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近年来,关于污水厂尾水处理的研究逐渐受到关注。污水在经过二级生化处理后,虽然污染物能够得到绝大部分的去除,但出水中污染物的浓度仍然远超地表水环境质量标准,直接排放仍会对地表水环境造成一定程度的污染。人工湿地技术由于出水水质稳定,对氮、磷有较高的去除率,管理方便且运行费用小等诸多优势逐渐成为处理污水厂尾水的主要技术之一[1-2]。然而,传统的人工湿地系统在实际应用中存在一些弊端。近年来,对传统人工湿地系统的改良研究逐渐兴起,且在基质改良、微生物强化等方面取得了较大进展[3-4]。在实际运行中,湿地水力负荷的大小严重影响污染物的去除效率,目前关于改良型人工湿地在水力负荷方面的研究较少,对不同的改良型人工湿地系统之间受水力负荷影响的对比研究更是缺乏。以往水力负荷对传统人工湿地去除效率影响的研究成果,对改良型人工湿地应用的适用性尚未得到验证。
水力负荷是影响人工湿地处理效率的重要参数。水力负荷直接影响水力停留时间,进而影响污染物的去除率,包括氨氮(
$ {\rm{NH}}_4^{\rm{ + }}$ -N),硝酸盐($ {\rm{NO}}_3^{\rm{ - }}$ )和耗氧有机物(以COD计)等污染物[5]。有研究[6-7]表明,人工湿地对污染物的去除率会随着水力负荷的增大而降低,然而较低的水力负荷又意味着较低的处理量或较大的湿地处理面积,且不同类型的湿地系统之间受水力负荷的影响程度不同[8-9]。因此,研究不同的改良型人工湿地受水力负荷的影响趋势以及确定湿地运行的最佳水力负荷尤为重要。有研究[10]表明,生物炭和活性炭拥有丰富的孔隙结构,因其巨大的比表面积以及较强的吸附能力,故其表面能够吸附大量的污染物,已被证明是提高污染物去除率的有效材料。而湿地的反硝化能力不足是制约系统脱氮的重要因素。本研究分别使用生物炭、活性炭以及厌氧-异养反硝化菌对人工湿地进行了改良,采用对比实验,搭建了3套规模相同的垂直流人工湿地:1号为生物炭+活性炭改良基质系统;2号为厌氧-异养反硝化菌强化微生物系统;3号为生物炭+活性炭+反硝化菌强化微生物系统。通过改变水力负荷的大小探究了3套垂直流人工湿地系统对模拟污水厂尾水处理效果的影响,确定了3套系统运行的最佳水力负荷,以期为改良型垂直流人工湿地对污水厂尾水的深度处理提供参考。
水力负荷对改良型垂直流人工湿地降解模拟污水厂尾水效果的影响
Effect of hydraulic loading on the degradation of the simulated tail water from wastewater treatment plant by improved vertical flow constructed wetland
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摘要: 为确定改良型垂直流人工湿地降解模拟污水厂尾水的最佳水力负荷,采用生物炭和活性炭改良、微生物强化以及同时添加生物炭、活性炭和微生物改良强化的3套垂直流人工湿地系统,研究了其在3种水力负荷条件下(0.25、0.5和1 m3·(m2·d)−1),对模拟污水厂尾水中污染物的去除效果。结果表明,3套垂直流人工湿地系统均在低水力负荷(0.25 m3·(m2·d)−1)时对模拟污水厂尾水中
$ {{\rm{NH}}_4^ + }$ -N、TN、TP和COD的去除率较高,但随着水力负荷的增大其去除率逐渐降低。3套垂直流人工湿地系统对$ {{\rm{NO}}_3^{\rm{ - }}}$ -N的去除率均在高水力负荷(1 m3·(m2·d)−1)时较高,且随着水力负荷的变大,其去除率逐渐升高,但去除率的增长幅度变缓;实验证明,生物炭和活性炭改良基质能够提高湿地系统对$ { {\rm{NH}}_4^ + }$ -N、TN、TP和COD的去除效果,并且在低水力负荷时对$ {{\rm{NH}}_4^ +} $ -N、TN和COD的去除拥有更好的改良效果,而对TP去除的改良则在高水力负荷时优于在低水力负荷时。厌氧-异养反硝化菌能够提高湿地系统对$ {{\rm{NH}}_4^ + }$ -N、$ {{\rm{NO}}_3^{\rm{ - }}}$ -N和TN的去除效果,并且在高水力负荷时对$ { {\rm{NO}}_3^{\rm{ - }}}$ -N的改良效果优于低水力负荷,而在低水力负荷时对$ { {\rm{NH}}_4^ +} $ -N和TN具有更好的改良效果。综合考虑多种污染物的去除效果,确定3套改良型垂直流人工湿地系统的最佳水力负荷为0.5 m3·(m2·d)−1。-
关键词:
- 改良型垂直流人工湿地 /
- 水力负荷 /
- 生物炭 /
- 异养反硝化菌
Abstract: To study the optimal hydraulic loading of improved vertical flow constructed wetland (VFCW) degrading the simulated tail water in wastewater treatment plant, three improved VFCW systems were built with addition of biochar-activated carbon, microorganisms or biochar-activated carbon-microorganisms, respectively. The effects of different hydraulic loading conditions (0.25, 0.5 and 1 m3·(m2·d)−1) on the pollutants removal from the simulated tail water in wastewater treatment plant were investigated. Results showed that the three improved VFCW systems had high removal rates of$ {\rm{NH}}_4^ + $ -N, TN, TP, and COD in the tail water of simulated sewage plant at a low hydraulic loading of 0.25 m3·(m2·d)−1, and the removal rates progressively decreased with the increase of hydraulic loading. The removal rate of$ {\rm{NO}}_3^{\rm{ - }}$ -N by these three improved VFCW systems was higher at the hydraulic loading of 1 m3·(m2·d)−1, and the removal rate increased with the increase of the hydraulic loading, while the increment of removal rate slowed down gradually. The experiment results showed that biochar-activated carbon modification could improve the removal efficiencies of$ {\rm{NH}}_4^ + $ -N, TN, TP and COD in VFCW systems, even had a better removal effects for$ {\rm{NH}}_4^ + $ -N, TN and COD at low hydraulic loadings, while higher TP removal occurred at higher hydraulic loadings. The presence of anaerobic-heterotrophic denitrifying bacteria could improve the removal effect of$ {\rm{NH}}_4^ + $ -N,$ {\rm{NO}}_3^{\rm{ - }}$ -N and TN in VFCW system, and better improvements were achieved for$ {\rm{NO}}_3^{\rm{ - }}$ -N removal occurred at higher hydraulic loadings, while for$ {\rm{NH}}_4^ + $ -N and TN removal at lower hydraulic loadings. Comprehensive consideration of the simultaneous removal of various pollutants, 0.5 m3·(m2·d)−1 was recommended as the optimal hydraulic loading for the three improved VFCW systems. -
表 1 模拟污水厂尾水中各污染物的浓度
Table 1. Concentration of pollutants in simulated tail water
mg·L−1 检测结果 浓度范围 平均值 COD 40.07~54.67 47.94±3.95 $ {\rm{NH}}_4^{\rm{ + }}$ -N5.64~10.30 7.46±1.29 $ {\rm{NO}}_3^{\rm{ - }}$ -N2.15~5.84 4.13±0.89 TN 8.2~16.83 12.77±3.94 TP 0.37~0.89 0.61±0.14 -
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