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Subsurface-flow constructed wetlands (SSF CWs), which include horizontal subsurface–flow constructed wetlands (HSSF CWs) and vertical subsurface–flow constructed wetlands (VSSF CWs), have become increasingly popular for the treatment of various waste streams such as wastewater, landfill leachate, and stormwater runoff. These wetlands utilize a variety of natural physical, chemical, and microbial processes to effectively remove contaminants. This article aims to provide valuable insights into the application of subsurface-flow wetlands for the treatment of stormwater runoff by collecting and reviewing relevant articles. Within the realm of stormwater contaminants, this review primarily focuses on nutrients, heavy metal, and per- and polyfluoroalkyl substances (PFAS), which are commonly found in stormwater runoff worldwide. The removal percentages of these contaminants vary across different studies, depending on factors such as the characteristics of the contaminants, the type and scale of the subsurface-flow wetland, as well as the selection of plants and substrates used. This study provides valuable insights into the various processes that significantly contribute to the removal of contaminants, including adsorption, plant uptake, and biodegradation. The removal percentage of PFAS ranges from 1% to 99% in constructed wetlands. The wide range of PFAS removal comes from differences between PFAS category, plant and soil type, wetland configuration, and matrix effects. Additionally, this paper brings attention to the current gaps and limitations present in the research conducted within this field. It is imperative to conduct further studies utilizing real-world or synthetic stormwater runoff to deepen our comprehension in this domain. Furthermore, considering that each category of PFAS possesses unique properties, conducting individual studies on each group becomes crucial to attain a comprehensive understanding of the behavior and transformation of PFAS in CWs. [ABSTRACT FROM AUTHOR]

Cities worldwide face resilience challenges as climate risks interact with rapid urbanization, loss of biodiversity and ecosystem services, poverty, and Socioeconomic inequality. This leads to the social, physical, and economic collapse of cities and their systems. Over time, urban resilience challenges are expected to increase, driven by urbanization, land use, and climate change. It is for this reason that the concept of urban resilience is increasingly attracting the attention of governments, and urban planners. Gray infrastructure is not always suitable for profitability, resilience, or sustainability. Now more than ever, green infrastructure is recognized as a nature-based solution (NBS) that plays a significant role in addressing resilience challenges in urban areas. These solutions can be applied through spatial measurements and parameters in and around the city. Constructed wetlands (Cws) are artificial imitations of natural wetlands, one of the most biologically diverse natural ecosystems, and in addition to aesthetics, It provides an effective model for resilient environmental engineering solutions as a low-cost and easy-to-operate alternative to traditional urban management systems. Consequently, the main objective of this research was to define criteria for integrating constructed wetlands (Cws) into the urban landscape as nature-based solutions (NBS) and address the limitations and maximize advantages as well as contribute to replicate best practices of constructed wetlands (Cws) in different Zones (Desert, River's floodplain, coastal) in Egyptian cities for enhancing the urban resilience. [ABSTRACT FROM AUTHOR]

Sanjiang Plain is intensively used for rice production, and ditch drainage diffuse pollution prevention is crucial. Groundwater, rich in Fe ions, is the main source of irrigation water in this region. In this study, pyrite and zero-valent iron (ZVI) (sponge iron and iron scraps) were used as substrates to identify the synergistic influence of exogenous Fe2+ addition and solid iron substrates on pollutant removal in constructed wetlands. Based on the results, iron substrates hardly improved the ammonia removal, mainly because of the physical structure and oxidation activity. At a hydraulic retention time longer than 8 h, the pollution removal efficiency in the zero-valent iron (ZVI) substrate treatment increased significantly, and the removal of nitrate (NO3−-N) and total phosphorus (TP) in the iron scrap substrate treatment reached about 60% and 70%, respectively. The high-throughput sequencing results showed a significant increase in the abundance of microorganisms involved in denitrification and phosphate accumulation in biofilms on ZVI substrates. The highest diversities of such microorganisms in biofilms on iron scraps were found for denitrifying bacteria (Pseudomonas), nitrate-reducing Fe (II)-oxidizing bacteria (Acidovorax), and Dechloromonas with autotrophic denitrification and phosphate accumulation, with a 43% cumulative abundance. Dechloromonas dominated in the iron sponge substrate treatment. The highest relative abundance of Acidovorax was found in the mixed iron substrate (pyrite, sponge iron, and iron scraps) treatment. The addition of ZVI substrate significantly improved the removal of NO3−-N and TP and reduced the hydraulic retention time through the continuous release of Fe2+ and the promotion of microbial growth. When designing constructed wetlands for treating paddy field drainage, the appropriate addition of iron scrap substrates is recommended to enhance the pollutant removal efficiency and shock load resistance of CWs.

Macrophytes have the potential to withstand pollutant-induced stress and can be used to clean contaminated water using phyto-extraction, phyto-degradation, phyto-filtration, phyto-stimulation, and phyto-volatilization technique(s). Phytoremediation through constructed wetlands (CWs) for eliminating inorganic and organic pollutants from household sewage and wastewater has attracted scientific attention. CWs are artificially engineered treatment systems that utilize natural cycles or processes involving soils, wetland vegetation, and plant and soil-associated microbial assemblages to remediate contaminated water and improve its quality. Herein, we present a detailed assessment of contaminant removal effectiveness in different CW systems, i.e., free-water surface or surface-flow constructed wetlands (FWSCWs/SFCWs), subsurface-flow constructed wetlands (SSFCWs), and hybrid constructed wetlands (HCWs). Several wetland floral species have been reported as potential phytoremediators, effectively reducing aquatic contamination through biodegrading, biotransforming, and bioaccumulating contaminants. Water hyacinth (Pontederia crassipes) is one of the most resistant macrophytes, capable of tolerating high nitrate (NO3−) and phosphate (PO42−) concentrations. Other aquatic weeds also effectively alleviate biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), and pathogen levels and ameliorate the impact of different ionic forms of nitrogen (N), phosphorus (P), and trace elements (TEs). The review primarily focuses on using hydrophyte(s)-microbe(s) associations in different CWs as an essential phytoremediation tool for sustainable management of freshwater ecosystems, ecorestoration, and prospective resource recovery, favoring a circular bioeconomy (CBE). [ABSTRACT FROM AUTHOR]

The development of industry has caused metal pollution of aquatic ecosystems and water deterioration worldwide. Therefore, environmentally friendly strategies for industrial wastewater treatment are needed. In this study, constructed wetlands (CWs) were planted with Schoenoplectus californicus in a culture medium with different concentrations of Cu, Pb, and Zn. The aims of this work were to evaluate the ability of S. californicus to accumulate Cu, Pb, and Zn and its physiological response to metal exposure, and assess the wastewater treatment performance of the CW systems. The accumulation of Cu, Pb, and Zn in the shoot and root of the emergent aquatic plant depended on the metal concentration during the 28 days of exposure, except for Pb in shoots. The bioconcentration factors of Cu (46.7±10.8) and Zn (896±317) were highest in the treatment with moderate levels of metals (T-2), whereas for Pb (57.4±15.9), the maximum bioconcentration factor was recorded in the treatment with the highest metal levels (T-3). Metal translocation from root to shoot reached values greater than 1 for Cu, but were lower for Pb and Zn because accumulation occurred predominantly in the root. In general, the removal efficiency of the CW systems was higher than 90% for Pb and Zn, and higher than 80% for Cu. Furthermore, Cu, Pb, and Zn bioaccumulation in S. californicus did not reflect toxicological damage to physiological parameters, such as the formation of products of lipid membrane peroxidation. The results showed that the exposure to relatively high metal concentrations in the CWs did not affect the survival of the species. Considering the capacity of S. californicus to tolerate and accumulate Pb, Zn, and Cu, this species can be used as a phytoextractor in wastewater treatment in CW systems. [ABSTRACT FROM AUTHOR]

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Macrophytes have the potential to withstand pollutant-induced stress and can be used to clean contaminated water using phyto-extraction, phyto-degradation, phyto-filtration, phyto-stimulation, and phyto-volatilization technique(s). Phytoremediation through constructed wetlands (CWs) for eliminating inorganic and organic pollutants from household sewage and wastewater has attracted scientific attention. CWs are artificially engineered treatment systems that utilize natural cycles or processes involving soils, wetland vegetation, and plant and soil-associated microbial assemblages to remediate contaminated water and improve its quality. Herein, we present a detailed assessment of contaminant removal effectiveness in different CW systems, i.e., free-water surface or surface-flow constructed wetlands (FWSCWs/SFCWs), subsurface-flow constructed wetlands (SSFCWs), and hybrid constructed wetlands (HCWs). Several wetland floral species have been reported as potential phytoremediators, effectively reducing aquatic contamination through biodegrading, biotransforming, and bioaccumulating contaminants. Water hyacinth (Pontederia crassipes) is one of the most resistant macrophytes, capable of tolerating high nitrate (NO3−) and phosphate (PO42−) concentrations. Other aquatic weeds also effectively alleviate biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), and pathogen levels and ameliorate the impact of different ionic forms of nitrogen (N), phosphorus (P), and trace elements (TEs). The review primarily focuses on using hydrophyte(s)-microbe(s) associations in different CWs as an essential phytoremediation tool for sustainable management of freshwater ecosystems, ecorestoration, and prospective resource recovery, favoring a circular bioeconomy (CBE).

The presence of emerging contaminants (ECs) in the environment, especially in the water and wastewater matrices, has become a major headache for the competent authorities, because even with the mildest of exposure aquatic organisms, as well as humans, can exhibit chronic/acute toxicity. In the last few years constructed wetlands (CWs) have become a popular method to eradicate ECs from water and wastewater, because they are an environmentally benevolent, economically feasible, and aquatic plant-based natural technology. However, information is not readily available on how to configure a CW (or combination of CWs, for hybrid CWs) to ensure the substantial removal of ECs. Thus, the present review analyzes how the various physicochemical properties of ECs govern their major removal pathways in different CWs and how the design configuration of a CW can lead to better EC removal. Finally, some recommendations regarding the possible configuration or combination of CWs on the basis of the ECs' known physicochemical properties are made. This review article will help in selecting the proper combinations of CWs to eliminate the ECs of concern (known or unknown) from the aquatic matrices. [ABSTRACT FROM AUTHOR]

Microbial source tracking (MST) has been recognised as an effective tool for determining the origins and sources of faecal contamination in various terrestrial and aquatic ecosystems. Thus, it has been widely applied in environmental DNA (eDNA) surveys to define specific animal- and human-associated faecal eDNA. In this context, identification of and differentiation between anthropogenic and zoogenic faecal pollution origins and sources are pivotal for the evaluation of waterborne microbial contamination transport and the associated human, animal, and environmental health risks. These concerns are particularly pertinent to diverse nature-based solutions (NBS) that are being applied specifically to secure water safety and human and ecosystem well-being, for example, constructed wetlands (CWs) for water and wastewater treatment. The research in this area has undergone a constant evolution, and there is a solid foundation of publications available across the world. Hence, there is an early opportunity to synthesise valuable information and relevant knowledge on this specific topic, which will greatly benefit future work by improving NBS design and performance. By selecting 15 representative research reports published over 20 years, we review the current state of MST technology applied for faecal-associated contamination measures in NBS/CWs throughout the world. [Display omitted] • Microbial source tracking (MST) identifies faecal pollution origins and sources. • MST defines host-specific genetic signatures of faecal environmental DNA (eDNA). • Anthropo-zoogenic sources of faecal eDNA impair water quality and safety. • MST supports (waste)water treatment assessment of nature-based solutions (NBS). [ABSTRACT FROM AUTHOR]

Water scarcity, affecting one-fifth of the global population, is exacerbated by industrial, agricultural, and population growth pressures on water resources. Wastewater, containing Contaminants of Emerging Concern (CECs) such as antibiotics, presents environmental and health hazards. This study explores a Nature-Based Solution (NBS) using Constructed Wetlands (CWs) for wastewater reclamation and CECs removal. Two CW configurations (Vertical-VCW and Hybrid-HCW) were tested for their efficacy. Results show significant reduction in for all the chemico-physical and biological parameters meeting Italian water reuse standards. Furthermore, Antibiotic Resistant Bacteria (ARB) and Antibiotic Resistant Genes (ARGs) were effectively reduced, emphasizing the potential of the CWs in mitigating Antimicrobial Resistance (AMR). Lettuce seedlings irrigated with the treated wastewater exhibited no ARB/ARGs transfer, indicating the safety of the reclaimed wastewater for agricultural use. Overall, CWs emerge as sustainable Nature Based Solutions (NBS) for wastewater treatment, contributing to global water conservation efforts amid escalating water scarcity challenges. [Display omitted] • Global water scarcity tackled with CWs. • CWs meet Italian reuse standards. • Effective ARB/ARGs reduction in CWs. • Safe CW-treated water for agriculture. • No trace of AMR in lettuce leaves. [ABSTRACT FROM AUTHOR]

A METland is an innovative treatment wetland (TW) that relies on the stimulation of electroactive bacteria (EAB) to enhance the degradation of pollutants. The METland is designed in a short-circuit mode (in the absence of an external circuit) using an electroconductive bed capable of accepting electrons from the microbial metabolism of pollutants. Although METlands are proven to be highly efficient in removing organic pollutants, the study of in situ EAB activity in full-scale systems is a challenge due to the absence of a two-electrode configuration. For the first time, four independent full-scale METland systems were tested for the removal of organic pollutants and nutrients, establishing a correlation with the electroactive response generated by the presence of EAB. The removal efficiency of the systems was enhanced by plants and mixed oxic–anoxic conditions, with an average removal of 56 g of chemical oxygen demand (COD) mbed material–3 day–1 and 2 g of total nitrogen (TN) mbed material–3 day–1 for Ørby 2 (partially saturated system). The estimated electron current density (J) provides evidence of the presence of EAB and its relationship with the removal of organic matter. The tested METland systems reached the max. values of 188.14 mA m–2 (planted system; IMDEA 1), 223.84 mA m–2 (non-planted system; IMDEA 2), 125.96 mA m–2 (full saturated system; Ørby 1), and 123.01 mA m–2 (partially saturated system; Ørby 2). These electron flow values were remarkable for systems that were not designed for energy harvesting and unequivocally show how electrons circulate even in the absence of a two-electrode system. The relation between organic load rate (OLR) at the inlet and coulombic efficiency (CE; %) showed a decreasing trend, with values ranging from 8.8 to 53% (OLR from 2.0 to 16.4 g COD m–2 day–1) for IMDEA systems and from 0.8 to 2.5% (OLR from 41.9 to 45.6 g COD m–2 day–1) for Ørby systems. This pattern denotes that the treatment of complex mixtures such as real wastewater with high and variable OLR should not necessarily result in high CE values. METland technology was validated as an innovative and efficient solution for treating wastewater for decentralized locations. [ABSTRACT FROM AUTHOR]

A METland is an innovative treatment wetland (TW) that relies on the stimulation of electroactive bacteria (EAB) to enhance the degradation of pollutants. The METland is designed in a short-circuit mode (in the absence of an external circuit) using an electroconductive bed capable of accepting electrons from the microbial metabolism of pollutants. Although METlands are proven to be highly efficient in removing organic pollutants, the study of in situ EAB activity in full-scale systems is a challenge due to the absence of a two-electrode configuration. For the first time, four independent full-scale METland systems were tested for the removal of organic pollutants and nutrients, establishing a correlation with the electroactive response generated by the presence of EAB. The removal efficiency of the systems was enhanced by plants and mixed oxic–anoxic conditions, with an average removal of 56 g of chemical oxygen demand (COD) mbed material–3 day–1 and 2 g of total nitrogen (TN) mbed material–3 day–1 for Ørby 2 (partially saturated system). The estimated electron current density (J) provides evidence of the presence of EAB and its relationship with the removal of organic matter. The tested METland systems reached the max. values of 188.14 mA m–2 (planted system; IMDEA 1), 223.84 mA m–2 (non-planted system; IMDEA 2), 125.96 mA m–2 (full saturated system; Ørby 1), and 123.01 mA m–2 (partially saturated system; Ørby 2). These electron flow values were remarkable for systems that were not designed for energy harvesting and unequivocally show how electrons circulate even in the absence of a two-electrode system. The relation between organic load rate (OLR) at the inlet and coulombic efficiency (CE; %) showed a decreasing trend, with values ranging from 8.8 to 53% (OLR from 2.0 to 16.4 g COD m–2 day–1) for IMDEA systems and from 0.8 to 2.5% (OLR from 41.9 to 45.6 g COD m–2 day–1) for Ørby systems. This pattern denotes that the treatment of complex mixtures such as real wastewater with high and variable OLR should not necessarily result in high CE values. METland technology was validated as an innovative and efficient solution for treating wastewater for decentralized locations.

The discharge of city tail water in China has aggravated the pollution of rivers, lakes, and groundwater. Compared with other methods, ecological treatment has advantages in cost and effect. Based on the review of literature, the water quality of city tail water in China was analyzed, and the treatment of city tail water by constructed wetlands (CWs), ecological pond, and ecological floating bed (EFB) was discussed. The pollution indicator concentration of city tail water is higher than that of class IV water standards for rivers and lakes. The maximum removal rates of NH4+-N, TP, and TN in city tail water by CWs are more than 85%. The EFB technology plays an important role in the treatment process of city tail water, and the proportion of substrate treatment is higher in substrate, plant, and microorganism. The economic value of plant is also an important issue to be considered in EFB treatment of city tail water. There are many researches on the single technology of EFB, CWs, and ecological pond for the treatment of city tail water, but the comprehensive technology research of two or more is lacking. This study is of great significance to promote the ecological treatment of city tail water. [ABSTRACT FROM AUTHOR]

: (1) Phosphorus (P) is an essential plant nutrient, and P deficiency negatively affects plant growth and development. Furthermore, P is a finite and nonrenewable resource, and there is an urgent need to recover P from some of the important waste streams in society. Newly engineered calcareous materials (sol–gel coated cat litter (CATSAN®)) can bind P from wastewater in decentralized treatment systems and potentially enable P recycling into agricultural production by direct addition of the P saturated material. (2) The effects of the addition of two P-enriched calcareous materials as fertilizers for maize (Zea mays L.) growth were investigated in a mesocosm experiment. We compared fertilization with the P-enriched materials at rates of 6, 12, 25, 50, 100 kg P ha−1 yr−1 with fertilization with commercial NPK fertilizer. (3) The P fertilization by the P-enriched materials had a significant positive effect on plant height, biomass, maximum light-saturated photosynthetic rate, respiration rate, and total P content in biomass. However, plants fertilized by the commercial NPK fertilizer performed significantly better in the majority of measured parameters at identical fertilization rates. (4) The bioavailability of the P bound to the calcareous material was very low. However, the studied material has the potential to be used as part of a decentralized treatment solution to remove and subsequently recover and recycle P from wastewater. [ABSTRACT FROM AUTHOR]

(1) Phosphorus (P) removal has proven difficult in decentralized wastewater treatment systems, and P binding material, installed as an external filter, has been proposed for improving P removal. Especially, calcium (Ca)-rich materials have shown promising results. (2) Five calcareous materials were tested with isotherm batch experiments. The material with the highest P adsorption capacity was selected to undergo different Sol-Gel coatings, i.e., different coating dilution ratios (1:10, 1:5, and 1:1) and exposure periods (5, 10, and 15 min). The seven coated materials were evaluated by isotherm experiments. (3) The maximum adsorption capacity (Qmax) was determined by fitting the Langmuir equation. Qmax for the non-coated materials, and ranged from 0.7 (sand) to 35.1 (Catsan) mg P g−1 DW, while the coated materials ranged from 7.8 to 24.7 mg P g−1 DW depending on the coating. Based on the rotated Principal Component Analysis, the most important parameters for Qmax were the texture and the Ca content. (4) Catsan was the most promising material, but when performing a Sol-Gel coating, a trade-off between preserving Qmax and the coating thickness were evident, as the materials with the thinner coating preserved more of the sorption capacity. The development of P binding materials constitutes a useful technology in decentralized wastewater treatment systems.

Antibiotic resistance is a growing problem worldwide. The emergence and rapid spread of antibiotic resistance determinants have led to an increasing concern about the potential environmental and public health endangering. Wastewater treatment plants (WWTPs) play an important role in this phenomenon since antibacterial drugs introduced into wastewater can exert a selection pressure on antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Therefore, WWTPs are perceived as the main sources of antibiotics, ARB and ARG spread in various environmental components. Furthermore, technological processes used in WWTPs and its exploitation conditions may influence the effectiveness of antibiotic resistance determinants’ elimination. The main aim of the present study was to compare the occurrence of selected tetracycline and sulfonamide resistance genes in raw influent and final effluent samples from two WWTPs different in terms of size and applied biological wastewater treatment processes (conventional activated sludge (AS)-based and combining a conventional AS-based method with constructed wetlands (CWs)). All 13 selected ARGs were detected in raw influent and final effluent samples from both WWTPs. Significant ARG enrichment, especially for tet(B, K, L, O) and sulIII genes, was observed in conventional WWTP. The obtained data did not show a clear trend in seasonal fluctuations in the abundance of selected resistance genes in wastewaters.

Over the past few decades, low phosphorus removal efficiency hampered the further application of constructed wetlands (CWs). In this study, magnesium (Mg)-containing materials, i.e., magnesia and magnesite, were added into CWs substrate to improve TP removal performance. Results showed that the average TP removal efficiency of magnesia group (MA-CW) reached 93.3%, which was 17.5% and 18.6% higher than that of magnesite group (ME-CW) and control group (QZ-CW), respectively. P fractionation analysis showed that the proportion of phosphorus sequestration by substrate in MA-CW was 90.4%, while it was only 65.1% and 58.8% in ME-CW and QZ-CW, respectively. Phosphorus assimilation by plant in ME-CW accounted for 9.52%, higher than other groups, which was attributed to the stimulated plant growth caused by Mg addition. The average total chlorophyll content of plants in ME-CW was 4.61 mg g −1 FW during the study period and the plant growth rate was superior to other groups, whereas in MA-CW, excessive alkaline (pH = 10.29) caused by MgO dissolution depressed plant growth. Mg addition also elevated the absolute abundance of (PAOs), which followed the order of MA-CW (1.76 ± 0.03 × 10 7  copies g −1 ) > ME-CW (1.35 ± 0.02×10 7 copies g −1 ) > QZ-CW (4.48 ± 0.13 × 10 6  copies g −1 ). Characterization of magnesia and magnesite before and after phosphate adsorption was compared and the results indicated that phosphorus adsorption by magnesium mainly relied on co-precipitation of Mg 3 (PO 4 ) 2 and MgHPO 4 , as well as ligand-exchange on the surface. [ABSTRACT FROM AUTHOR]

Polder watercourses within agricultural areas are affected by high chemical oxygen demand (COD) and biological oxygen demand (BOD5) concentrations, due to intensive farming activities and runoff. Practical cases have shown that constructed wetlands (CWs) are eco-friendly and cost-effective treatment systems which can reduce high levels of organic and nutrient pollution from agricultural discharges. However, accumulated recalcitrant organic matter, originated by in-situ sources or elements of CWs (i.e., plants or microbial detritus), limits the fulfilment of current COD discharge threshold. Thus, to evaluate its relevance regarding rivers ecosystem health preservation, we analysed the response of bio-indicators, the Multimetric Macroinvertebrate Index Flanders (MMIF) and the occurrence of organic pollution sensitive taxa towards organic pollutants. For this purpose, statistical models were developed based on collected data in polder watercourses and CWs located in Flanders (Belgium). Results showed that, given the correlation between COD and BOD5, both parameters can be used to indicate the ecological and water quality conditions. However, the variability of the MMIF and the occurrence of sensitive species are explained better by BOD5, which captures a major part of their common effect. Whereas, recalcitrant COD and the interaction among other physico-chemical variables indicate a minor variability on the bio-indicators. Based on these outcomes we suggest a critical re-evaluation of current COD thresholds and moreover, consider other emerging technologies determining organic pollution levels, since this could support the feasibility of the implementation of CWs to tackle agricultural pollution. [ABSTRACT FROM AUTHOR]

Landfill leachate could be a significant source of emerging contaminants (ECs) and antibiotic resistance genes (ARGs) into the environment. This study provides the first information on the occurrence of selected ECs and ARGs in raw leachate from 16-year old closed landfill site in Singapore. Among the investigated ECs, acetaminophen (ACT), bisphenol A (BPA), clofibric acid (CA), caffeine (CF), crotamiton (CTMT), diclofenac (DCF), N , N -diethyl-m-toluamide (DEET), gemfibrozil (GFZ), lincomycin (LIN), salicylic acid (SA), and sulfamethazine (SMZ) were the most frequently detected compounds in raw landfill leachate. The concentrations of detected ECs in raw landfill leachate varied significantly, from below quantification limit to 473,977 ng/L, depending on the compound. In this study, Class I integron ( intl1 ) gene and ten ARGs were detected in raw landfill leachate. Sulfonamide resistance ( sul1, sul2, and dfrA ), aminoglycoside resistance ( aac6 ), tetracycline resistance ( tetO ), quinolone resistance ( qnrA ), and intl1 were ubiquitously present in raw landfill leachate. Other resistance genes, such as beta-lactam resistance ( blaNMD1 , blaKPC , and blaCTX ) and macrolide-lincosamide resistance ( ermB ) were also detected, detection frequency of <50%. The removal of target ECs and ARGs by a full-scale hybrid constructed wetland (CW) was also evaluated. The vast majority of ECs exhibited excellent removal efficiencies (>90%) in the investigated hybrid CW system. This hybrid CW system was also found to be effective in the reduction of several ARGs ( intl1 , sul1 , sul2 , and qnrA ). Aeration lagoons and reed beds appeared to be the most important treatment units of the hybrid CW for removing the majority of ECs from the leachate. [ABSTRACT FROM AUTHOR]

Plants and microorganisms are the main biotic compartments for phytoaccumulation and metabolic transformation of organic contaminants in constructed wetlands (CWs). However, how they cope with special pollutants during the treatment process has not been well characterized. In this study, responses of Iris pseudoacorus (I. pseudoacorus) and microbial communities were intensively investigated in pilot-scale CWs treating wastewater-borne chlorpyrifos, an organic phosphorus pesticide. Chlorpyrifos was associated with inhibited plant growth, decreased photosynthetic activity, and a significant increase in oxidative products. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities were affected by chlorpyrifos, whereas catalase (CAT) activity was almost unaffected. Although chlorpyrifos stimulated the antioxidant system, there was little indication of oxidative damage in I. pseudoacorus. Urease, β-glucosidase, and phosphatase activities in substrate were elevated by 73.73%, 17.20%, and 16.23%, respectively, which may indicate enhancement of nitrogen, carbon, and phosphorus cycling. Fatty acid methyl ester (FAME) profiles showed that aerobic prokaryotes, which are likely the functional group responsible for chlorpyrifos degradation, increased from 16.37% to 31.32% after chlorpyrifos addition. Biomarkers for fungal/bact and trans/cis remained unchanged after the chlorpyrifos addition, suggesting that chlorpyrifos did not negatively influence the substrate microbial communities in CWs. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) are regarded as a risk mitigation strategy for alleviating the risks associated with agricultural runoff that contains pesticides. We investigated the partitioning pattern of wastewater-borne chlorpyrifos, a widely used organophosphorus pesticide, in non-vegetated and vegetated CWs. Removal rates of chlorpyrifos calculated from inflow and outflow concentrations ranged from 87.65% to 96.57%. The average removal rate was significantly higher and more stable in vegetated CWs than in non-vegetated CWs. As determined using a mass-balance method, outflows, macrophytes, substrate micro-degradation, and "other" accounted for 5.23%, 22.7%, 15.96%, and 56.11%, respectively, of the chlorpyrifos in the vegetated system. Of all Iris pseudoacorus organs examined, the rhizome was dominant in biomass and gathered the largest amount of chlorpyrifos. Except for the uptake of chlorpyrifos by plants, the primary difference between vegetated and non-vegetated CWs was that there was a relatively low potential for chlorpyrifos micro-degradation and volatilization and photolysis in vegetated CWs than in non-vegetated CWs. Identification of this partitioning pattern elucidates the mechanisms underlying chlorpyrifos removal from wastewater in CWs. [ABSTRACT FROM AUTHOR]

The demand for seafood products on the global market is rising, particularly in Asia, as affluence and appreciation of the health benefits of seafood increase. This is coupled with a capture fishery that, at best, is set for stagnation and, at worst, significant collapse. Global aquaculture is the fastest growing sector of the food industry and currently accounts for approximately 45.6% of the world's fish consumption. However, the rapid development of extensive and semi-extensive systems, particularly intensive marine-fed aquaculture, has resulted in worldwide concern about the potential environmental, economic, and social impacts of such systems. In recent years, there has been a significant amount of research conducted on the development of sustainable saltwater-based food production systems through mechanical (e.g., recirculatory aquaculture (RAS) systems) methods and ecosystem-based approaches (e.g., integrated multi-trophic aquaculture (IMTA)). This review article will examine the potential negative impacts of monocultural saltwater aquaculture operations and review established (RAS) and novel (IMTA; constructed wetlands; saltwater aquaponics) saltwater-based food production systems and discuss their (potential) contribution to the development of sustainable and environmentally-friendly systems. [ABSTRACT FROM AUTHOR]

Polder watercourses within agricultural areas are affected by high chemical oxygen demand (COD) and biological oxygen demand (BOD5) concentrations, due to intensive farming activities and runoff. Practical cases have shown that constructed wetlands (CWs) are eco-friendly and cost-effective treatment systems which can reduce high levels of organic and nutrient pollution from agricultural discharges. However, accumulated recalcitrant organic matter, originated by in-situ sources or elements of CWs (i.e., plants or microbial detritus), limits the fulfilment of current COD discharge threshold. Thus, to evaluate its relevance regarding rivers ecosystem health preservation, we analysed the response of bio-indicators, the Multimetric Macroinvertebrate Index Flanders (MMIF) and the occurrence of organic pollution sensitive taxa towards organic pollutants. For this purpose, statistical models were developed based on collected data in polder watercourses and CWs located in Flanders (Belgium). Results showed that, given the correlation between COD and BOD5, both parameters can be used to indicate the ecological and water quality conditions. However, the variability of the MMIF and the occurrence of sensitive species are explained better by BOD5, which captures a major part of their common effect. Whereas, recalcitrant COD and the interaction among other physico-chemical variables indicate a minor variability on the bio-indicators. Based on these outcomes we suggest a critical re-evaluation of current COD thresholds and moreover, consider other emerging technologies determining organic pollution levels, since this could support the feasibility of the implementation of CWs to tackle agricultural pollution.

The purpose of wastewater treatment is water reuse. It reduces potable water consumption while preventing fresh water contamination. Water reuse schemes have already been successfully established in different locations. Treatments using constructed wetlands are widely studied as a more economical and environmentally-friendly alternative for treating wastewater. In these systems, the control of inorganic species is also important. This study monitored cations (Na+ , K+ , Li+ and NH4 + ) and anions (SO4 2-, NO3 - , NO2 - , Cl- and PO4 3-) in a constructed wetlands (CWs) system, a rainwater catchment system, sewage treatment system, and in fi nal reuse water. The monitoring was accomplished using ion chromatographic analysis. The removal values found in the CWs were: 99.9% K+ , NH4 + and SO4 2-, 52.6% Na+ , 89.8% NO3 - , 98.2% NO2 - , 63.6% Cl- and 96.8% PO4 3-. The results also showed that CWs system is suitable for removing ions from the wastewater.

In this study, a self-supplying carbon source constructed wetland (CW) was developed and evaluated. Both the effects of plants ( Typha latifolia ) and plant fermentation broth on nitrate removal were measured. The results showed that the addition of plant fermentation broth greatly improved the nitrate removal rate. As the ratio of added chemical oxygen demand to influent nitrate (COD Add /NO 3 -N ratio) increased from 0 to 3, the nitrate removal rate attributed to the plants increased from 0.09 to 0.29 g N m −3 d −1 , but the proportion of total nitrate removal decreased from 27.3% to 10.7%, and denitrification was always the dominant nitrate removal mechanism. Furthermore, there were strong positive correlations between the COD Add /NO 3 -N ratio and the nitrate removal rate, both in unplanted ( R 2 = 0.977) and planted ( R 2 = 0.996) microcosms. Plant biomass could potentially support a nitrate removal rate of 0.05–0.54 g N m −2 d −1 in self-supplying carbon source CWs. [ABSTRACT FROM AUTHOR]

The demand for seafood products on the global market is rising, particularly in Asia, as affluence and appreciation of the health benefits of seafood increase. This is coupled with a capture fishery that, at best, is set for stagnation and, at worst, significant collapse. Global aquaculture is the fastest growing sector of the food industry and currently accounts for approximately 45.6% of the world’s fish consumption. However, the rapid development of extensive and semi-extensive systems, particularly intensive marine-fed aquaculture, has resulted in worldwide concern about the potential environmental, economic, and social impacts of such systems. In recent years, there has been a significant amount of research conducted on the development of sustainable saltwater-based food production systems through mechanical (e.g., recirculatory aquaculture (RAS) systems) methods and ecosystem-based approaches (e.g., integrated multi-trophic aquaculture (IMTA)). This review article will examine the potential negative impacts of monocultural saltwater aquaculture operations and review established (RAS) and novel (IMTA; constructed wetlands; saltwater aquaponics) saltwater-based food production systems and discuss their (potential) contribution to the development of sustainable and environmentally-friendly systems.

The purpose of wastewater treatment is water reuse. It reduces potable water consumption while preventing fresh water contamination. Water reuse schemes have already been successfully established in different locations. Treatments using constructed wetlands are widely studied as a more economical and environmentally-friendly alternative for treating wastewater. In these systems, the control of inorganic species is also important. This study monitored cations (Na+, K+, Li+ and NH4+) and anions (SO42-, NO3-, NO2-, Cl- and PO43-) in a constructed wetlands (CWs) system, a rainwater catchment system, sewage treatment system, and in final reuse water. The monitoring was accomplished using ion chromatographic analysis. The removal values found in the CWs were: 99.9% K+, NH4+ and SO42-, 52.6% Na+, 89.8% NO3-, 98.2% NO2-, 63.6% Cl- and 96.8% PO43-. The results also showed that CWs system is suitable for removing ions from the wastewater. [ABSTRACT FROM AUTHOR]

In this study, effects of aeration and wastewater composition were evaluated on the clogging process in four laboratory-scale wavy subsurface-flow and vertical-flow constructed wetlands (WSVFCWs) used for secondary and tertiary treatment. The relationship between the accumulated solid material and infiltration rate, the content and particle size distribution as well as the ratio of organic and inorganic matter of the accumulated material in the filter media were determined, and the mechanisms of clogging were elucidated. The clogging mainly occurred in the upper 0-40 cm layer, and the accumulated material decreased with filter depth (along the flow direction). The main particle size contributing to clogging was ~40 μm in the WSVFCWs for secondary treatment and >110 μm in those for tertiary treatment. The accumulated material had 30-40% of organic matter. The clogging mechanisms varied as the composition of influent and aeration conditions are different in WSVFCWs. Aeration promoted the growth of biofilm and mineralization of the accumulated material as well as provided shear force in the WSVFCWs. Aeration has a good effect in extending operational time in the tertiary WSVFCW but has a mild effect in the secondary WSVFCWs because of high organic loading rate there. Both the organic and suspended solids (SS) loading rate are important factors and should be controlled to mitigate the clogging problem in WSVFCWs. [ABSTRACT FROM AUTHOR]

Sanjiang Plain is intensively used for rice production, and ditch drainage diffuse pollution prevention is crucial. Groundwater, rich in Fe ions, is the main source of irrigation water in this region. In this study, pyrite and zero-valent iron (ZVI) (sponge iron and iron scraps) were used as substrates to identify the synergistic influence of exogenous Fe 2+ addition and solid iron substrates on pollutant removal in constructed wetlands. Based on the results, iron substrates hardly improved the ammonia removal, mainly because of the physical structure and oxidation activity. At a hydraulic retention time longer than 8 h, the pollution removal efficiency in the zero-valent iron (ZVI) substrate treatment increased significantly, and the removal of nitrate (NO 3 - -N) and total phosphorus (TP) in the iron scrap substrate treatment reached about 60% and 70%, respectively. The high-throughput sequencing results showed a significant increase in the abundance of microorganisms involved in denitrification and phosphate accumulation in biofilms on ZVI substrates. The highest diversities of such microorganisms in biofilms on iron scraps were found for denitrifying bacteria ( Pseudomonas ), nitrate-reducing Fe (II)-oxidizing bacteria ( Acidovorax ), and Dechloromonas with autotrophic denitrification and phosphate accumulation, with a 43% cumulative abundance. Dechloromonas dominated in the iron sponge substrate treatment. The highest relative abundance of Acidovorax was found in the mixed iron substrate (pyrite, sponge iron, and iron scraps) treatment. The addition of ZVI substrate significantly improved the removal of NO 3 - -N and TP and reduced the hydraulic retention time through the continuous release of Fe 2+ and the promotion of microbial growth. When designing constructed wetlands for treating paddy field drainage, the appropriate addition of iron scrap substrates is recommended to enhance the pollutant removal efficiency and shock load resistance of CWs., Competing Interests: The authors declare that they have no conflicts of interest in this work., (© 2022 The Authors. Publishing Services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.)

Abstract: In order to characterize the effect of vegetation on performance of constructed wetlands (CWs) treating low and high chlorinated hydrocarbon, two pilot-scale horizontal subsurface flow (HSSF) CWs (planted with Phragmites australis and unplanted) treating sulphate rich groundwater contaminated with MCB (monochlorobenzene, as a low chlorinated hydrocarbon), (about 10mgL−1), and PCE (perchloroethylene, as a high chlorinated hydrocarbon), (about 2mgL−1), were examined. With mean MCB inflow load of 299mgm−2 d−1, the removal rate was 58 and 208mgm−2 d−1 in the unplanted and planted wetland, respectively, after 4m from the inlet. PCE was almost completely removed in both wetlands with mean inflow load of 49mgm−2 d−1. However, toxic metabolites cis-1,2-DCE (dichloroethene) and VC (vinyl chloride) accumulated in the unplanted wetland; up to 70% and 25% of PCE was dechlorinated to cis-1,2-DCE and VC after 4m from the inlet, respectively. Because of high sulphate concentration (around 850mgL−1) in the groundwater, the plant derived organic carbon caused sulphide formation (up to 15mgL−1) in the planted wetland, which impaired the MCB removal but not statistically significant. The results showed significant enhancement of vegetation on the removal of the low chlorinated hydrocarbon MCB, which is probably due to the fact that aerobic MCB degraders are benefited from the oxygen released by plant roots. Vegetation also stimulated completely dechlorination of PCE due to plant derived organic carbon, which is potentially to provide electron donor for dechlorination process. The plant derived organic carbon also stimulated dissimilatory sulphate reduction, which subsequently have negative effect on MCB removal. [Copyright &y& Elsevier]

(1) Phosphorus (P) removal has proven difficult in decentralized wastewater treatment systems, and P binding material, installed as an external filter, has been proposed for improving P removal. Especially, calcium (Ca)-rich materials have shown promising results. (2) Five calcareous materials were tested with isotherm batch experiments. The material with the highest P adsorption capacity was selected to undergo different Sol-Gel coatings, i.e., different coating dilution ratios (1:10, 1:5, and 1:1) and exposure periods (5, 10, and 15 min). The seven coated materials were evaluated by isotherm experiments. (3) The maximum adsorption capacity (Qmax) was determined by fitting the Langmuir equation. Qmax for the non-coated materials, and ranged from 0.7 (sand) to 35.1 (Catsan) mg P g−1 DW, while the coated materials ranged from 7.8 to 24.7 mg P g−1 DW depending on the coating. Based on the rotated Principal Component Analysis, the most important parameters for Qmax were the texture and the Ca content. (4) Catsan was the most promising material, but when performing a Sol-Gel coating, a trade-off between preserving Qmax and the coating thickness were evident, as the materials with the thinner coating preserved more of the sorption capacity. The development of P binding materials constitutes a useful technology in decentralized wastewater treatment systems. [ABSTRACT FROM AUTHOR]

Pig slurry is considered a high-risk effluent that causes several environmental problems if it is not adequately managed and treated. White Iberian pig farms in the southeast of Spain treat their slurry in situ using separation, double filtration, decantation, and constructed wetland treatments. However, the pretreatment process does not successfully reduce solids, which leads to clogging in the constructed wetlands (CWs). The main objective of this research paper is to reduce the turbidity and chemical oxygen demand (COD) from the effluent to make it appropriate for CW treatment. Optimization of the coagulation–flocculation (CF) process using iron chloride and a cationic flocculent DKFLOCC-1598 was investigated by a central composite design method (CCD). The effects of coagulant concentration, pH, and flocculent on the COD and turbidity removal were evaluated. The best results were found using 0.024 mol L−1 iron chloride and 0.164 mL L−1 flocculent at pH 7.5, which reduced COD by 96% and delivered turbidity removal of 97%. Therefore, the results indicate the high efficiency of the treatment method in reducing the COD and suspended solids. [ABSTRACT FROM AUTHOR]

Antibiotic resistance is a growing problem worldwide. The emergence and rapid spread of antibiotic resistance determinants have led to an increasing concern about the potential environmental and public health endangering. Wastewater treatment plants (WWTPs) play an important role in this phenomenon since antibacterial drugs introduced into wastewater can exert a selection pressure on antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Therefore, WWTPs are perceived as the main sources of antibiotics, ARB and ARG spread in various environmental components. Furthermore, technological processes used in WWTPs and its exploitation conditions may influence the effectiveness of antibiotic resistance determinants' elimination. The main aim of the present study was to compare the occurrence of selected tetracycline and sulfonamide resistance genes in raw influent and final effluent samples from two WWTPs different in terms of size and applied biological wastewater treatment processes (conventional activated sludge (AS)-based and combining a conventional AS-based method with constructed wetlands (CWs)). All 13 selected ARGs were detected in raw influent and final effluent samples from both WWTPs. Significant ARG enrichment, especially for tet(B, K, L, O) and sulIII genes, was observed in conventional WWTP. The obtained data did not show a clear trend in seasonal fluctuations in the abundance of selected resistance genes in wastewaters. [ABSTRACT FROM AUTHOR]