| As an effective in-situ water remediation technology, Ecological Floating Bed System(EFBS) possessed many advantages:(1) remove pollutants directly from water body; (2) be able to dispense with land; (3) low operating cost and convenient maintenance management. So EFBS technology have aroused wide concern. Current research showed many kinds of EFBS with good decontamination performance had been developed and applied in the ecological remediation of lentic (lake, reservoir, etc.) and lotic (river) polluted water. But it is still not clear that what concentration range these EFBS could work effectively? Which kind EFBS was best for certain kind of contaminant? And there was rare report on systematic comparison of decontamination efficiency of different EFBS.Therefore, different process EFBS was studied in our paper. Firstly, the decontamination efficiency of traditional EFBS to different concentration of pollutant was studied, and then, Combined Ecological Floating Bed System (CEFBS) and Movable Wetland Floating Bed System (MWFBS) was designed and constructed. their decontamination efficiency was evaluated and compared. Finally, the decontamination mechanism was discussed through Phytoaccumulation, radial oxygen loss (ROL) and microorganism. Our results were as follows:1,The decontamination efficiency of traditional EFBSOn the basis of ecologicl principle and low cost,6 kinds of wetland plants (Canna generalis, Cyperus alternifolius, Acorus calamus, vetiveria zizanioides, Thalia dealbata and Pennisetum purpureum) were chose to constructed the EFBS in order to study the decontamination performance in different concentration sewage. For one EFBS, only one kind of plant was planted. Results showed that:All the 6 wetland plants could maintain their regularly growth in high concentration of N,P and organic matter. They all had high remove loading to CODCr,TP,TN and NH4+-N. A good decontamination performance to CODcr was obtained for all EFBS (p>0.05); The EFBS with T. dealbata, C. generalis, C. alternifolius and A. calamus all had a higher remove loading than the EFBS with P. purpureum and V. zizanioides (p<0.05); EFBS with C. generalis, A. calamus and T. dealbata showed the best decontamination performance to TN and NH4+-N (p<0.05).2. The decontamination efficiency of CEFBSFour kinds of CEFBS were constructed by the pairwise combination of two kinds of plants (C. generalis and C. alternifolius) and two kinds of paddings (elastic packing and combination packing). Compared with the EFBS with each paddings only, to study the decontamination performance in different concentration sewage. Results showed that:All the 6 EFBS had good decontamination performance to CODCr, and there was no significant difference among them (p>0.05), which showed that plant and microorganism worked simultaneously in the degrdation of CODCr. And microorganism played a more important role;All the 6 EFBS had good decontamination performance to TP in different concentration sewage, and the EFBS with plant showed notably high decontamination effiency compared to the EFBS with paddings only (p<0.05), which showed that the remove for EFBS to P was depend on the cooperation of plant and microorganism, and plant play a more important role;The 6 EFBS also had good decontamination performance to TN and NH4+-N, which showed the same trend as TP:The EFBS with plant showed notably high decontamination effiency compared to the EFBS with paddings only (p<0.05),3,The decontamination efficiency of MEFBSOne year sampling and monitoring work were conducted to study the MEFBS in the river channal of inland river in the Pearl River Delta. Results showed that:The MEFBS with C. generalis, C. alternifolius, A. calamus, T. dealbata and P. purpureum could worked regularly in the polluted water, the survival rate of plant reached up to 95% and a high growth rate was maintained for the whole year. High remove loading to CODcr was maintained since the MEFBS worked, and a notably decrease to CODCr was obtained in the demonstration plot compared to the check plot (p<0.05). This showed that the microorganism in both the plant and paddings played a crucial role; During the EFBS working period, the remove loading to TP, TN and NH4+-N was high in check plot, showed a significant difference compared to demonstration plot. This also showed that besides the absorption of plant, the microorganism in paddings also played a important role. 4,The performance comparison of different EFBSThe decontamination performance were compared among different EFBS, results showed that:All the three EFBS showed good decontamination performance to CODcr, of which the decontamination performance of CEFBS and MEFBS were better than EFBS(p< 0.05); To remove TP, TN and NH4+-N, the decontamination performance of EFBS with plant were notably higher than EFBS with paddings only (p<0.01).5,The decontamination mechanism of EFBSThere was a significantly positive correlation between the ROL and TN removing load of the two kinds of floating bed plant (C. generalis, C. alternifolius) (p<0.01) and there was also a positive correlation between ROL and NH4+-N (p<0.05). The plant porosity was positively correlated to the removing load of NH4+-N and CODcr (p<0.05).The abundance of ammonifying bacteria, nitrifying bacteria and nitrosification bacteria played a important role for the contaminant remove which was proved by their correlation. The abundance of ammonifying bacteria and nitrifying bacteria had a positive correlation (p< 0.05) and a significantly positive correlation (p<0.01) to the removing load of TN and NH4+-N respectively. The abundance of nitrifying bacteria had a significantly positive correlation to the removing load of CODCr (p<0.05); There was a significant correlation between the abundance of nitrosification bacteria and the removing load of TN (p<0.01), and there was also a correlation to the removing load of NH4+-N and CODCr(p<0.05).In sum, the CEFBS showed the best decontamination performance among the three kinds of EFBS, followed by MEFBS and traditional EFBS.
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