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| The application of hybrid constructed wetlands in rural sewage treatment and the removal effect on PPCPs |
| Received:January 16, 2025 |
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| KeyWord:rural domestic sewage;hybrid constructed wetlands;ecological treatment;conventional pollutants;pharmaceuticals and personal care products(PPCPs) |
| Author Name | Affiliation | E-mail | | HU Yujia | College of Environmental and Engineering, Guilin University of Technology, Guilin 541006, China | | | HU Zeyu | College of Environmental and Engineering, Guilin University of Technology, Guilin 541006, China | | | MO Hu | Hengsheng Water Environment Treatment Co., Ltd., Guilin 541004, China | | | MENG Zhensi | Hengsheng Water Environment Treatment Co., Ltd., Guilin 541004, China | | | ZHANG Yanan | Guangxi Key Laboratory of Theory and Technology for Environmental Pollution Control, Guilin University of Technology, Guilin 541006, China | | | BAI Shaoyuan | Collaborative Innovation Center for Water Pollution Control and Water Safety in Karst Area, Guilin University of Technology, Guilin 541006, China | baisy@glut.edu.cn |
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| Abstract: |
| In order to explore the treatment of rural domestic sewage by constructed wetlands, this study takes the "vertical flow+two-stage horizontal subsurface flow" hybrid constructed wetlands rural domestic sewage treatment project that has been in operation for many years as the object, monitors the changes in influent and effluent water quality in typical years during operation, and the contribution of each wetland unit to pollutant removal. At the same time, the existence and removal of typical new pollutants pharmaceuticals and personal care products（PPCPs）in the project were investigated. The results indicated that due to the relatively small rural population, the quality of sewage was greatly affected by the operating conditions of restaurants in the village, especially organic matter. After the restaurant closed, the chemical oxygen demand（COD）concentration in the influent water decreased by nearly 60%. During operation, the constructed wetlands had good resistance to shock lOads, with average effluent COD, ammonia nitrogen（NH+4-N）, and total phosphorus（TP） concentrations of 41.27, 13.67 mg·L-1, and 2.95 mg·L-1, respectively. Organic matter was mainly removed through microbial decomposition and plant absorption. In the vertical flow wetland, the water flow had more sufficient contact with the substrate, microorganisms, and plant roots. Moreover, it was in a semi-saturated state, with high microbial diversity and good oxygen transfer, which was conducive to microbial decomposition. Therefore, it had the highest contribution rate to the removal of COD, reaching 62.90%. The removal of TP was mainly the result of the adsorption effect of the substrate. The removal contribution rate of the first-level horizontal flow wetland was 59.13%, and it performed the best among the three groups of wetlands. TN and NH+4-N were gradually removed in wetlands at all levels through reactions such as ammonification, nitrification, and denitrification. In addition, a total of 19 types of PPCPs were detected in the influent water. The constructed wetland had a remarkable removal effect on PPCPs, and its degradation mechanism involved various pathways such as plant absorption and metabolism, microbial decomposition, substrate adsorption, and photolysis. The study found that the removal efficiency of PPCPs was negatively correlated with their distribution coefficient（Kd）in the substrate. PPCPs with lower Kd values were more easily removed through mechanisms such as plant absorption, microbial degradation, and photolysis in constructed wetlands due to their higher solubility and bioavailability. The study showed that hybrid constructed wetlands had strong resistance to shock lOads and performed well in removing conventional pollutants and PPCPs. |
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