| Ecological floating bed is a technology suitable for China’s national conditions and has a good development prospect. Implementing largescale ecological floating bed engineering should grow a large number of plants.Inevitably, it is need to consider source of plants, work amount and economic cost.This paper is based on the National Key Technology R&D Program—"Research and demonstration of urban malodorous river exogenous blocking, engineering repair and in-situ multilevel ecological purification key technology"(2009ZX07317-006). For above-mentioned, we select cold-heat-resistant plant Lythrum salicaria and Scindapsus aureus fond of half shade and wet environment, with the large water quality fluctuations and intermittent malodorous Hengdu river water in Wenzhou city as material, to study plant cultivating dynamic tests, static cultivating tests between two different degree of river pollution and field treatment experiment of continuous-flow water. Finally we put forward the new thinking of cultivation water-rooting plants in rivers directly, aim to solve the practical problems in the engineering of ecological floating bed and provide the theoretical and technical references. The main conclusions are as follows:In the plant cultivating dynamic test, the survival rate of water-rooting Scindapsus aureus and Lythrum salicaria were85%and95%, respectively. The rooting rates of survived plants were100%.All soil-rooting plants survived and took root. Compared with soil-rooting plants, the average growth rate of root of water-rooting plants was slightly faster, whereas shoot height and biomass average showed a contrary tendency. The net increment of water-rooting plants were3.0cm and5.1cm lower than that of soil-rooting plants, with the relative increment4.6and13.7percentage points, respectively. The diffirences of biomass berween the two rooting patterns were4.3g and8.1g, respectively.But the relative biomass growth rate of water-rooting plants were50.5and20.1percentage points higher than that of soilr-rooting plants, respectively. The experimental results show preliminarily that the two rooting pattern had the same growth level.The result of static lab-scale hydroponics experiment showed that there were no obvious growth differences between two rooting ways in eutrophication river water. The average growth rate of root and its relative growth amount for water-rooting plants were slightly higher than soil-rooting plants, so were increasing rate of biomass, but no obvious regularity from its relative growth rate differences. The average growth rate of water-rooting Lythrum salicaria was little lower than the soil-rooting, and the Scindapsus aureus was contrary. In summary, the root growth, shoot height and its biomass increasing were showed simliary trend for different rooting pattern, and the water-rooting plants showed stronger adaptability and were more accessible to rapid growth period.There was no significant difference of purification effect between two rooting patterns of two sets of Scindapsus aureus and Lythrum salicaria in eutrophication river water.The gap in chemical oxygen demand (CODCr) removal rate is5.3and2.4percentage points, with toatal nitrogen (TN)5.9and0.9percentage points, ammonium (NH4+-N)2.5and3.3percentage points, total phosphorus (TP)8.1and2.0percentage points, respectively. In comparison, the removal water-rooting plants had a similary treat effect with transplanted soil-rooting plant.In addition, the growth rates of two kinds of rooting plants were varied obiviously in malodorous river water condition. The relative increasing rate and average growth rate of root, shoot height and biomass of water-rooting plants were higher than soil-rooting plants. The water-rooting plant had a stronger pollutant resistant ability and could easier to live in heavily polluted river water. However, the soil-rooting plant showed different staged growth inhibition in malodorous river water.Water-rooting plants had better purification effect to malodorous river water than soil-rooting plants.The gap in chemical oxygen demand (CODCr) removal rate is11.9and13.0percentage points, with toatal nitrogen (TN)12.6and8.1percentage points, ammonium (NH4+-N)4.8and13.3percentage points, total phosphorus (TP)6.2and5.5percentage points between two sets of Scindapsus aureus and Lythrum salicaria. In contrast, water-rooting plants had more tolerance to polluted river water than soil-rooting plants.The result of field experiment with continuous influent demonstrated that it was feasible to cultivate water-rooting plants directly in ecological floating bed. The plants exhibited good adaptability and grew well in large water quality fluctuations and intermittent malodorous river water.The root length, shoot height, fresh biomass and dry biomass increased by174.4%,242.3%,485.1%and639.1%, respectively. The water-rooting Lythrum salicaria ecological floating bed had a certain effect on pollutant removal efficiencies, with20.1%～44.5%of chemical oxygen demand,13.6%～47.9% toatal nitrogen,10.2%～29.1% ammonium and19.3%～47.7% total phosphorus. Importantly, S2-and FeT were removed significantly, while the highest removal efficiency of S2-reached44.7%and the Fe2+/FeT value deceased from0.14～0.62of influent to0.16～0.41of effluent. In conclusion, the ecological floating bed could start normally and run for a long time. The plants were in good conditions, and improved the water quality of intermittent malodorous river, indicating the feasibility of the technology in engineering application. |
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