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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 453m(3) and HRT of 5.5hr. 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 21.8m(3)/hr less than the designed flow rate of 82.8m(3)/hr indicating that the FSB was oversize and operated with longer HRT (20.7hr) 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 31.2m with 11.8hr HRT., (Copyright © 2014. Published by Elsevier B.V.)

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., (Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.)

Constructed wetland (CW) is the preferred means of controlling water quality because of its natural treatment mechanisms and function as a secondary or tertiary treatment unit. CW is increasingly applied in Korea for secondary effluent of livestock wastewater treatment. This study was conducted to recognize the characteristics of contaminants in the accumulated sediment at the bottom soil layer and to reduce the phosphorus release from sediments of the free water surface CW for the treatment of secondary piggery wastewater effluent from a livestock wastewater treatment facility. The results revealed that the dominant phosphorus existence types at near the inlet of the CW were non-apatite phosphorus (59%) and residual phosphorus (32%) suggesting that most of the particles of the influent are made up of inorganic materials and dead cells. Sediment accumulation is important when determining the long-term maintenance requirements over the lifetime of CW. Continuous monitoring will be performed for a further assessment of the CW system and design.

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

This study assessed the factors affecting the growth and survival of microorganisms in a small horizontal subsurface flow constructed wetland (HSSF CW) treating stormwater runoff from highly impervious road and parking lot through long-term monitoring from 2010 until present. The HSSF CW facility consisted of sedimentation or pre-treatment zone, vegetation zone, and effluent zone, and employed filter media including bio-ceramics, sand, gravel, and wood chips. Results showed that flow reduction in the wetland through filtration and sedimentation played an important part in the overall performance of the HSSF CW. In addition, vegetation growth was found to be affected by pollutant and stormwater inflow in the HSSF CW. Vegetation near the outflow port exhibited greater growth rates by about 6.5% to 64.2% compared to the vegetation near the inflow port due to the less stormwater pollutant concentrations via filtration mechanism in the plant or media zone of the HSSF CW. The pollutant inflow from road and parking lot played an important role in providing good environment for microbial growth especially for the dominant microbial phyla including Proteobacteria, Actinobacteria and Acidobacteria in the HSSF CW. The findings of this research are useful in understanding treatment mechanisms and identifying appropriate design considerations for HSSF CW. [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]