不同处理水芹浮床对城市河道黑臭污水的脱氮效果及其机理研究

Effect and mechanism of nitrogen removal in urban malodorous river using Oenanthe javanica floatingmats

通过对冬季不同留茬高度水芹(Oenanthe Javanica)浮床对城市河道污水氮循环细菌数量和脱氮效果的影响研究,试图阐明浮床植物去除污染水体氮素的可能途径.研究结果表明:不同处理水芹浮床对城市河道黑臭污水硝氮和氨氮的去除效果分别达到了52.5%～69.8%和68.1%～76.7%,19cm留茬高度水芹浮床对脱氮效果最好;19cm留茬浮床水芹根际也是各类氮循环细菌生长的最佳区域;浮床水芹处理有效地提高了系统氮循环细菌的数量,第5个换水周期试验结束时处理污水中的好氧细菌总数(A,单位为CFU.mL-1)达到最大值(7.08±0.60)×1012,其lgA增加至12.85,各类氮循环细菌比对照高1～4个数量级;同时,浮床水芹处理显著提高了氮循环细菌的群落多样性,系统内固氮菌与氨化菌、硝化菌、亚硝化菌和反硝化菌共存.研究认为,浮床水芹的吸收同化和氮循环细菌的生物脱氮是浮床水芹净化水质的两个重要途径.

Effects of floatingmats with Oenanthe javanica on the multiplication of nitrogen cycling bacteria and removal of nitrogen in the sewage of urban canal were investigated with 18 plastic tanks（size：84 cm × 64 cm × 48 cm） placed at the urban malodorous river side in Shanghai,in order to study the mechanism of floatingmats to remove nitrogen from the sewage.The results showed that removal rates of floating mats with different cress stubble heights for NO 3-N and NH 4＋-N were 52.5% ～ 69.8% and 68.1% ～ 76.7%,respectively.The floating mats with 19 cm cress stubble height showed the largest nitrogen removal effect in urban malodorous river in winter.The rhizosphere of the 19cm cress stubble height was also most suitable for the growth of nitrogen cycling bacteria.The number of total aerobic bacteria in the sewage of the water cress floating-mat system reached the highest value（7.08 ± 0.60） × 1012[lgA（CFU.mL-1） = 12.85]at the end of the 5th water change cycle and the total nitrogen cycling bacteria was 1 to 4 order of magnitudes higher than that in the control（no floatingmats）.At the same time,the presence of water cress significantly increased the community diversity of the nitrogen cycling bacteria,in which azotobacter,ammonifiers,nitrobacteria,nitrosobacteria and denitrifying bacteria were detected.Thus,we believed that both nitrogen absorption and assimilation by the plant and biodenitrification by microorganisms in the rhizosphere have played important roles during removal of nitrogen from the sewage with water cress floatingmats.