Application of a constructed wetland system for polluted stream remediation

• Published in: Journal of hydrology (Amsterdam) Vol. 510; pp. 70 - 78
• Main Authors: Tu, Y.T., Chiang, P.C., Yang, J., Chen, S.H., Kao, C.M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 14.03.2014; Elsevier
• Subjects: Alcaligenes; Bacillus pumilus; Bacteria; Constructed wetland; Construction; Earth sciences; Earth, ocean, space; Ecosystem; Engineering and environment geology. Geothermics; Exact sciences and technology; Hydrology; Hydrology. Hydrogeology; Microorganisms; Nitrification; Nitrosospira; Nitrosovibrio; Phosphorus; Pollution, environment geology; Pseudomonas; River water purification; Sediment; Sediments; Stenotrophomonas maltophilia; Streams; Water quality; Water resources; Wetlands; Far East; Asia; Taiwan; Taiwan, Kaohsiung; Taiwan, Kaoping R; River water purification; Sediment; Constructed wetland; Ecosystem; Water quality; metals; nitrites; nitrates; pollution; denitrification; nutrients; remediation; wetlands; hydraulics; oxygen; flow; retention; phosphorus; rivers; nitrogen; streams; concentration; water quality; ecosystems; water resource management; drainage; strategy
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2013.12.015

•A wetland was constructed to restore stream water quality and rehabilitate the ecosystem.•The multi-function wetland could remove organics, coliforms, and nutrients effectively.•The wetland system caused the variations in the microbial diversities and dominant bacteria.•The molecular biology techniques provide a guide for wetland microbial ecology evaluation.•The constructed wetland can be developed into a river water quality improvement alternative. In 2010, the multi-function Kaoping River Rail Bridge Constructed Wetland (KRRBW) was constructed to improve the stream water quality and rehabilitate the ecosystem of the surrounding environment of Dashu Region, Kaohsiung, Taiwan. The KRRBW consists of five wetland basins with a total water surface area of 15ha, a total hydraulic retention time (HRT) of 10.1days at a averaged flow rate of 14740m3/day, and an averaged water depth of 1.1m. The influent of KRRBW coming from the local drainage systems containing untreated domestic, agricultural, and industrial wastewaters. Based on the quarterly investigation results of water samples taken in 2011–2012, the overall removal efficiencies were 91% for biochemical oxygen demand (BOD), 75% for total nitrogen (TN), 96% for total phosphorus (TP), and 99% for total coliforms (TC). The calculated first-order decay rates for BOD, TN, TP, NH3–N, and TC ranged from 0.14 (TN) to 0.42 (TC) 1/day. This indicates that the KRRBW was able to remove organics, TC, and nutrients effectively. The high ammonia/nitrate removal efficiency indicates that nitrification and denitrification processes occurred simultaneously in the wetland system, and the detected nitrite concentration confirmed the occurrence of denitrification/nitrification. Results from sediment analyses reveal that the sediment contained high concentrations of organics (sediment oxygen demand=1.9–5.2gO2/m2day), nutrients (up to 15.8g total nitrogen/kg of sediment and 1.48g total phosphorus/kg of sediment), and metals (up to 547mg/kg of Zn and 97mg/kg of Cu). Appropriate wetland management strategies need to be developed to prevent the release of contaminants into the wetland system. The wetland system caused the variations in the microbial diversities and dominant microbial bacteria. Results show the dominant nitrogen utilization bacteria including Denitratisoma oestradiolicum, Nitrosospira sp., Nitrosovibrio sp., D. oestradiolicum, Alcaligenes sp., Steroidobacter denitrificans, Hydrocarboniphaga effuse were responsible for nitrogen removal, and the dominant carbon degrading bacteria (Stenotrophomonas maltophilia, H. effuse, Alcaligenes sp., Pseudomonas sp., Fusibacter sp., Chlofoflexi, Guggenheimella bovis, Bacillus pumilus) were responsible for carbon reduction. The denaturing gradient gel electrophoresis (DGGE) and nucleotide sequence techniques provide a guide for microbial ecology evaluation, which can be used as an indication of contaminants removal. Results from this study show that constructed wetlands have the potential to be developed into an environmentally acceptable river water quality improvement and wastewater polishment alternative for practical application.