Nitrogen distribution characteristics and pollution assessment in water along the water flow direction in a constructed wetland system treating the tailwater from wastewater treatment plants
LI Hongrui1,, HE Xu1, LIU Tao1, LIU Honglei3, XU Zhuoqi1, WEN Jiaxin1, LI Yanying3, CHEN Ziang1, MA Xiaodong1,2,, 1.School of Energy and Environmental Engineering, Hebei University of Technology, Tianjian 300401, China 2.College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China 3.Tianjin Academy of Environmental Sciences, Tianjian 300191, China
Abstract:Tianjin Lingang constructed wetland is a hybrid constructed wetland based on the tailwater of wastewater treatment plants. In order to explore the distribution characteristics and pollution status of nitrogen in water, the water samples in this wetland system were collected and analyzed. Based on the GIS Kriging interpolation method, the distribution and pollution characteristics of nitrogen species and typical physical and chemical properties of wetland water were studied; then the degree of water pollution was evaluated by single factor pollution index method. The results indicated that TN concentration in water of wetland was in the range of 0.657 to 5.576 mg·L?1, of which ${\rm{NO}}_3^ - $-N concentration was relatively high (0.095~3.920 mg·L-1) and accounted for 49.2% of TN. Along the water flow direction, the distribution of TN, ${\rm{NO}}_3^ - $-N and ${\rm{NO}}_2^ - $-N was similar, which showed a gradual decrease from the entrance to the landscape lake. The distribution of ${\rm{NH}}_4^ + $-N was relatively complicated. The highest concentration of ${\rm{NH}}_4^ + $-N occurred at the junction between landscape lake and the lower reaches of subsurface and surface flow wetlands, while the ${\rm{NH}}_4^ + $-N concentration in the surface-flow wetland was the lowest. pH and EC had relative high effect on the distribution characteristics of ${\rm{NH}}_4^ + $-N and ${\rm{NO}}_3^ - $-N. According to the single factor pollution index method, TN concentration in the wetland exceeded the standard (Pi >1), and the TN pollution was most serious in the regulation pond, which could be used as a priority control area for TN. The above results are conducive to deeply understand the occurrence and distribution characteristics of nitrogen pollutants in the hybrid constructed wetland treating the tailwater from the wastewater treatment plant. Key words:tailwater of wastewater treatment plants/ constructed wetlands/ nitrogen distribution in water of wetland/ water pollution assessment.
图1天津临港湿地采样点布设 Figure1.Layout of sampling sites in the Tianjin Lingang wetland
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Nitrogen distribution characteristics and pollution assessment in water along the water flow direction in a constructed wetland system treating the tailwater from wastewater treatment plants
1.School of Energy and Environmental Engineering, Hebei University of Technology, Tianjian 300401, China 2.College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China 3.Tianjin Academy of Environmental Sciences, Tianjian 300191, China Received Date: 2019-06-18 Accepted Date: 2019-10-24 Available Online: 2020-05-06 Keywords:tailwater of wastewater treatment plants/ constructed wetlands/ nitrogen distribution in water of wetland/ water pollution assessment Abstract:Tianjin Lingang constructed wetland is a hybrid constructed wetland based on the tailwater of wastewater treatment plants. In order to explore the distribution characteristics and pollution status of nitrogen in water, the water samples in this wetland system were collected and analyzed. Based on the GIS Kriging interpolation method, the distribution and pollution characteristics of nitrogen species and typical physical and chemical properties of wetland water were studied; then the degree of water pollution was evaluated by single factor pollution index method. The results indicated that TN concentration in water of wetland was in the range of 0.657 to 5.576 mg·L?1, of which ${\rm{NO}}_3^ - $-N concentration was relatively high (0.095~3.920 mg·L-1) and accounted for 49.2% of TN. Along the water flow direction, the distribution of TN, ${\rm{NO}}_3^ - $-N and ${\rm{NO}}_2^ - $-N was similar, which showed a gradual decrease from the entrance to the landscape lake. The distribution of ${\rm{NH}}_4^ + $-N was relatively complicated. The highest concentration of ${\rm{NH}}_4^ + $-N occurred at the junction between landscape lake and the lower reaches of subsurface and surface flow wetlands, while the ${\rm{NH}}_4^ + $-N concentration in the surface-flow wetland was the lowest. pH and EC had relative high effect on the distribution characteristics of ${\rm{NH}}_4^ + $-N and ${\rm{NO}}_3^ - $-N. According to the single factor pollution index method, TN concentration in the wetland exceeded the standard (Pi >1), and the TN pollution was most serious in the regulation pond, which could be used as a priority control area for TN. The above results are conducive to deeply understand the occurrence and distribution characteristics of nitrogen pollutants in the hybrid constructed wetland treating the tailwater from the wastewater treatment plant.
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