Influence Of Light Intensity And Wetland Substrate On Sewage Purification And Growth Of Hymenocallis Littoralis

In this paper, we mainly studied the growth and wasterwatertreatment efficiency of Hymenocallis littoralis grown in thesubminiature soil- and detritus-based wetlands under the lightintensities of 25%, 50%, 75% and 100%. The results were shown asfollows:1. 25% and 50% light intensities significantly outperformed 75%and 100% light intensities in the plant height growth of H. littoralis inthe soil-based wetlands. 50% light intensity significantly outperformed25%, 75% and 100% light intensities in the plant height in thedetritus-based wetlands. In addition, the detritus-based wetlandssignificantly outperformed the soil-based wetlands in the plant height inthe same light intensity (25%, 50%, 75%, 100%).2. There was such a relationship of light intensities of 100%＜75%＜50%＜25% in the average leaf length both the soil- and detritus-basedwetlands. The detritus-based wetlands significantly outperformed thesoil-based wetlands in the average leaf length in the same light intensity(25%, 50%, 75%, 100%).3. On the growth condition of 25%, 50%, 75% or 100% lightintensities, the root biomass of H. littoralis were minimum within rootdiameter of d≤1 mm, the next in order within 1mm＜d≤3 mm andmaximum within d＞3 mm for both the soil- and detritus-based wetlands.The root biomass among the four light intensities had no significantdifferences in the soil-based wetlands. At the same time, the rootbiomass between the soil- and detritus-based wetlands were significant(P＜0.05).4. There were no significant differences in the stem biomass of H.littoralis among the four light intensities in the soil- or detritus-basedwetlands (P＞0.05), while there were significant differences in the stem or leaf biomass of H. littoralis between the soil- and detritus-basedwetlands under 25%, 50%, 75% or 100% light intensity(P＜0.05).5. H. littoralis had no tiller grown in soil-based wetlands in 25%and 50% light intensities. The tillers were more along with theincreasing of light intensity in the detritus-based wetlands, but stoppedgrowing after October. In addition, there were also significantdifferences in the number of tillers between the soil- and detritus-basedwetlands among the four light intensities (P＜0.05).6. The detritus-based wetlands showed significantly higher removalrates than the soil-based wetlands in BOD₅, COD_cr, NH₄-N among 25%,50%, 75% and 100% light intensities, but no significant differences inSP, TN and NO₃-N removal rates. The total average removal rates of theTP were 83.51±8.33%,76.78±11.68% respectively. The detritus-basedwetlands were significantly higher than the soil-based wetlands in 100%light intensity, whereas no significant differences under 25%, 50%, 75%light intensities.7. There was such a relationship of light intensities of 100%＜75%＜50%＜25% in the removal rates of BOD5 and COD_cr, but nosignificant differences among the four light intensities in the soil-basedwetlands. 25% and 50% light intensities significantly outperformed100% light intensity in the average removal rate of TP (P＜0.05), but nosignificant differences between the other light intensities. There werelittle significant differences in the removal rates of SP, NO₃-N andNH₄-N among the four light intensities (P＞0.05). The removal rates ofthe TN were higher in the 100% light intensity than in 75% (P＜0.05), nosignificant differences between the other light intensities. In thedetritus-based wetlands, there were no significant differences among thefour light intensities in the removal rates of BOD₅, COD_cr, TP, SP, TN,NH₄-N and NO₃-N (P＞0.05).