The Use of Constructed Wetland for Mitigating Nitrogen and Phosphorus from Agricultural Runoff: A Review

Five coexisting brominated flame retardants in a water-sediment-Vallisneria system: Bioaccumulation and effects on oxidative stress and photosynthesis

The pollution of various brominated flame retardants (BFRs) is concurrence, while their environmental fate and toxicology in water-sediment-submerged plant systems remain unclear. In this study, Vallisneria natans plants were co-exposed to 2,3,4,5,6-pentabromotoluene (PBT), hexabromobenzene (HBB), 1,2-bis (2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenyl ether (BDE209), and decabromodiphenyl ethane (DBDPE). The ∑BFRs concentration in the root was 2.15 times higher than that in the shoot. Vallisneria natans accumulated more BTBPE and HBB in 0.2, 1, and 5 mg/kg treatments, while they accumulated more DBDPE and BDE209 in 25 and 50 mg/kg treatments. The bioaccumulation factors in the shoot and root were 1.08-96.95 and 0.04-0.70, respectively. BFRs in sediments had a more pronounced effect on bioaccumulation levels than BFRs in water, and biotranslocation was another potential influence factor. The SOD activity, POD activity, and MDA content were significantly increased under co-exposure. The DBDPE separate exposure impacted the metabolism of substances and energy, inhibited mismatch repair, and disrupted ribosomal functions in Vallisneria natans. However, DBDPE enhanced their photosynthesis by upregulating the expression level of genes related to the light reaction. This study provides a broader understanding of the bioaccumulation and toxicity of BFRs in submerged plants, shedding light on the scientific management of products containing BFRs.

Distinct roles of biochar and pyrite substrates in enhancing nutrient and heavy metals removal in intermittent-aerated constructed wetlands: Performances and mechanism

Constructed wetlands have been widely employed as a cost-effective and environmentally friendly alternative for treating primary and secondary sewage effluents. In this study, biochar and pyrite were utilized as electron donor substrates in intermittent-aerated vertical flow constructed wetlands to strengthen the nutrient and heavy metals removal simultaneously, and the response of nutrient reduction and microbial community to heavy metals stress was also explored. The results indicated that biochar addition exhibited a better nitrogen removal, while pyrite addition greatly promoted the phosphorus removal. Moreover, the high removal efficiencies of Cu2+, Pb2+ and Cd2+ (above 90%) except for Zn2+ were obtained in each system. However, the exposure of heavy metals decreased phosphorus removal while had little effect on nitrogen removal. The influent load and intermittent aeration implementation led to a significant shift in microbial community structures, but microbial biodiversity and abundance decreased under the exposure of heavy metals. Particularly, Thiobacillus and Ferritrophicum, associated with sulfur autotrophic denitrification and iron autotrophic denitrification, were more abundant in pyrite-based wetland systems.

Purification Effect of Water Eutrophication Using the Mosaic System of Submerged-Emerged Plants and Growth Response

Aquatic plants play a crucial role in the sustainable management of eutrophic water bodies, serving as a valuable tool for water purification. However, the effectiveness of using aquatic plants for improving water quality is influenced by landscape considerations. In practical applications, challenges arise concerning low purification efficiency and compromised aesthetic appeal when utilizing plants for water purification. To address these issues, this study aimed to examine the impact of aquatic plants on the purification of simulated landscape water bodies, specifically focusing on the effectiveness of the mosaic system of submerged-emerged plants in remediating eutrophic water bodies. Our findings indicated that individual aquatic plants exhibited limited efficacy in pollutant (total nitrogen, total phosphorus, ammonia nitrogen, and chemical oxygen demand) removal. However, when combined in appropriate proportions, submerged plants could enhance species growth and improve the purification efficiency of polluted water bodies. Notably, the mosaic system of submerged-emerged plants neither significantly promoted nor inhibited the growth of each other, but it effectively removed pollutants from the simulated water bodies and inhibited turbidity increase. The comprehensive evaluation ranked the purification capacity as Canna indica-submerged plants combination (C + S) > Thalia dealbata-submerged plants combination (T + S) > Iris pseudacorus-submerged plants combination (I + S) > Lythrum salicaria-submerged plants combination (L + S). Both C + S and T + S configurations effectively mitigated the rise of water turbidity and offered appealing landscape benefits, making them viable options for practical applications in urban landscape water bodies. Our study highlights that a submerged-emerged mosaic combination is a means of water purification that combines landscape aesthetics and purification efficiency.

Impacts of landscape pattern on plants diversity and richness of 20 restored wetlands in Chaohu Lakeside of China

The recovery of wetland function and biodiversity conservation aroused considerable interest in the past decades. Although many advances have been achieved in revealing disturbing factors on plants diversity, the knowledge of biodiversity manipulation, landscape configuration and ecosystem process in restored wetlands remains incomplete. To address this issue, the landscape of 20 restored wetlands' vegetation was classified into five vegetation formations including: upland plants, wet grassland, emergent plants, floating plants and submerged plants. Meanwhile, the configuration of landscape, plants' function traits and the structure of plants communities of each wetland were analyzed. A total of 142 herbaceous plants were identified from 399 samples of 20 lakeside wetlands. The top five predominant species were Typha orientalis, Alternanthera philoxeroides, Phragmites australis, Echinochloa caudata, and Erigeron canadensis. The highest of diversity index was observed in upland plants with Shannon-Wiener index (H) of 0.92 while higher richness of plants was obtained in wet grassland with species of 88. In dry year, the immigration of upland xerophyte and obligated aquatic species to facultative area increased the biodiversity of the ecotone. Meanwhile, this change may also aggravate the diffusion risk of exotic invasive species Erigeron canadensis. Additionally, the results indicated that number and evenness of landscape outweighed Shannon diversity index (SHDI) of wetlands in shaping the richness and diversity of wetland plants. Whereas, the high value of maximum proportion of landscape (Pmax) have reduced the landscape evenness and species richness. A suggested Pmax of <0.5 was benefit for the stability and biodiversity of restored wetlands.

Industrial wastewater treatment using floating wetlands: a review

Industrial wastewater generated from various production processes is often associated with elevated pollutant concentrations and environmental hazards, necessitating efficient treatment. Floating wetlands (FWs) have emerged as a promising and eco-friendly solution for industrial wastewater treatment, with numerous successful field applications. This article comprehensively reviews the removal mechanisms and treatment performance in the use of FWs for the treatment of diverse industrial wastewaters. Our findings highlight that the performance of FWs relies on proper plant selection, design, aeration, season and temperature, plants harvesting and disposal, and maintenance. Well-designed FWs demonstrate remarkable effectiveness in removing organic matter (COD and BOD), suspended solids, nutrients, and heavy metals from industrial wastewater. This effectiveness is attributed to the intricate physical and metabolic interactions between plants and microbial communities within FWs. A significant portion of the reported applications of FWs revolve around the treatment of textile and oily wastewater. In particular, the application reports of FWs are mainly concentrated in temperate developing countries, where FWs can serve as a feasible and cost-effective industrial wastewater treatment technology, replacing high-cost traditional technologies. Furthermore, our analysis reveals that the treatment efficiency of FWs can be significantly enhanced through strategies like bacterial inoculation, aeration, and co-plantation of specific plant species. These techniques offer promising directions for further research. To advance the field, we recommend future research efforts focus on developing novel floating materials, optimizing the selection and combination of plants and microorganisms, exploring flexible disposal methods for harvested biomass, and designing multi-functional FW systems.

Soil pH influences the toxicity of Basamid® eluates to non-target species of primary consumers

Basamid® is a fumigant nematicide and fungicide known to break down in several volatile compounds, mainly methyl isothiocyanate (MITC), when in contact with water. Soil abiotic parameters, such as pH, influences this breakdown process, and thus, the toxic effects of Basamid® to aquatic biota. This work studied the influence of soil pH (5.5, 6.5 and 7.5) on the toxicity of eluates (1:4, m:v), obtained from Basamid®-contaminated soils (with the recommended dose of 145 mg of dazomet/Kg of soil), on two primary consumers: Daphnia magna and Brachionus calyciflorus. For this, lethal and sublethal toxicity of eluates originated from soils at pH 5.5, 6.5 and 7.5, contaminated with Basamid® (Ba-E 5.5; 6.5 and 7.5, respectively), were assessed (dilutions between 0.096 - 100%). The LD50,24h of Basamid® eluates for D. magna varied from 3.07% to 7.82% (Ba-E 6.5 and Ba-E 5.5 respectively), while for B. calyciflorus varied from 18.1% to 84.7% (Ba-E 6.5 and Ba-E 7.5, respectively). Both species were less sensitive to Basamid® eluates originated from soils with pH 7.5 and more sensitive to those obtained from soils with pH 6.5. Regarding the sublethal effects, a lower soil pH was associated with a higher toxicity of Basamid® to D. magna reproduction (LOED: 0.125% Ba-E 5.5), while for B. calyciflorus such a higher toxicity was observed at the highest soil pH (ED20: 7.42% [5.10-9.74] at Ba-E 7.5). These results show a negative association between soil pH and the lethal toxicity of Basamid® contaminated eluates. However, such a pattern was not observed at sublethal level, at which a species dependency was observed regarding the influence of soil pH in the observed toxicity. Nevertheless, it is to highlight that very low concentrations of eluates (as 3.07%) caused significant mortality, indicating a high risk for freshwater biota. Considering that Basamid® is likely to reach the aquatic systems is real, for which reason the recommended dose must be reviewed at environmentally-relevant scenarios.

Heavy Metal Pollution in the Environment and Its Impact on Health: Exploring Green Technology for Remediation

Along with expanding urbanization and industrialization, environmental pollution which negatively affects the surroundings, has been rising quickly. As a result, induces heavy metal contamination which poses a serious threat to living organisms of aquatic and soil ecosystems. Therefore, they are a need to ameliorate the effects cost by cost pollution on the environment. In this review, we explore methods employed to mitigate the effects caused by heavy metals on the environment. Many techniques employed to manage environmental pollution are tedious and very costly, necessitating the use of alternative management strategies to resolve this challenge. In this concept, bioremediation is viewed as a future technique, due to its environmental friendliness and cost-effective measures aligned with sustainable or climate-smart agriculture to manage contaminants in the environment. The technique involves the use of living entities such as bacteria, fungi, and plants to deteriorate toxic substances from the rhizosphere. Currently, bioremediation is thought to be the most practical, dependable, environmentally benign, and long-lasting solution. Although bioremediation involves different techniques, they are still a need to find the most efficient method for removing toxic substances from the environment. This review focuses on the origins of heavy metal pollution, delves into cost-effective and green technological approaches for eliminating heavy metal pollutants from the environment, and discusses the impact of these pollutants on human health.

Microbial community structure analyses and cultivable denitrifier isolation of Myriophyllum aquaticum constructed wetland under low C/N ratio

With the rapid expansion of livestock production, the amount of livestock wastewater accumulated rapidly. Lack of biodegradable organic matter makes denitrification of livestock wastewater after anaerobic digestion more difficult. In this study, Myriophyllum aquaticum constructed wetlands (CWs) with efficient nitrogen removal performance were established under different carbon/nitrogen (C/N) ratios. Analysis of community composition reveals the change of M. aquaticum CWs in microbial community structure with C/N ratios. The proportion of Proteobacteria which is one of the dominant phyla among denitrifier communities increased significantly under low C/N ratio conditions. Besides, to obtain cultivable denitrifier that could be added into CWs in situ, 33 strains belonging to phylum Proteobacteria were isolated from efficient M. aquaticum CWs, while the best-performing denitrification strain M3-1 was identified as Bacillus velezensis JT3-1 (GenBank No. CP032506.1). Redundancy analysis and quadratic models showed that C/N ratio had significant effects on disposal of nitrate (NO₃^--N) and the strains isolated could perform well in denitrification when C/N ratio is relatively low. In addition, they have relatively wide ranges of carbon sources, temperature and a high NO₃^- removal rate of 9.12 mg/(L·hr) at elevated concentrations of 800 mg/L nitrate. Thus, strains isolated from M. aquaticum CWs with low C/N ratio have a practical application value in the treatment of nitrate-containing wastewater. These denitrifying bacteria could be added to CWs to enhance nitrogen removal efficiency of CWs for livestock wastewater with low C/N ratio in the future.

Factors Influencing Gaseous Emissions in Constructed Wetlands: A Meta-Analysis and Systematic Review

Constructed wetlands (CWs) are an eco-technology for wastewater treatment and are applied worldwide. Due to the regular influx of pollutants, CWs can release considerable quantities of greenhouse gases (GHGs), ammonia (NH₃), and other atmospheric pollutants, such as volatile organic compounds (VOCs) and hydrogen sulfide (H₂S), etc., which will aggravate global warming, degrade air quality and even threaten human health. However, there is a lack of systematic understanding of factors affecting the emission of these gases in CWs. In this study, we applied meta-analysis to quantitatively review the main influencing factors of GHG emission from CWs; meanwhile, the emissions of NH₃, VOCs, and H₂S were qualitatively assessed. Meta-analysis indicates that horizontal subsurface flow (HSSF) CWs emit less CH₄ and N₂O than free water surface flow (FWS) CWs. The addition of biochar can mitigate N₂O emission compared to gravel-based CWs but has the risk of increasing CH₄ emission. Polyculture CWs stimulate CH₄ emission but pose no influence on N₂O emission compared to monoculture CWs. The influent wastewater characteristics (e.g., C/N ratio, salinity) and environmental conditions (e.g., temperature) can also impact GHG emission. The NH₃ volatilization from CWs is positively related to the influent nitrogen concentration and pH value. High plant species richness tends to reduce NH₃ volatilization and plant composition showed greater effects than species richness. Though VOCs and H₂S emissions from CWs do not always occur, it should be a concern when using CWs to treat wastewater containing hydrocarbon and acid. This study provides solid references for simultaneously achieving pollutant removal and reducing gaseous emission from CWs, which avoids the transformation of water pollution into air contamination.

A quantitative approach on environment-food nexus: integrated modeling and indices for cumulative impact assessment of farm management practices

Background

Best management practices (BMPs) are promising solutions that can partially control pollution discharged from farmlands. These strategies, like fertilizer reduction and using filter strips, mainly control nutrient (N and P) pollution loads in basins. However, they have secondary impacts on nutrition production and ecosystem. This study develops a method to evaluate the cumulative environmental impacts of BMPs. It also introduces and calculates food's environmental footprint (FEF) for accounting the total environmental damages per nutrition production.

Methods

This study combines the soil and water assessment tool (SWAT) for basin simulation with the indices of ReCiPe, a life cycle impact assessment (LCIA) method. By these means, the effectiveness of BMPs on pollution loads, production yields, and water footprints (WFs) are evaluated and converted as equivalent environmental damages. This method was verified in Zrebar Lake, western Iran. Here, water consumption, as WFs, and eutrophication are the main indices that are converted into equivalent health and ecological impairments. Two methods, entropy and environmental performance index (EPI), are used for weighting normalized endpoints in last step.

Results

Results showed that using 25-50% less fertilizer and water for irrigation combined with vegetated filter strips reduce N and P pollution about 34-60% and 8-21%, respectively. These can decrease ecosystem damages by 5-9% and health risks by 7-14%. Here, freshwater eutrophication is a more critical damage in ecosystem. However, using less fertilizer adversely reduces total nutrition production by 1.7-3.7%. It means that BMPs can decline total ecological damages and health risks, which threatens nutrition production. FEF presents a tool to solve this dilemma about the sustainability of BMPs. In the study area, a 4-9% decrease in FEF means that BMPs are more environmental friendly than nutrition menacing. Finally, this study concludes that SWAT-ReCiPe with FEF provides a quantitative framework for environment-food nexus assessment. However, due to the uncertainties, this method is recommended as a tool for comparing management strategies instead of reporting certain values.

Nutrient released characteristics of struvite-biochar fertilizer produced from concentrated sludge supernatant by fluidized bed reactor

With the exacerbating water eutrophication globally, it is important to recover nitrogen (N) and phosphorus (P) from sewage for recycle. In this study, coconut shell biochar and ethylene diamine tetraacetic acid (EDTA) were added into the designed fluidized bed reactor (FBR) to create struvite-biochar. N and P released from struvite-biochar and the recovery efficiency of N and P from concentrated sludge supernatant were analyzed. Results showed that the optimal operation condition for hydraulic retention time (HRT), pH, Mg/P molar ration, and addition amount EDTA were 90 min, 9.5, 1.2, and 0.2 g/L, respectively. The recovery efficiency of NH₄⁺-N and PO₄^3--P, and purity struvite for FBR were 34.41%-38.05%, 64.95-68.40%, and 84.15%, respectively. The recovery efficiency of NH₄⁺-N and PO₄^3--P were respectively increased by 7.23% and 5.36% when FBR with addition of 0.33 g/L coconut shell biochar, but purity struvite from struvite-biochar decreased by 45.70%. Contents of As, Cd, Pb, and Cr in struvite and struvite-biochar were all lower than Chinese Standard Limits of Fertilizer. Compared to commercial chemical fertilizer, such as superphosphate and urea, struvite-biochar and struvite have slowly released N and P. The amounts of released P, NO₃^--N and NH₄⁺-N from struvite-biochar were higher than struvite during the five leaching times. Compared with struvite, the total amounts of released P, NO₃^--N and NH₄⁺-N from struvite-biochar increased by 4.9%, 3.5% and 8.3%, respectively. Therefore, it is valuable to add biochar into FBR to recovery N and P from concentrated sludge supernatant and make struvite-biochar as a slow-release fertilizer.

Nitrogen and Phosphorus Removal Efficiency and Denitrification Kinetics of Different Substrates in Constructed Wetland

Constructed wetlands (CWs) are generally used for wastewater treatment and removing nitrogen and phosphorus. However, the treatment efficiency of CWs is limited due to the poor performance of various substrates. To find appropriate substrates of CWs for micro-polluted water treatment, zeolite, quartz sand, bio-ceramsite, porous filter, and palygorskite self-assembled composite material (PSM) were used as filtering media to treat slightly polluted water with the aid of autotrophic denitrifying bacteria. PSM exhibited the most remarkable nitrogen and phosphorus removal performance among these substrates. The average removal efficiencies of ammonia nitrogen, total nitrogen, and total phosphorus of PSM were 66.4%, 58.1%, and 85%, respectively. First-order continuous stirred-tank reactor (first-order-CSTR) and Monod continuous stirred-tank reactor (Monod-CSTR) models were established to investigate the kinetic behavior of denitrification nitrogen removal processes using different substrates. Monod-CSTR model was proven to be an accurate model that could simulate nitrate nitrogen removal performance in vertical flow constructed wetland (VFCWs). Moreover, PSM demonstrated significant pollutant removal capacity with the kinetics coefficient of 2.0021 g/m2 d. Hence, PSM can be considered as a promising new type of substrate for micro-polluted wastewater treatment, and Monod-CSTR model can be employed to simulate denitrification processes.

Simultaneous adsorption of ammonia and phosphate using ferric sulfate modified carbon/zeolite composite from coal gasification slag

Removal of nutrients in water is crucial to control eutrophication. Fly ash has been increasingly used to synthesize zeolite to remove nutrients, but it is still poorly understood about the removal capacity of zeolite synthesized from coal gasification slag (CGS), which has not been well recycled in many countries. In this study, the CGS was acid leached, alkali dissolved, and synthesized to carbon/zeolite composite (C/ZC) under induction by medical stone. After being modified by ferric sulfate, the composite was analyzed for the adsorption of NH₄⁺ and PO₄^3-. Results showed that the maximum adsorption capacity by C/ZC is 5.17 mg/g, but C/ZC has no adsorption capacity of PO₄^3-. The ferric sulfate was used to modify C/ZC to obtain carbon/zeolite composite modified by iron (M-C/ZC). M-C/ZC has a higher specific surface area (348.3 m²/g), and the negatively charge of M-C/ZC can adsorb NH₄⁺ and form Fe-O-P between PO₄^3- and Fe-OH bonds. The maximum adsorption capacity of NH₄⁺ and PO₄^3- by M-C/ZC are 7.44 mg/g and 6.94 mg/g, respectively. The removal efficiency of NH₄⁺ and PO₄^3- are up to 88% and 99% under initial NH₄⁺ (5 mg/L) and PO₄^3- (10 mg/L) concentration. The regeneration capacity of M-C/ZC of NH₄⁺ was stronger than that of PO₄^3-. After three cycles, the regeneration rate of M-C/ZC of NH₄⁺ was still up to 76.96%. Our findings suggest the good application potential of M-C/ZC for removing NH₄⁺ and PO₄^3- from wastewater.

Differential efficacy of water lily cultivars in phytoremediation of eutrophic water contaminated with phosphorus and nitrogen

Excessive inputs of phosphorus (P) and nitrogen (N) trigger eutrophication of the water bodies, which promotes the undesirable growth of algal bloom and deterioration of the water quality, and aquatic biodiversity. Macrophytes provide an environmentally benign and economically viable paradigm for the ecological restoration of eutrophic aquatic ecosystems. Water lily (Nymphaea) is largely used as ornamental plant for landscaping, and it has been documented that water lily possesses the potentiality in mitigating polluted aquatic environments. In the present study, water lily cultivars Nymphaea Texas Dawn (NTD), Nymphaea Colorado (NC), Nymphaea Madame Wilfron Gonnère (NMWG), and Nymphaea Sunshine Princess (NSP) were investigated for their potency in alleviating the eutrophication. The concentrations of total P and total N were significantly higher in the leaves of NC and NSP compared with NTD and NMWG. Therefore, NC and NSP were selected for subsequent studies to decipher their recuperation efficacy on eutrophic waters at different growth stages. NC and NSP significantly reduced the concentrations of eutrophication indicators i.e., total P, NH₄⁺-N, and chemical oxygen demand in different gradients of the simulated eutrophic water in a growth-dependent manner. On the contrary, NC and NSP triggered a significant increase in the concentration of dissolved oxygen particularly at the seedling stage. Notably, the concentrations of total P (shoot and root) and total N (root) were relatively higher in NSP than NC. The study thus revealed a growth-dependent differential efficacy of NSP and NC in mitigating the different eutrophic waters.

Beyond Bioextraction: The Role of Oyster-Mediated Denitrification in Nutrient Management

Recently, interest has grown in using oyster-mediated denitrification resulting from aquaculture and restoration as mechanisms for reactive nitrogen (N) removal. To date, short-term N removal through bioextraction has received the most management interest, but there is a growing body of research that has shown oysters can also mediate the long-term removal of N through denitrification (the microbial conversion of reactive N to relatively inert dinitrogen (N₂) gas). Oyster suspension feeding and ammonium release via waste and deposition of organic matter to the sediments can stimulate nitrification-denitrification near oyster reefs and aquaculture sites. Oysters also harbor a diverse microbial community in their tissue and shell promoting denitrification and thus enhanced N removal. Additionally, surface areas on oyster reefs provide a habitat for other filter-feeding macrofaunal communities that can further enhance denitrification. Denitrification is a complex biogeochemical process that can be difficult to convey to stakeholders. These complexities have limited consideration and inclusion of oyster-mediated denitrification within nutrient management. Although oyster-mediated denitrification will not be a standalone solution to excess N loading, it may provide an additional management tool that can leverage oyster aquaculture and habitat restoration as a N mitigation strategy. Here, we provide an overview of the biogeochemical processes involved in oyster-mediated denitrification and summarize how it could be incorporated into nutrient management efforts by various stakeholders.

Wetland Restoration with Hydrophytes: A Review

Restoration cases with hydrophytes (those which develop all their vital functions inside the water or very close to the water surface, e.g., flowering) are less abundant compared to those using emergent plants. Here, I synthesize the latest knowledge in wetland restoration based on revegetation with hydrophytes and stress common challenges and potential solutions. The review mainly focusses on natural wetlands but also includes information about naturalized constructed wetlands, which nowadays are being used not only to improve water quality but also to increase biodiversity. Available publications, peer-reviewed and any public domain, from the last 20 years, were reviewed. Several countries developed pilot case-studies and field-scale projects with more or less success, the large-scale ones being less frequent. Using floating species is less generalized than submerged species. Sediment transfer is more adequate for temporary wetlands. Hydrophyte revegetation as a restoration tool could be improved by selecting suitable wetlands, increasing focus on species biology and ecology, choosing the suitable propagation and revegetation techniques (seeding, planting). The clear negative factors which prevent the revegetation success (herbivory, microalgae, filamentous green algae, water and sediment composition) have to be considered. Policy-making and wetland restoration practices must more effectively integrate the information already known, particularly under future climatic scenarios.