Performance Of Constructed Wetlands Research Articles

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.

The enhancement of nutrients removal performance in a vertical up-flow constructed wetland system using iron-carbon substrates

The reclaimed water was usually further treated by the constructed wetland (CW) to remove nitrogen and phosphorus before it was discharged to water bodies. In this work, the iron-carbon (Fe-C) substrate and plant-based carbon source were added to the vertical up-flow CWs to enhance the denitrification of reclaimed water. It was found that the removal efficiency of nitrate (NO3--N), total nitrogen (TN) and total phosphorus (TP) in the Fe-C amended CWs were significantly increased by 20–35%, 10–25%, and 10–35%. Moreover, the plant-based carbon source also contributed to TN and TP removal. The additional substrates also reduced the emission of NO2 and CH4 from the CWs. Finally, the microbial community was analyzed to disclose the mechanism involved in the enhanced performance of CWs. The enriched hydrogenotrophic and heterotrophic denitrifiers by the Fe-C substrates and pine bark contributed to the enhanced nitrification.

Efficient removal mechanism of an electrical conductivity-enhanced constructed wetlands under particle accumulated conditions

The performance of constructed wetland (CWs) systems should improve through the electrochemistry of microorganisms, with the help of conductive fillers. To explore the strengthening mechanism of the CWs, three comparative experiments, including Co CWs (electro-conductive materials coke as filler), Co-P CWs (coke as filler with pickerel weed (Pontederia cordata L)), and QS-P CWs (quartz sand as filler with pickerel weed (Pontederia cordata L)), were tested to investigate the influence of the clogging process on the purification capacity from the electrochemical characteristics and the community of microorganisms in domestic sewage. The results showed that coke, as an electro-conductive filler, had the best organic removal and high electric output, even with solid particle accumulation. Co-P CWs were the most stable and had the best removal efficiency of COD (chemical oxygen demand) in urban sewage, with an average removal rate of 74.9% at 7 weeks, which was 14 and 7.3% higher than those of the QS-P CWs and Co CWs, respectively. The power generation performance of the Co-P CWs was also the best. During operation, the voltage remained the highest (377.9–222.0 MV). The microbial community diversity, richness, and utilization rate of the six categories of carbon sources of Co-P CWs were the highest, with the dominant genera being organic matter aerobic degrading bacteria, electrochemically active bacteria, and ammonia-oxidizing bacteria. The microbial richness in coke CWs exhibited high microbial activity in the entire bed, not only at the inlet. This indicates that the system transfers electrons to the conductive material by relying on the metabolism of microorganisms; electrons generated at the bottom of the bed are directly transmitted to the bed surface through the conductive material, resulting in a uniform distribution of electrons throughout the bed and high microbial activity. Therefore, the conductivity-enhanced CWs effectively alleviated the reduction in wetland purification capacity.

Effects of macrophytes on micro – And nanoplastic retention and cycling in constructed wetlands

Macrophytes play the important roles in purifying pollutants of constructed wetlands (CWs), while their effects on CWs exposed to micro/nano plastics are not clear. Therefore, planted and unplanted CWs were established to reveal the impacts of macrophytes (Iris pseudacorus) on the overall performance of CWs under polystyrene micro/nano plastics (PS MPs/NPs) exposure. Results showed that macrophytes effectively enhanced the interception capacities of CWs to PS NPs, and significantly promoted the removal of nitrogen and phosphorus after exposed to PS MPs/NPs. Meanwhile, macrophytes improved the activities of dehydrogenase, urease, and phosphatase. Sequencing analysis showed that macrophytes optimized the composition of microbial communities in CWs and stimulated the growth of functional bacteria involved in nitrogen and phosphorus transformation. Moreover, macrophytes further altered the absolute abundance of nitrogen transformation functional genes (amoA, nxrA, narG and nirS). Functional annotation analysis revealed that macrophytes promoted metabolic functions such as Xenobiotics, Amino acids, Lipids metabolism and Signal transduction, ensuring the metabolic balance and homeostasis of microbes under PS MPs/NPs stress. These results exhibited profound implications for the comprehensive evaluation on the roles of macrophytes in CWs for treating wastewater containing PS MPs/NPs.

Do mycorrhizal symbiosis affect wastewater purification in constructed wetlands with different substrates?

Arbuscular mycorrhizal fungi (AMF) can play important roles in pollutant removal in the terrestrial system. However, the functional role of AMF in wetland systems is still unclear. This study evaluated the effects of AMF on the purification of the pharmaceuticals and personal care products (PPCPs) containing wastewater in constructed wetlands (CWs) filled with different substrate types (sand, perlite, vermiculite or biochar). Results indicated that the removal efficiencies of total organic carbon (TOC), phosphate (PO43−-P), and total nitrogen (TN) in CWs with different substrates were in the following order: biochar > vermiculite > perlite > sand. Compared with sand systems, the removal efficiencies of TOC, PO43−-P, ammonium (NH4+-N), and TN in CWs filled with adsorptive substrates (biochar, vermiculite, or perlite) were enhanced by 3.8–11.4 %, 11.6–30.6 %, 16.5–31.2 %, and 6.2–34.6 %, respectively. AM symbiosis increased TOC, TN, and PO43−-P removal in CWs but the adsorptive substrates showed more significant influences on wastewater purification than AMF symbiosis. Besides, plant (Glyceria maxima) presence also improved the performance of CWs on wastewater purification. Overall, all the findings indicated that the interaction effects of AM symbiosis and adsorptive substrates (e.g., biochar, vermiculite, or perlite) could enhance the removal performance of pollutants from wastewater in planted CWs.

Silver nanoparticles disturb treatment performance in constructed wetlands: Responses of biofilm and hydrophyte

As widely used in many kinds of products, silver nanoparticles (AgNPs) are inevitably released into the aquatic environment. Constructed wetlands (CWs) are essential sinks of AgNPs, while little is known about the responses of microorganisms (biofilm on the substrate surface) and hydrophyte functions to AgNPs accumulation in CWs. Given that, we conducted a 60-day experiment exposing to 1 and 50 mg L−1 of AgNPs in CWs. Results revealed that AgNPs accumulation obviously decreased the relative abundance of genes involved in biofilm formation and microbial nitrogen metabolism, whereas increased those in the glycolysis process; AgNPs also decreased key enzyme activities corresponding to nutrient removal. In addition, AgNPs accumulation decreased the hydrophyte activity, causing a decline in the uptake ability of C (6%–44%), N (17%–54%), and P (14%–56%) elements. Finally, due to the decline in the whole biofilm and hydrophyte functions under AgNPs exposure, the treatment performance of CWs significantly decreased by 40%–56% of total nitrogen and 44%–60% of ammonia nitrogen, respectively. Overall, our results first revealed biofilm and hydrophyte's functional response to AgNPs exposure. We systematically analyzed the changes of vital functional modules of microorganisms based on the metagenomic analysis, as well as the functional emergency response of aboveground and underground tissues of hydrophyte in CWs under AgNPs stress.

Integrated treatment of suburb diffuse pollution using large-scale multistage constructed wetlands based on novel solid carbon: Nutrients removal and microbial interactions

In this study, an integrated treatment system was proposed and applied in situ, including detention tank, multistage constructed wetlands (CWs) and wastewater treatment plants (WWTPs), preventing nutrients flowing into Dianchi Lake, in which the treatment performance of multistage CWs were evaluated principally. Results skillfully realized the bypass purification of upstream river at dry reasons, as well as the effective management and treatment of the collected diffuse pollution at rainy reasons. The purified water flowing into water bodies could satisfy the Grade III of environmental quality standards for surface water in China with the average effluent concentrations of COD, NH4+-N, TN and TP decreased to 10 (51.2–72.7%), 0.5 (67.2–83.0%), 1.0 (71.2–79.6%) and 0.15 (72.3–89.4%) mg L−1, respectively. High-throughput sequencing results indicated that the application of poly-3-hydroxybutyrate-cohyroxyvelate-sawdust (PS) blends could enrich norank_f_Anaerolineaceae (7.95%) and Bradyrhizobium (10.2%), which were distinct from the dominant genera of Pleurocapsa (13.0%) in gravel-based CWs. Functional genes and metabolism analysis uncovered that the heterotrophic denitrification was the main pathway of nitrogen removal with the abundance of genes encoding TCA cycle, glycolysis and denitrification process up-regulated. In addition, molecular ecological network (MEN) analysis suggested the denitrification genes were positively correlated with the predominant microbes in PS-based CWs, favorable for denitrifiers to transfer and utilize electron donors during denitrification process. This study proved that the developed PS blends as carbon supplies in CWs and the proposed integrated treatment system are effective methods for watershed management, providing valuable reference to low-pollution wastewater treatment in practical engineering projects.

Optimization of constructed wetlands on purifying black-odorous water and their potential purification mechanism.

Black-odorous water has become a common and widespread problem in recent decades. In this study, nine constructed wetlands (CWs) with different flow types, filters, plants, and hydraulic loadings were designed according to an orthogonal array (L9 (34), and were used for the purification of black-odorous water in summer and winter. The results showed that CWs are regarded as effective to purify black-odorous water in both seasons. Microbial degradation is the major removal pathway of pollutants in CWs during summer, while the joint effect of biodegradation and adsorption is the main treatment route during winter. Flow type and hydraulic loading appear to be the most important factors impacting the purification performance of CWs, by changing the redox condition of systems and retention time of contaminants, respectively. 'Vertical flow-zeolite filter-high loading' is proposed as the best parameter selection for CWs on the purification of black-odorous water: among them, CWs with vertical flow have better oxygen transport capacity that is conductive to aerobic processes of pollutants, zeolite substrates may adsorb more nitrogen via ion exchange, higher hydraulic loadings can extend the contact time between contaminants and filters, and regulate the water temperature for microbial activity.

Removal of Heavy Metals from Acid Mine Drainage with Lab-Scale Constructed Wetlands Filled with Oyster Shells

The present study investigated the applicability of constructed wetlands (CWs) filled with oyster shells (OSs) for removing heavy metals from acid mine drainage (AMD). Lab-scale CWs consisted of columns (ID 12.5 cm, H 50 cm) packed with OSs or limestone, which were left unplanted or planted with cattails. Synthetic and real AMD containing 7.3 mg/L of Zn, 38.0 mg/L of Fe, and other minerals (pH = 4.0) were fed to the CWs (1 L/column) under a hydraulic retention time of 7 days in a sequencing batch mode. The effluent pH values of the CWs reached 6.9–8.3. Results show that OSs with high CaCO3 contents had higher neutralizing capability for AMD than limestone had. During 7 months of operation, all CWs were highly effective for removing Zn (88.6–99.2%); Fe (98.7–99.7%); and Cd, Cu, Pb, As, and Mn (48.2–98.9%) from both real and synthetic AMD. The mass balance in the CWs indicated accumulation in OSs or limestone as a main pathway for removing heavy metals, representing 44.8–99.3% of all metals, followed by biomass (8.8–29.9%) in the planted CWs. Other processes examined for this study only played a minor role in removing heavy metals. The higher metal treatment performance of OS CWs demonstrated the value of this aquaculture byproduct as a CW substrate.

Performance evaluation of constructed wetland for removal of pharmaceutical compounds from hospital wastewater: Seasonal perspective

Constructed wetland employs vegetation as a natural medium to remove pollutants from wastewater for this treatment. It is eco-friendly, sustainable, economical, low maintenance, low running cost, and easy to use. This has prompted several studies to investigate its performance in treating pollutants from the conventional to emerging contaminants category, including pharmaceutical compounds. However, there is still a lack of work on the impact of monsoons on the removal efficiency of pharmaceutically active compounds from wastewater. This study evaluated constructed wetland performance during the premonsoon, monsoon, and post-monsoon seasons. A pilot-scale constructed wetland setup was established to conduct this study. The target compound included paracetamol, ibuprofen, carbamazepine, lorazepam, ciprofloxacin, sulfamethoxazole, and Fluvastatin. In the constructed wetland, for paracetamol and ibuprofen, NSAIDs concentration was observed to be 1503–6307 ngL−1 and 564–808 ngL−1. The concentrations of antibiotics, sulfamethoxazole, and ciprofloxacin were 16532–21635 ngL−1 and 734–1178 ngL−1, respectively. The carbamazepine, lorazepam, and Lutvastatin concentration range was 616–906 ngL−1, 2742–3775 ngL−1, and 694–2068 ngL−1, respectively. The hazard quotient approach was adopted to evaluate potential environmental risk from target compounds. The increase of paracetamol 33 %, ibuprofen 94 %, ciprofloxacin 242 %, Sulfamethoxazole 64 %, and carbamazepine 77 % validated the study hypothesis. However, a decrease of 15 % lorazepam and 43 % Fluvastatin inferred that dilution was inversely proportional to the removal of these compounds. The seasonal removal efficiency was in order pre-monsoon < post-monsoon < monsoon. Hospital wastewater had HQ values of 90, 100, and 130 for premonsoon, monsoon, and post-monsoon, respectively. After treatment from the constructed wetland, the wastewater effluent had reduced HQ value to 53, 35, and 70 for premonsoon, monsoon, and post-monsoon periods respectively. The HQ values were further reduced in tubesettler to 22, 11, and 28. Ciprofloxacin posed no significant risk. However, sulfamethoxazole posed a high risk during premonsoon, monsoon, and post-monsoon season. Further works are required to analyze the removal mechanism through plant uptake, sediment bed, and biodegradation for a different season or climatic condition to present the real-time performance of constructed wetlands for treating wastewater loaded with pharmaceutical compounds.

Comparison of constructed wetland performance coupled with aeration and tubesettler for pharmaceutical compound removal from hospital wastewater

Pharmaceutical compounds being able to alter, retard, and enhance metabolism has gained attention in recent time as emerging pollutant. However, hospitals which are part of every urban landscape have yet to gain attention in terms of its hospital wastewater treatment to inhibit pharmaceutical compounds from reaching environment. Hence this study evaluated performance of constructed wetland in combination with tubesettler and aeration based on removal efficiency and ecological risk assessment (HQ). The removal efficiency of constructed wetland with plantation was higher by 31% (paracetamol), 102% (ibuprofen), 46%, (carbamazepine), 57% (lorazepam), 54% (erythromycin), 31% (ciprofloxacin) and 20% (simvastatin) against constructed wetland without plantation. Constructed wetland with aeration efficiency increased for paracetamol, ibuprofen, carbamazepine, lorazepam, erythromycin, ciprofloxacin, and simvastatin removal efficiency were higher by 58%, 130%, 52%, 79%, 107%, 57%, and 29% respectively. In constructed wetland with plantation, removal efficiency was higher by 20% (paracetamol), 13% (ibuprofen), 4% (carbamazepine), 14% (lorazepam), 34% (erythromycin), 19% (ciprofloxacin) and 7% (simvastatin). High ecological risk was observed for algae, invertebrate and fish with hazard quotient values in range of 2.5–484, 10–631 and 1–78 respectively. This study concludes that if space is the limitation at hospitals aeration with constructed wetland can be adopted. If space is available, constructed wetland with tubesettler is suitable, economic and environmentally friendly option. Future research works can focus on evaluating other processes combination with constructed wetland.

An innovative reuse of bottom ash from municipal solid waste incinerators as substrates of constructed wetlands

The incineration of municipal solid waste has been important in waste management, but it raises another environmental issue concerning residue treatment. This study describes an innovative use of naturally aged incineration bottom ash (AIBA) as an alternative substrate for horizontal subsurface flow (HSSF) constructed wetlands (CW). Although experimental results from a period lasting for 396 days only revealed slightly higher removal ratios in HSSF with AIBA (HSSF-E) than in HSSF-traditional pebble beds (HSSF-C), increasing from 67% to 76% for BOD, 44%–51% for TKN, 47%–54% for NH3-N, and 44%–52% for TN. The data indicate that the use of AIBA in HSSF CW can achieves a certain removal efficiency of BOD and nitrogen species. Interestingly, the total phosphorus removal rates also increased significantly from 20% in HSSF-C to 36% in HSSF-E. These observations on the use of AIBA in HSSF CW confirmed that AIBA is a suitable alternative for use as a substrate for HSSF CWs and identified an additional way to reuse incineration bottom ash. Design criteria for a CW using AIBA as a partial substrate is proposed to improve the pollutant removal performance of HSSF CWs.

Ecological restoration performance enhanced by nano zero valent iron treatment in constructed wetlands under perfluorooctanoic acid stress

Perfluorooctanoic acid (PFOA) of widespread use can enter constructed wetlands (CWs) via migration, and inevitably causes negative impacts on removal efficiencies of conventional pollutants due to its ecotoxicity. However, little attention has been paid to strengthen performance of CWs under PFOA stress. In this study, influences of nano zero valent iron (nZVI), which has been demonstrated to improve nutrients removal, were explored after exemplifying threats of PFOA to operation performance in CWs. The results revealed that 1 mg/L PFOA suppressed the nitrification capacity and phosphorus removal, and nZVI distinctly improved the removal efficiency of ammonia and total phosphorus in CWs compared to PFOA exposure group without nZVI, with the maximum increases of 3.65 % and 16.76 %. Furthermore, nZVI significantly stimulated dehydrogenase (390.64 % and 884.54 %) and urease (118.15 % and 246.92 %) activities during 0–30 d and 30–60 d in comparison to PFOA group. On the other hand, nitrifying enzymes were also promoted, in which ammonia monooxygenase increased by 30.90 % during 0–30 d, and nitrite oxidoreductase was raised by 117.91 % and 232.10 % in two stages. Besides, the content of extracellular polymeric substances (EPS) under nZVI treatment was 72.98 % higher than PFOA group. Analyses of Illumina Miseq sequencing further certified that nZVI effectively improved the community richness and caused the enrichment of microorganisms related to nitrogen and phosphorus removal and EPS secreting. These results could provide valuable information for ecological restoration and decontamination performance enhancement of CWs exposed to PFOA.

Iris pseudacorus as precursor affecting ecological transformation of graphene oxide and performance of constructed wetland

The role of plants is largely unknown in constructed wetlands (CWs) exposed to phytotoxic nanomaterials. Present study investigated transformation of graphene oxide (GO) and performance of CWs with Iris pseudacorus as precursor. GO was trapped by CWs without dependence on plants. GO could move to lower substrate layer and present increases on defects/disorders with stronger effects in planted CW. Before adding GO, planted CW achieved better removal both of phosphorus and nitrogen. After adding GO, phosphorus removal in planted CW was 93.23–95.71% higher than 82.55–90.07% in unplanted CW. However, total nitrogen removal was not improved, showing 48.20–56.66% and 53.44–56.04% in planted and unplanted CWs. Plant improved urease, phosphatase, and arylsulfatase, but it decreased β-glucosidase and had less effects on dehydrogenase and catalase. Pearson correlation matrix revealed that plant enhanced microbial interaction with high degree of positive correlation. Moreover, there were obvious shifts in microbial community at phylum and genus level, which presented closely positive action on substrate enzyme activities. The functional profile was less affected due to functional redundancy in microbial system, but time effects were obvious in CWs, especially in planted CW. These findings could provide the basis on understanding role of plants in CWs for treating nanoparticles wastewater.

A review on constructed wetlands-based removal of pharmaceutical contaminants derived from non-point source pollution

In the current decade, Non-Point Source (NPS) pollution has become a critical global problem in both developing and developed countries. As a result of diverse human activities, NPS pollution has led to an excessive supply of inorganic nutrients (e.g., phosphorus, nitrogen, and metals) and organic compounds (e.g., pharmaceutical compounds and pesticides) into soils and surface waters which change the water quality. Continuous discharge of pollutants by NPS source mainly affects the soil and aquatic ecosystem, damaging the food chain and food web that exist in this Earth planet. On such a serious note, methods to mitigate the pollutants derived from NPS sources or treatment methods could effectively reduce the contaminant load. Recently, the use of constructed wetlands (CWs) for bioremediation purposes has been gaining considerable attention in many countries since they mostly mimic the natural and eco-friendly process for mitigating various types of pollutants. Although their successful use in the treatment of point source pollutants is well documented, information on the performance of CWs for treating organic pollutants, particularly pharmaceutical residues, is still not adequately summarized. Therefore, this paper focuses on outlining and reviewing the current information related to the use of CWs in mitigating pharmaceutical contaminants (PCs) in soil and water reservoirs. Firstly, we summarized the key aspects on sources, occurrence, fate, and ecotoxicological effects of most common pharmaceuticals derived by NPS pollution. The second objective deals with the significance of plants present in CWs that help PCs remove via various possible mechanisms. Thirdly, we discuss the roles and importance of other factors (e.g., microorganism, temperature, and substrate) to remove PCs efficiently. Overall, this review highlights the current state-of-art of CWs for mitigating NPS-derived PCs and presses the area where future research is required to make the CWs application more successful shortly.

Removing nutrients from wastewater by constructed wetlands under perfluoroalkyl acids stress

Constructed wetlands (CWs) are often used to treat wastewater discharged from wastewater treatment plants (WWTPs), while emerging contaminants (such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS)) have been commonly discovered in WWTPs. However, no research has examined whether PFOA/OS (i.e. PFOA and PFOS) affects the performance of CW. Therefore, this study compared the nutrient removal efficiencies of four CWs with varied configurations under PFOA/OS and no PFOA/OS stress conditions. We found that CW containing plants or/and iron-carbon had higher removal efficiency for nutrients (except NH4+–N) than conventional CW in stable operation under wastewater without PFOA/OS. Plants or/and iron increased the nutrient removal efficiency by plant uptake, chemical reaction, and co-precipitation of iron hydroxides. In contrast, the iron-carbon inhibited the nitrification of nitrifying bacteria by consuming dissolved oxygen, converting NO3−–N to NH4+–N. Although the removal efficiencies of nutrients by CWs differed after introducing PFOA/OS, the removal order was consistent with those before adding PFOA/OS. Plants or/and iron-carbon effectively increased CWs’ resistance to PFOA/OS loading and toxicity, and the function of iron-carbon was superior to the plants. In addition, PFOA/OS reduced the abundances of microbes Hydrogenophaga, Pseudomonas, Sphingomonas, Nitrospira, and Candidatus_Accumulibacter that contributed to nutrient removal.

Improper Maintenance Activities Alter Benefits of Urban Stormwater Treatment in a Temperate Constructed Wetland in NSW, Australia

Constructed wetlands (CWs) are an effective means to treat nutrient and sediment pollution in urban stormwater runoff to minimise impact on receiving waterways. Maintenance of devices is recognised as a major contributing factor to performance. There is a lack of evidence-based guidance on maintenance activities to optimise treatment, due to a paucity of data from long-term field studies into CW performance before and after maintenance. In this study, the nutrient and sediment removal efficiency (% RE) of a CW was evaluated by calculating removal efficiencies of nitrogen (N), phosphorus (P) and total suspended sediment (TSS) following a long-term sampling program under baseflow and event flow conditions. Sampling was carried out before, during and after maintenance. Maintenance involved removing all aquatic vegetation and 200–300 mm of sediments over a 3-week period, aiming to improve the wetland’s performance. Assessment of dissolved and particulate nutrient fractions allowed a comprehensive investigation into drivers of nutrient removal efficiency. Under baseflow conditions differences in inflow and outflow pollutant concentrations were used to calculate removal efficiency and pollutant loads were used during event flow conditions. Before maintenance, during baseflow conditions the wetland was removing total N (36% RE) but exporting total P (-52% RE) and total sediment (-94% RE). During event-flow conditions all target pollutants were being removed (total N 63% RE, total P 25% RE and TSS 69% RE). phosphorusDuring maintenance, the device continued to remove total N (18% RE) but the physical disturbance of the maintenance resulted in mass export of total P (-120% RE) and total sediment (−2,000% RE) over a short time period, effectively undoing previous treatment. After maintenance, during baseflow conditions, the wetlands’ ability to treat total N decreased (28% RE), improved for total P (1% RE), and became a chronic source of suspended sediment (−127% RE). During event flow conditions, total N was no longer being treated (−19%) but total P and total suspended sediment were being retained (74%, 80% RE respectively). This study showed that the physical disturbance resulting from large-scale maintenance activities can potentially reverse years’ worth of treatment if not adequately planned and carried out with suitable controls.

Wetland Construction, Restoration, and Integration: A Comparative Review

In response to the global loss and degradation of wetland ecosystems, extensive efforts have been made to reestablish wetland habitat and function in landscapes where they once existed. The reintroduction of wetland ecosystem services has largely occurred in two categories: constructed wetlands (CW) for wastewater treatment, and restored wetlands (RW) for the renewal or creation of multiple ecosystem services. This is the first review to compare the objectives, design, performance, and management of CW and RW, and to assess the status of efforts to combine CW and RW as Integrated Constructed Wetlands (ICW). These wetland systems are assessed for their ecological attributes and their relative contribution to ecosystem services. CW are designed to process a wide variety of wastewaters using surface, subsurface, or hybrid treatment systems. Designed and maintained within narrow hydrologic parameters, CW can be highly effective at contaminant transformation, remediation, and sequestration. The ecosystem services provided by CW are limited by their status as high-stress, successionally arrested systems with low landscape connectivity and an effective lifespan. RW are typically situated and designed for a greater degree of connection with regional ecosystems. After construction, revegetation, and early successional management, RW are intended as self-maintaining ecosystems. This affords RW a broader range of ecosystem services than CW, though RW system performance can be highly variable and subject to invasive species and landscape-level stressors. Where the spatial and biogeochemical contexts are favorable, ICW present the opportunity to couple CW and RW functions, thereby enhancing the replacement of wetland services on the landscape.

Particularities of Fungicides and Factors Affecting Their Fate and Removal Efficacy: A Review

Systemic fungicide use has increased over the last decades, despite the susceptibility of resistance development and the side effects to human health and the environment. Although herbicides and insecticides are detected more frequently in environmental samples, there are many fungicides that have the ability to enter water bodies due to their physicochemical properties and their increasing use. Key factors affecting fungicide fate in the environment have been discussed, including the non-target effects of fungicides. For instance, fungicides are associated with the steep decline in bumblebee populations. Secondary actions of certain fungicides on plants have also been reported recently. In addition, the use of alternative eco-friendly disease management approaches has been described. Constructed Wetlands (CWs) comprise an environmentally friendly, low cost, and efficient fungicide remediation technique. Fungicide removal within CWs is dependent on plant uptake and metabolism, absorption in porous media and soil, hydrolysis, photodegradation, and biodegradation. Factors related to the efficacy of CWs on the removal of fungicides, such as the type of CW, plant species, and the physicochemical parameters of fungicides, are also discussed in this paper. There are low-environmental-risk fungicides, phytohormones and other compounds, which could improve the removal performance of CW vegetation. In addition, specific parameters such as the multiple modes of action of fungicides, side effects on substrate microbial communities and endophytes, and plant physiological response were also studied. Prospects and challenges for future research are suggested under the prism of reducing the risk related to fungicides and enhancing CW performance.