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Stormwater treatment wetlands are widely recognized as efficient and cost-effective solutions to growing stormwater problems. This study presented a new approach to evaluating the current status and trends in stormwater treatment wetlands research. The annual scientific productivity of different states was identified using a bibliometric analysis approach. The number of publications related to stormwater treatment wetlands has exhibited an increasing trend since the earliest record of publication. USA and China were among the states that had the most number of stormwater treatment wetlands-related publications and international collaborations. In terms of the population-to-publication ratio, Australia, Canada, and South Korea were found to have a higher level of scientific productivity. Analysis of frequently used keywords and terms in scientific publications revealed that the efficiency of stormwater treatment wetlands and the processes involved in the removal of nutrients and trace elements were adequately investigated; however, inquiries on the removal of organic micropollutants and emerging pollutants, such as pharmaceuticals and personal care products, microplastics, and industrial compounds, among others, are still lacking. Through the comprehensive review of related scientific works, the design, components, and primary factors affecting the performance of stormwater treatment wetlands were also identified. Future works that address the aforementioned knowledge gaps are recommended to optimize the benefits of stormwater treatment wetlands. [ABSTRACT FROM AUTHOR]

This research investigated the physical and chemical characteristics of sediment deposited at the bottom soil layer of free water surface fl ow constructed wetland (CW) treating runoff impacted stream water from an agricultural area which is important when determining the long-term maintenance requirements over the lifetime of the CW. Based on the findings, the infl uent to the CW still was polluted with high concentration of nutrients with TN and TP exceeding five and two times the water quality standard in rivers and lakes. The accumulation of sediment at the first treatment unit (sedimentation zone) of the CW augmented after the summer season signifying that the dredging of sediment must be conducted after the rainy season or until before the winter season. It was found out that the main phosphorus (P) types existing at the sediment in the CW were residual-P (R-P) and non-apatite-P (NAI-P) constituting to almost 90% of total P. While NAI-P can be released in the natural environment by increasing pH or reducing redox potential, and can be used by aquatic plants; R-P on the other hand exists with organic compounds and is diffi cult to separate. However, R-P is proportional to the absorption capacity of microorganisms which signifies that microorganisms are highly available in the CW. [ABSTRACT FROM AUTHOR]

The efficiency of nature-based facilities is mostly evaluated in terms of their pollutant removal capabilities; however, apart from water purification functions, constructed wetlands also perform ecological, cultural, and environmental education functions. A multi-criteria performance index was developed in this study to evaluate the overall efficiency of constructed wetlands. A total of 54 constructed wetlands installed across South Korea were monitored to evaluate the pollutant removal performance of the facilities. A comparison between the conventional pollutant removal-based evaluation and the developed multi-criteria index was also performed to determine the key changes in the results of evaluation when different methods are employed. Among the different types of wetlands studied, hybrid systems were found to be the most effective in terms of pollutant removal due to their complex configurations and functions. Newly constructed treatment wetlands have unstable performance and thus, a stabilization period ranging from two to five years is required to assess the facility's pollutant removal capabilities. As compared to the conventional pollutant removal-based efficiency evaluation, the comprehensive evaluation method provided a more strategic tool for identifying the facilities' strengths and weaknesses. Generally, the multi-criteria performance index developed in this inquiry can be utilized as a general tool for evaluating the sustainability of similar nature-based facilities. [ABSTRACT FROM AUTHOR]

Using total suspended solid (TSS) removal efficiency and hydraulic retention time (HRT) as design parameters a design guideline of a settling basin in a constructed wetland (CW) was suggested; as well as management of sediment and particle in the settling basin. The CW was designed to treat the piggery wastewater effluent from a wastewater treatment plant during dry days and stormwater runoff from the surrounding paved area during wet days. The first settling basin (FSB) in the CW was theoretically designed with a total storage volume (TSV) of 453 m 3 and HRT of 5.5 hr. The amount of sediment and particles settled at the FSB was high due to the sedimentation and interception of plants in the CW. Dredging of sediments was performed when the retention rate at the FSB decreased to approximately 80%. Findings showed that the mean flow rate was 21.8 m 3 /hr less than the designed flow rate of 82.8 m 3 /hr indicating that the FSB was oversize and operated with longer HRT (20.7 hr) compared to the design HRT. An empirical model to estimate the length of the settling basin in the CW was developed as a function of HRT and desired TSS removal efficiency. Using the minimum tolerable TSS removal efficiency of 30%, the length of the FSB was estimated to be 31.2 m with 11.8 hr HRT. [ABSTRACT FROM AUTHOR]

The expansion of livestock industry resulted to larger waste production and pollutant deposition in the natural environment. Advanced treatment systems for treating wastewater and discharges from livestock areas are necessary to reduce the pollutant loads in receiving water bodies. This study mainly focused on evaluating the effectiveness of a livestock constructed wetland in treating composite wastewater discharge and stormwater runoff. Water and sediment samples were collected and analyzed to determine the factors that can potentially affect the performance of the facility. Positive pollutant removal performances for turbidity (52% to 81%), TSS (61 to 82%), organics (34% to 50%), and nutrients (10% to 48%) were noted in the CW for storm events and dry days due to the continuity of flow and adequate HRT conducive to pollutant removal. SLR models for pollutant removal efficiency yielded low r2 values (0.26 to 0.53) and high errors (6.85% to 31.45%) implied that the predictive removal efficiencies were not precise. Despite the significant decrease (p <.05) in pollutant concentrations after the treatment, water quality standards were still exceeded by the effluent from the CW. Further improvements in the design of CWs can be incorporated to achieve the desired water quality standards. The findings of this inquiry can be used to establish the factors affecting the treatment performance of CWs and formulate design guidelines to improve the treatment process. • Rainfall patterns influence the performance of a constructed wetland (CW). • The CW can significantly reduce pollutant loads entering natural water bodies. • Pollutant concentrations in the CW sediments passed the soil management standards. • Design improvements are necessary to comply with the water quality standards. [ABSTRACT FROM AUTHOR]

Bacteria serve as important components of a constructed wetland (CW) system. Various bacterial communities aid in pollutant removal; however, environmental conditions and other external variables can greatly affect their performance and diversity. In this study, four constructed wetlands treating secondary livestock wastewater (LCW), agricultural runoff (ACW1 and ACW2) and urban stormwater (HCW) were investigated to evaluate the relationship between the inflow pollutants and the bacterial community. Based on the findings, the 20 dominant bacterial species in water samples collected from the livestock area (LCW) constituted 98.5% to 99.7% the total bacterial population. In the case of agricultural areas (ACW1 and ACW2), the 20 most abundant bacterial species constituted 99.7% to 99.8% of the total bacterial population. Similarly, the 20 dominant bacterial species found in the soil samples from livestock and agricultural areas made up 97.2% to 98.7% and 99.1% to 99.6% of the total bacterial population, respectively. Generally, the diversity of bacteria in soil was higher compared to water. It is important to establish a target bacterial habitat when creating CW for optimized ecological functions. • Proteobacteria was the most dominant species found in the soil and water samples. • Considering bacterial habitat, soil is more stable compared to water. • Target bacterial habitat should be considered in designing constructed wetlands. [ABSTRACT FROM AUTHOR]

The nitrogen changes and the nitrogen mass balance in a free water surface flow constructed wetland (CW) using the four-year monitoring data from 2008 to 2012 were estimated. The CW was composed of six cells in series that include the first settling basin (Cell 1), aeration pond (Cell 2), deep marsh (Cell 3), shallow marsh (Cell 4), deep marsh (Cell 5) and final settling basin (Cell 6). Analysis revealed that the NH + 4 -N concentration decreased because of ammonification which was then followed by nitrification. The NO − 2 -N and NO − 2 -N were also further reduced by means of microbial activities and plant uptake during photosynthesis. The average nitrogen concentration at the influent was 37,819 kg/year and approximately 45% of that amount exited the CW in the effluent. The denitrification amounted to 34% of the net nitrogen input, whereas the accretion of sediment was only 7%. The biomass uptake of plants was able to retain only 1% of total nitrogen load. In order to improve the nutrient removal by plant uptake, plant coverage in four cells (i.e., Cells 1, 3, 4 and 5) could be increased. [ABSTRACT FROM AUTHOR]