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| Characteristics of phosphorus fate in constructed wetlands with different plant combinations |
| Received:July 07, 2020 |
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| KeyWord:agricultural non-point source pollution;constructed wetlands;plant combinations;emergent aquatic plant;floating plants |
| Author Name | Affiliation | E-mail | | YE Lei | School of Water Resources and Civil Engineering, Hunan Agricultural University, Changsha 410128, China
Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | LI Xi | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | TIAN Ri-chang | Zhongshan Bureau of Ecology and Environment, Zhongshan 528403, China | | | WU Feng-ping | School of Water Resources and Civil Engineering, Hunan Agricultural University, Changsha 410128, China | | | MENG Cen | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | XIA Meng-hua | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | GUO Ning-ning | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
School of Resources and Environmental Science, Hunan Normal University, Changsha 410006, China | | | FAN Xiang | School of Water Resources and Civil Engineering, Hunan Agricultural University, Changsha 410128, China
Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | LI Yu-yuan | Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | WANG Hui | School of Water Resources and Civil Engineering, Hunan Agricultural University, Changsha 410128, China | wanghuisb@126.com |
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| Abstract: |
| Constructed wetland(CW) technology is an important method of agricultural non-point source pollution treatment, and phosphorus removal is the main source of difficulty in sewage treatment. This study used a subtropical hilly region as the research area and combined rural farming wastewater, domestic sewage, and farmland drainage to form compound sewage as the treatment object. Through field experiments, wetlands were constructed with floating water plants(Myriophyllum elatinoides)alone or M. elatinoides in combination with different emergent aquatic plants(Iris pseudacorus, Canna glauca, or Pontederia cordata), to explore the influence of different plant combinations on the effectiveness of phosphorus treatment and removal in the CWs. The results from March to September showed that the plant combination wetland had a significant effect on phosphorus in rural sewage, and this effect was mainly seen in the removal of inorganic phosphorus. Total phosphorus concentration in wetland inlet water ranged from 2.16~5.93 mg·L-1, and the outlet water concentration ranged from 0.34~0.48 mg·L-1 among the different plant combinations; these values were lower than urban sewage discharge standard Grade A(0.5 mg·L-1). The phosphorus removal effect was greatest in the M. elatinoides + P. cordata wetland. Total phosphorus load of the CWs varied from 45.50~47.13 g·m-2·a-1 among the different plant combinations, and the wetland composed of M. elatinoides + P. cordata had a total phosphorus load of 47.13 g·m-2·a-1, which was significantly higher than the 39.62 g·m-2·a-1 value measured in the control wetland. Sediment adsorption and precipitation were the main phosphorus removal mechanisms in the CWs, accounting for 72.44%~75.62% of total phosphorus removal. Total phosphorus accumulation of aquatic plants ranged from 9.65~12.51 g·m-2·a-1, and this accounted for 21.00%~26.54% of total phosphorus removal. In the experiment, compared to the M. elatinoides wetland, the proportion of total phosphorus removed from plant combination CWs through sediment adsorption decreased by 1.71%~4.89%, and phosphorus adsorption by plants increased by 0.97%~6.28%. Compared to the control wetland, the proportion of total phosphorus removed decreased by 18.11%~21.29%. Utilizing plant combinations in CWs can delay the adsorption saturation time of the sediment and increase the phosphorus absorption rate of plants. |
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