus and BOD levels with precipitation. However, nitrates are sensitive to temperature, and turbidity is influenced by both temperature and precipitation within certain limits. Additional factors impacting CW performance include wastewater characteristics, design flow, and wetland location. When compared with Pakistan Environmental Quality Standards (PEQS), it is concluded that CWs are effective in wastewater treatment. By constructing CWs along the banks of wastewater drains, treated water from the outlet chamber can be collected and redirected, offering a viable solution to water scarcity challenges.

Recent Advances in the Effects of Biochar on Constructed Wetlands: Treatment Performance and Microorganisms

Constructed wetlands (CWs) are a kind of green environmental protection technology, which are widely used in sewage treatment. Traditional CWs are faced with the problem of a low treatment effect of high-concentration sewage. In recent years, biochar, as a new type of adsorption material, has been used in CWs because of its advantages of large specific surface area, strong adsorption capacity, and wide material sources. This paper systematically summarized the characteristics of biochar and the preparation of biochar by studying the changes in microorganisms added to CWs and compared the effects of different treatment methods coupled with biochar on the treatment performance of CWs. The effects of biochar coupled with CWs on enzyme activity, functional genes, metabolites, and microbial communities were investigated. This review summarizes how different preparation methods affect the properties of biochar and how these biochar properties cause changes in the microorganisms added to CWs. It provides a new theoretical basis for the treatment of pollutants in CWs.

Advantages of using a carbon-rich substrate in a constructed wetland for agricultural water treatment: Carbon availability and biota development

Proper bed substrate selection is essential for the growth of microorganisms and plants, which are key elements in constructed wetlands (CWs) performance. This is even more important in CWs that treat irrigated agricultural drainage water characterised by a high nitrogen (N), but low carbon (C) and phosphorus (P) concentration. This nutrient imbalance compromises biota activity and limits water treatment processes. Three substrates were tested in a CW field-scale pilot plant for 2 years: gravel (100%) and two mixed substrates, gravel + 30% natural wetland soil and gravel + 10% biochar. While gravel is one of the most commonly used substrates in subsurface flow CWs, soil has hardly been employed, and field-scale biochar application studies are scarce. We analysed the effect of adding a C-rich substrate to gravel on both nutrient imbalance correction and the biotic performance of CWs. Adding natural soil or biochar increased P availability in beds. However, the dissolved organic C concentration in interstitial water was only enhanced by soil addition. Unlike gravel, microbial density and activity, and Phragmites australis plant growth, were higher in beds with soil, followed by those with biochar. A similar pattern was observed for plant tissue quality. Although biochar proved positive for biota, it had a short-term effect as a source of C and P. Therefore, employing a suitable gravel-soil mixture provides notable advantages for the irrigated agricultural water treatment challenge. Even after considering some limitations, our results represent an important step to design CWs that treat this wastewater type and for eutrophication control in sustainable agroecosystems.

Efficiency and effectiveness of systems for the treatment of domestic wastewater based on subsurface flow constructed wetlands in Jarabacoa, Dominican Republic

Constructed wetlands (CW) are well known nature-based systems for water treatment. This study evaluated the efficiency and effectiveness of seven domestic wastewater treatment systems based on horizontal flow CWs in Jarabacoa, the Dominican Republic. The results showed that the CWs were efficient in reducing the degree of contamination of wastewater to levels below the Dominican wastewater discharge standards for parameters such as the 5-day biochemical oxygen demand (BOD5) and chemical oxygen demand, but not for the removal of phosphorus and fecal coliforms. In addition, a horizontal flow subsurface wetland in the peri-urban area El Dorado was evaluated in terms of the performance of wastewater treatment in tropical climatic conditions. The concentrations of heavy metals, such as zinc, copper, chromium, and iron, were found to decrease in the effluent of the wetland, and the concentrations for nickel and manganese tended to increase. The levels of heavy metals in the effluent were lower than the limit values of the Dominican wastewater discharge standards. The construction cost of these facilities was around 200 USD per population equivalent, similar to the cost in other countries in the same region. This study suggested some solutions to the improved performance of CWs: selection of a microbial flora that guarantees the reduction of nitrates and nitrites to molecular nitrogen, use of endemic plants that bioaccumulate heavy metals, combination of constructed wetlands with filtration on activated carbon, and inclusion of water purification processes that allow to evaluate the reuse of treated water.

FeCa-based layered double hydroxide, a high-performance phosphorus adsorbent in constructed wetlands and ecological dams - A pilot scale study

Research studies have modified traditional substances to seek fast-acting removal of phosphorus in constructed wetlands (CWs) and ecological dams, rather than develop a brand-new nano-adsorbent. This work synthesized FeCa-based layered double hydroxide (FeCa-LDH) with a chemical co-precipitation method, and the performance, mechanism and factors of phosphorus removal were investigated. FeCa-LDH showed a marked ability to adsorb phosphorus from waste water, with a removal efficiency of 94.4% and 98.2% in CWs and ecological dams, respectively. Both FTIR and XPS spectrum evidenced that FeCa-LDH removed phosphorus via electrostatic and hydrogen-bonding adsorption, as well as a coordination reaction and interlayer anion exchange. FeCa-LDH showed a higher capacity to remove phosphorus in alkaline and neutral waste water than in acid conditions. Co-occurrence anions, which influenced the efficiency of the phosphorus removal capacity are considered in the sequence below: CO32− ≈ HCO3− > SO42− > NO3−. Innovatively, FeCa-LDH was not affected by the low-temperature limitation for CWs, and phosphorus removal efficiency at 5 °C was almost equal to that at 25 °C. These results cast a new idea on the construction, application and phosphorus removal performance of CWs and ecological dams.

Nanobubble aeration enhanced wastewater treatment and bioenergy generation in constructed wetlands coupled with microbial fuel cells

Artificial aeration is a widely used approach in wastewater treatment to enhance the removal of pollutants, however, traditional aeration techniques have been challenging due to the low oxygen transfer rate (OTR). Nanobubble aeration has emerged as a promising technology that utilise nano-scale bubbles to achieve higher OTRs owing to their large surface area and unique properties such as longevity and reactive oxygen species generation. This study, for the first time, investigated the feasibility of coupling nanobubble technology with constructed wetlands (CWs) for treating livestock wastewater. The results demonstrated that nanobubble-aerated CWs achieved significantly higher removal efficiencies of total organic carbon (TOC) and ammonia (NH4+-N), at 49 % and 65 %, respectively, compared to traditional aeration treatment (36 % and 48 %) and the control group (27 % and 22 %). The enhanced performance of the nanobubble-aerated CWs can be attributed to the nearly three times higher amount of nanobubbles (Ø < 1 μm) generated from the nanobubble pump (3.68 × 108 particles/mL) compared to the normal aeration pump. Moreover, the microbial fuel cells (MFCs) embedded in the nanobubble-aerated CWs harvested 5.5 times higher electricity energy (29 mW/m2) compared to the other groups. The results suggested that nanobubble technology has the potential to trigger the innovation of CWs by enhancing their capacity for water treatment and energy recovery. Further research needs are proposed to optimise the generation of nanobubbles, allowing them to be effectively coupled with different technologies for engineering implementation.

Stimulation on microbial nitrogen metabolism by iron under PFAS exposure drives effective nitrogen removal in constructed wetland

Constructed wetlands (CWs) have been employed for treatment of perfluoroalkyl substances containing wastewater. However, suppression on operation performances of CWs was inevitable, particularly on nitrogen removal. In this study, 10–30 mg/L nano zero-valent iron (nZVI) was introduced into CWs because of its potential for driving effective nitrogen removal via promoting functional microbes. Perfluorooctanoic acid (PFOA) exposure led to reduction of ammonia (NH4+-N) transformation, but stimulated nitrate (NO3−-N) removal by up to 83.12 %. With PFOA exposure, 10 mg/L nZVI caused the most significant improvement on NH4+-N removal, with maximum increase of 3.65 %. By contrast, 30 mg/L nZVI was prone to alleviate NO3−-N accumulation by 14.19–24.22 % compared to control group. Lower dosage of nZVI (10–20 mg/L) increased activity of five nitrogen cycling enzymes by 31.42–315.18 % in maximum. Whereas, 30 mg/L nZVI led to limited promotion or even inhibition on these enzymes. Analogously, stimulation on nitrifying, anammox, and denitrifying bacteria, as well as functional key genes were more obvious by nZVI at lower concentration. Besides, nZVI reduced functional gene of dissimilatory nitrate reduction to ammonium and related bacteria, increasing NH4+-N removal indirectly. The most promotion on nitrate dependent Fe oxidation bacteria like Paracoccus could explain improvement on NO3−-N removal by 30 mg/L nZVI.

Environmental performance of constructed wetland planted with monocultures and polycultures for wastewater treatment

The effects of culture systems and seasonality on the environmental impact of constructed wetlands (CWs) remain understudied. This study aims to quantify the environmental impact of common and ornamental plants in a pilot-scale horizontal subsurface flow (HSSF) CW planted with monocultures and a polyculture. Eight scenarios were evaluated, differentiated by plant type, culture system, and season (warm season, cold season). Environmental performance was evaluated using the life cycle assessment (LCA) methodology. The environmental impact index (ƐP), based on eutrophication reduction (kgP removed), and net environmental benefit (NEB) indicators were also calculated. The results showed that a CW planted with polycultures reduced FE by 5–17% compared to those planted in monocultures. However, the polyculture had the highest environmental impact in the GW category, up to 1.5–9 times higher than that of monocultures. Furthermore, there was better performance in the cold season in all scenarios. Specifically, NEB showed an environmental benefit for freshwater eutrophication and a negative benefit for global warming. The ƐP indicator was inversely proportional to the elimination of phosphorus, with the polyculture CW reaching the highest values of 3399 kgCO2eq/kgP removed in the warm season. The assessment of environmental impact patterns could support the development of strategies for better environmental performance of CWs, with polycultures used as an alternative wastewater treatment.

Exploring the resilience of constructed wetlands to harmful algal blooms disturbances: A study on microbial response mechanisms

Constructed wetlands (CWs) have emerged as a promising environmentally sustainable technique for wastewater treatment. However, the susceptibility of CWs to disturbances caused by harmful algal blooms (HABs) raises concerns. This study aimed to investigate the impact of HABs on the pollutants’ removal performance of CWs and the response of rhizosphere microbial community. Results revealed that CWs possessed an adaptive capacity that enabled them to recover caused by HABs. The rhizosphere was found to stimulate the occurrence of Acinetobacter, which played a critical role to help resist HABs disturbance. This study also observed an increased dissimilatory nitrate reduction metabolic pathway which promoted denitrification and enhanced the nitrogen removal efficiency of CWs. Additionally, the structural equation model further suggested that dissolved oxygen exerted a significant influence on the microbial activities and then affected the pollutants removal performance. Overall, our findings shed light on the mechanism for CW stability maintenance during HABs disturbance.

Impact of a natural disturbance on the performance and microbial communities in a full-scale constructed wetland for industrial wastewater treatment

Constructed Wetlands (CWs) are a cost-effective, versatile and sustainable choice for wastewater treatment. In these environments, microbial communities play a significant role in pollutant removal. However, little is known about how microbial communities in full-scale CWs contribute to maintaining water quality or how their dynamics change in response to pulse disturbances such as fire or freezes. Furthermore, few studies have examined the relationship between CW microbial community structure and performance in full-scale industrial operations. We characterized the water-column and leaf-litter layer microbial communities in a 110-acre free water surface CW that provides tertiary wastewater treatment to a plastics manufacturing plant. The CW’s sampling campaign was conducted over a 12-month period that included Winter Storm Uri, a 100-year freeze event. Analysis of 16S rRNA gene amplicon sequences revealed that the bacterial communities experienced a temporal shift. There was also a shift in microbial community structure between the influent and the first segment of the CW. However, no differences in microbial community structure were observed in the second segment of the CW. There was a negative association between microbial community diversity and chlorophyll a, as well as microbial community diversity and total suspended solids (TSS); demonstrating an increase in microbial biodiversity as water quality improved throughout the CW. Six months after the freeze, CW performance in terms of removal of water quality constituents began to return to former removal trends. Yet, there was still a significant difference in microbial community structure within the CW relative to the previous year. This suggests CW functional resilience despite a shift in microbial community structure in the wetland.