| Wastewater from the livestock and poultry breeding is one of the main causes of non-point pollution in Chinese countryside. The wastewater pollution contained high concentrations of organic matters, ammonia nitrogen and suspended substances is long-term and irreversible. Although the primary and secondary treatments can remove a large amount of organic matters, ammonia nitrogen and suspended substances, the national standard Gradeâ…¡andâ…¢for the environmental quality standards of surface water (GB3838-2002) can be achieved only after the succeeding treatments. The constructed wetland is the best one among the succeeding treatments. In this work, stain resistance and decontamination effect of wetland plants in constructed wetland for wastewater treatment, as well as their growth conditions in the wastewater were investigated based on the plant selection principle in constructed wetland and the theory of ecosystem function. The wetland plant species, which are suitable for growing in wetland under the conditions of sub-tropical monsoon, were selected. Moreover, the selected plant species were applied to treat the wastewater from livestock and poultry breeding, and the selectivity and purification effect of the plant species for this kind of wastewater were examined.The wetland plant resources in Ya'an was extensively investigated. Nine plant species, Cannaceae indica var. flava, Iris pseudoacorus, Triglochin palustre and those have never been reported in constructed wetland system such as R. sieboldii Miq., Cardamine hirsuta Linn., Delphinium anthriscifolium Hance, Valeriana offeinalis L, Caprifoliaceae Sambucus chinensis, and Ranunculus sceleratus Linn, were selected as the wetland plants. Different substrates, such as the purplish soil, the river sand and the gravel were selected to simulate a constructed wetland system in indoor condition. The test results are listed as follow.(1) The constructed wetland systems with the wetland plants had better purification effect for the wastewater from livestock and poultry breeding than that without the wetland plants. The wetlands cultivated by different plant species had different purification effect for the wastewater. The amount of CODcr, TN, TP and NH4+-N removed by the different plant wetland systems increased with the processing time extending. The growth tendency of the plant species had a positive correlation with the removal of the contaminants. Under the conditions that the hydraulic detention time is 5d, the removal rate of CODCr, TN, TP, NH4+-N and turbidity in the wastewater arrived at stable conditions and showed a better effect.(2) The selected nine plants, Cannaceae indica var. flava, Iris pseudoacorus, Triglochin palustre, R. sieboldii Miq., Cardamine hirsuta Linn., Delphinium anthriscifolium Hance, Valeriana offeinalis L., Caprifoliaceae Sambucus chinensis and Ranunculus sceleratus Linn., had a certain Processing capacity. Among the plants, the purification effect of six plants, R. sieboldii Miq., Cardamine hirsuta Linn., Delphinium anthriscifolium Hance, Valeriana offeinalis L., Caprifoliaceae Sambucus chinensis and Ranunculus sceleratus Linn., were better than others. After treatment, the water quality reached the classâ…¡andâ…¢of 'the environmental quality standards of surface water (GB3838-2002).(3) The phosphorus removal was mainly based on the absorption of the substrates. Althongh the absorption capacity of the soil was higher than that of the river sand and the gravel had the lowest capacity, different substrates had no significant difference.(4) The concentration of nitrogen and phosphorus increased in the overground and underground parts of plants in the simulated constructed wetland system, and that also raised to some extent in the substrates. The cumulative amount of nitrogen and phosphorus in the overground parts of the plants were obviously higher than that in the underground parts. After the experiments, the amount of phosphorus had a significant increase in the substrates. This results are in accordance to the theory that the physical and chemical reactions of the substrates are the main approaches to remove phosphorus in the constructed wetland.(5) The nitrogen concentration in each plant organs in constructed wetland was higher than control group. For Cardamine hirsuta Linn., Delphinium anthriscifolium Hance, R. sieboldii Miq., Valeriana offeinalis L., Triglochin palustre and Caprifoliaceae Sambucus chinensis, the nitrogen concentration distribution in the plant organs was leaves> roots> stalk before the experiments, while which was leaves> stalk>roots after the experiments. The order of the organic nitrogen absorbed in the plant organs was stalk> leaves> roots during the experimental period. For Ranunculus sceleratus Linn., Iris pseudoacorus and Cannaceae indica var. flava, the nitrogen concentration distribution in the plant organs was leaves> stalk> roots before the experiments, while which was leaves> roots> stalk after the experiments. The order of the organic nitrogen absorbed in the plant organs was roots > leaves> stalk during the experimental period.(6) The phosphorous concentration in each plant organs in constructed wetland was higher than control group. The concentration distribution in each plant organs was roots> leaves> stalk before the experiments, while which was leaves>roots> stalk after the experiments. The order of the organic phosphorus absorbed in the plant organs was leaves > stalk> roots during the experimental period.(7) After the nine plants growing three months in the constructed wetland, the total biomass of each plants were among 0.4521-0.7072 kg per bucket. Cannaceae indica var. flava was the highest among the nine plants regardless of ground and underground biomass, which total biomass reached 0.7072 kg per bucket, but its ratio of A/U was only 0.8228. Next is Ranunculus sceleratus Linn.that total biomass reached 0.7047 kg per bucket, and its ratio of A/U is also secondary than that of Cannaceae indica var. flava.
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