| Water pollution is one of the major environmental problem all over the world, and eutrophication has been a serious phenomenon, become the most difficulty in environmental remediation for water pollution. With the increase of attention to the environmental ecology, using the ecological remediation methods to treat eutrophic water has become more and more popular. Becauese the ecological remediation technology is to rebuilt a healthy and self-purification ecosystem by using sun light as energy supply and higher green plants as the systems major components, not only low cost, but also environmentally and the ecologicall sound. In this paper, based on plant nutritional ecology theory and methods, and experimental technic platforms for remediating water eutrophication, the effectiveness and mechanisms were systematically studied of using aquatic macrophytes combined with bacteria to remediate eutrophic water body. The main contents include: effects of using the immobilized nitrogen cycling bacteria combined with floating macrophyte (Eichhornia crassipes ) on remediating in-site eutrophic water during the summer;Effectiveness of using the submerged macrophyte (Elodea nuttallii) combined with immobilized nitrogen cycling bacteria on in-site remediating eutrophic water in the winter-spring season. The effectiveness and mechanisms of using immobilized photosynthetic bacteria with aquatic macrophytes (Elodea nuttallii and Jussiaea stipulacea Ohwi) on treating heavy eutrophic water. The kinetics of NH4+ and NO3" was uptaken by three aquatic macrophytes. Characteristics of organic acids exudation by the three aquatic macrophytes and the crude exudates of macrophytes effects on microbe growth. The main results and conclusion are summarized as below:1. The aim of this study was to assess their influence on the nitrogen removal by combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophyte Eichhornia crassipes in summer season, and to get an insight intodifferent mechanisms involved in nitrogen removal by physical-ecological engineering technology. The results showed that floating macrophyte + bacteria (INCB) performed best effectiveness in improving water quality and decreased total nitrogen (TN) by 70.21%, nitrite and ammomium by 92.21% and 50.91%, respectively, during the experimental period. The water transparency increased from 0.5 to 1.8 m. When INCB inoculated into the floating macrophyte system, the populations of nitrosation, nitrifying, and denitrifying bacteria increased by 1 to 2 orders of magnitude compared to the un-inoculated treatments. However, the ammonifying bacteria showed no obvious difference between different treatments. And lower values of chlorophyll a, CODMn and pH in the microbial-plant integrated system were noted as compared to the Control. These results indicate that combination of floating macropht with immobilized nitrogen cycling bacteria is an effective plant-microbe system to remediate eutrophic water body in summer season.2. In order to get year-round remediation of water eutrophication, we need building the new system to maintain and improve the water quality during the winter. Using the submerged macrophye combined the INCB could achieve the goal. The results showed that the combination of submerged macrophyte and INCB performed the best effectiveness in improving the water quality, and resulted in the lowest values of TN, NO3-N, NH3, Chlorophyll a, and CODMn, whereas highest transparency by the end of the experiment among all the treatments. The reduction in TN, NO2-N, and NH4-N reached to 40.2%, 98.7%, and 85.2%, respectively, for the treatment of Elodea nuttallii + INCB. The nutrient removal from the eutrophic water body was improved more effectively by submerged macrophye in combination with the inoculated INCB. The submerged macrophyte could not only absorb nutrients from water bu also prevent nutrient transfer from the sediment to water. In addition, combination of submerged macrophy with INCB stimulated the processes of ammonification, nitrification and denitrificaton. All these may account for the better effects of plant-microbe integrated system in remediating eutrophicated water during the winter season. The effects of submerged macrophyte and immobilized bacteria on the growth of four bacteria communities: ammonifying bacteria;nitrosobacteria;nitrobacteria;denitrifying bacteria were evaluated. The results showed that combination of submerged macrophyte with INCB increased most the growth of the four communities for N cycling bacteria. Beside the ammonifying bacteria, there were 1 -3 order magnitude increase in other three kinds of bacteria and achieve significantdifference (PO.01) between the treatments and the Control. Therefore, planting submerged macrophyte combined with inoculated nitrogen cycling bacteria may be a good approach to increase N removal and accelerated the nitrogen transformation in winter season.3. This study was to determine the effectiveness of nutrient reduction in eutrophic water by aquatic macrophytes (Elodea nuttallii, Jussiaea stipulacea Ohwi), immobilized photosynthetic bacteria and the interaction of macrophytes with immobilized photosynthetic bacteria from a pilot-scale experiment, and to get an insight into different mechanisms involved in nutrient removal. Two aquatic macrophytes and immobilized photosynthetic bacteria were used to treat the artificial waste water druing 19-day batch experiment. The results illuminated that effective simultaneous removal of TN, TP, nitrate and ammonium was observed after 6 days with different treatments. After 19 days treatment, photosynthetic bacteria combined with the macrophyte of Jussiaea stipulacea Ohwi(P+F) performed better results to reduce nutrient and decrease of TN, TP, NH4-N by 98.01%, 90.26% and 98.52% respectively. The highest reduction of CODMn was achieved by photosynthetic bacteria treatment and the value was 83.13% and the reduction for TN, TP and ammonium was 57.54%, 59.65%, 62.84%, 83.13% respectively during the 19-day treating period. Greater DO in water body treated with aquatic plants or photosynthetic bacteria was found than Control. TN, TP reduction due to biomass production of Jussiaea stipulacea Ohwi accounted for 36.31% and 34.68% respectively. Beside higher biomass production, the higher nitrification and denitrification rates with the floating macrophyte than submerged macrophyte also reduced more N. Therefore, using the plant-microbe integrated systems may be a feasible remediation way to treat eutrophic water.4. Nitrogen is one of the most important nutrients causing water eutrophication, and inorganic nitrogen is the major form in water body. NH4+-N and NO3"N are the two major inorganic nitrogen forms in eutrophic water. Understanding kinetics characteristics of NH4"1" and NO3" uptake by aquatic macrophyte help to select the proper aquatic macrophyte according to the status of eutrophic water. So the experiment compared the kinetics of NR?+ and NO3". Uptake kinetics of NH4+ and NO3" by three aquatic macrophyte-Jussiaea stipulacea Ohwi, Elodea nuttallii, Eichhornia crassipes were measured. The results showed that Jussiaea stipulacea Ohwi and Eichhornia crassipes had higher values of Vmaz and Km than Elodeanuttallii, implying that the two floating macrophytes are proper for pre-treatment of the seriously polluted water. Lower values of Vmaz and Km for the submerged macrophye could be used for improving and maintaining water quality after been improved to a certain degree.5. Aquatic macrophytes can exudate organic acids, which not only can be used as organic carbon source for microbe, but also change the physical, chemical and biologic conditions of plant-microbe interface. The results showed that three aquatic macrophytes exudated similar major organic acids under no-stress condition. And oxalic acid and tartaric acid could be found in all exudation. The quantity of the two organic acids exudated varied with different aquatic macrophytes and Jussiaea stipulacea Ohwi exudated the greatest amount of oxalic and tartaric acids among all the three aquatic macrophytes. 5.7 (mgl1 h"'g"' root fresh weight) for oxalic acid and 64.48 (mgr'h'V1 root fresh weight) for tartaric acids, respectively.6. The interaction between crude exudates of aquatic macrophyte and functional bacteria play an important role to clean the eutrophic water in the plant-bacteria integrated systems. The effects of inoculated the crude extrudes of three macrophytes on growth of photosynthetic bacteria, INCB community were studied. Results showed that the crude exudates promoted the growth of photosynthetic bacteria, ammonifying bacteria and denitrifying bacteria, but inhibited the growth of nitrosation, nitrifying bacteria communities. And the different macrophyte produced different effects. The results can provid the basis theory for selecting suitabel aquatic macrophyte and functional bacteria to form effective plant-bacteria system to remediate eutrophic water body.
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