Studies On The Potential Of Constructed Wetland Candidate Plants In Cleaning Up Wastewater And Their Physiological Mechanisms

The shortage and pollution of water resources have been directly affecting industrial production, human lives, and even human health. The current disposal of wastewater is most focused on the removal of organic carbon pollutants. Therefore, the disposed water can still cause environmental problems, such as eutrophication of surface water bodies. Traditional manufacturing disposal cannot be spread out in small cities and under-developed countries because of its high cost. The hydrophyte-artificial wetland system is a new sewage technique with low cost and less energy consumption for N and P removal, and the quality of clean-up wastewater will reach the tertiary retrieval and utilization standard. Media, plants, and microbes are the essential components of artificial wetlands. Studies on the selection of artificial wetland plants and their adaptation to waterlogged conditions are becoming one of the research hot points. In this case, the ability of some candidate plants (including natural wetland plants and cultivated plants) in removing N, P nutrients from wastewater and their physiological mechanisms were investigated. The results were as follows:1. With a survey of natural marsh plants in Nanshan reservoir area, Shengzhou, Zhejiang province, four natural wetland plants such as rush (Juncus effucus L.), Sesbania cnnabina Poir., NWP1 (natural wetland plant 1) and NWP2 (natural wetland plant 2) were selected based on their vigorous growth and developed roots. And four cultivated plants such as wetland rice (Oriza sativa L.), mulberry (Morus indica L.), OP1 (ornamental plant 1), OP2 (ornamental plant 2) with their economic and ornamental value were also selected according to their adaptation to waterlogged conditions. Identifying the adaptation to wastewater conditions and the potential of removing N, P in wastewater could offer reference for enhancing the plant diversity of constructed wetlands.2. Establishment of candidate wetland plants can effectively reduce the ammonium, nitrate and phosphate concentrations in both artificial (with high nutrient concentration) and real (with lower nutrient concentration) wastewater. The removing rates of nutrients were the highest in the first 24 hours, which is due to the reduction of nutrient concentrations in the wastewater with the incubating time. Wetland rice and mulberry were most adaptive to both artificial and real wastewater, especially to the former (with high nutrient concentration),followed by OP1 和 NWP2.3. The kinetic characteristics of ammonium, nitrate and phosphate uptake by selected plants could be illustrated with Michaelis-Menten equation, and the kinetic parameters (maximum rate and Km value of absorption) could also be calculated by using the regressive equations. The maximum rates of ammonium uptake of mulberry, wetland rice and NWP1 were obviously higher than that of the other tested plants. The maximum rates of nitrate uptake of Sesbania cnnabina Poir., wetland rice and NWP1 were obviously higher than that of other tested plants. Wetland rice and rush have the highest maximum rate for phosphate uptake. The Km value of ammonium uptake of Sesbania cnnabina Poir., OP2 and NWP2 were less than that of the other tested plants. The Km value of nitrate uptake of OP1, OP2 and NWP2 were less than that of the other tested plants. Sesbania cnnabina Poir., mulberry and OP2 have the lest Km value for phosphate uptake. According to the kinetic characteristics of N and P uptake, the plants with higher maximum uptake rate could be used in first section for cleaning up wastewater with high nutrient concentration, and the plants with lower Km value could be used in second section for cleaning up wastewater with lower nutrient concentration.4. Phosphorus concentrations in plaque on root surface was significantly correlative to Fe concentrations in plaque on root surface (r=0.829**, under normal nutrition solution conditions; r=0.879**, under artificial wastewater conditions), and Fe concentrations in plaque on root surface was significantly correlative to root oxiding a...