基于高强度农田排水的人工快速渗滤系统结构及运行管理优化研究

Optimizing structure and operation of rapid artificial filtering system for high-intensity farmland drainages

【目的】通过研究不同填料组合人工快速渗滤系统(CRI)对高排水强度、低污染浓度农田排水的净化效果,优选出适宜的填料组合及运行条件,为实际工程提供理论支持。【方法】试验设置5个污染负荷水平(即不同氮磷浓度和泥沙量),3个水力负荷水平;在每个污染负荷水平下,通过控制渗滤柱进出水量来控制不同水力负荷;并采用高通量测序分子生物学技术手段,考察系统中微生物群落结构与功能的关系,进而分析系统中不同填料组合下生物脱氮除磷效能与机制。【结果】①不同填料填装高度对各污染物的净化效果总体表现为80 cm>60 cm>40 cm;各填料组合对各污染物净化效果以粗沙、活性炭、黏土陶粒体积比为3∶2∶2、分层填装、填装高度80 cm组合(S3)最好,对总氮(TN)、总磷(TP)、氨氮(AN)、泥沙的净化率分别达到53.26%、82.51%、68.18%和78.43%。②不同污染负荷下,TN净化效果以污染负荷水平2 mg/L(W1)最好,与其他污染负荷水平呈极显著差异,其次为污染负荷水平4 mg/L(W2),净化率分别达56.70%和42.78%;AN、泥沙净化效果均以污染负荷水平W2(AN 4 mg/L、泥沙0.2 g/L)最好,净化率分别达到48.46%和81.61%,但TP净化效果各污染负荷水平间无明显差异。③随着水力负荷增大,渗滤柱对TN、TP、AN和泥沙去除率逐渐下降;在水力负荷28 L/(m^(2)·min)(T1)水平下,渗滤柱对TN、TP、AN、泥沙等各污染物的净化效果均最好,净化率分别达到48.80%、78.51%、54.88%和79.77%。④渗滤柱不同位置菌群物种数下部更多,而菌群多样性上部更高;相似填料组合其微生物群落结构具有较高的相似性;Proteobacteria(变形菌门)丰度最高,其次是Actinobacteria(放线菌门)、Firmicutes(厚壁菌门),对氮的去除起到了关键作用。【结论】人工快速渗滤系统填料填装高度80 cm,分层填装,粗沙、活性炭、黏土陶粒填料比例为3∶2∶2,适用于处理高强度农田排水,表现出较好的净化效果,对污染负荷TN为2 mg/L,AN为4 mg/L,泥沙为0.1~0.3g/L,水力负荷为28 L/(m^(2)·min)净化效果最佳,并可承受较大变幅的TP污染负荷。

【Objective】The rapid artificial filtering system(CRI)is a technology to purify drainage water from farmland.In this paper,we examine the efficiency of CRI with different filler combinations to purify drainage water characterized by high-intensity drainage rate and low pollutant concentrations.【Method】The experiments consisted of five pollutant loads represented by different nitrogen and phosphorus concentrations and sediment content,and three hydraulic loads.At each pollutant load,different hydraulic loads were implemented by adjusting the inlet and outlet water flow rates.High-throughput sequencing was used to investigate the relationship between microbial community and function of the system,as well as the mechanisms underlying the biological removal of nitrogen and phosphorus under different conditions.【Result】①The purification was the best when the filter system was 80 cm high,and the least when the filter height was 40 cm,with the height of 60 cm in between.For each filler combination,the system worked the best when the volumetric ratio of coarse sand,activated carbon and clay ceramsite was 3∶2∶2 and the filler height was 80 cm.Under these conditions,the removal rates of total nitrogen(TN),total phosphorus(TP),ammonia nitrogen(AN)and sediment were 53.26%,82.51%,68.18%and 78.43%,respectively.②The purification of TN was the best when the pollutan load was 2 mg/L(W1),followed by pollutant load of 4 mg/L(W2),with their removal rates being 56.70%and 42.78%,respectively.The purification of TP,AN and sediment were the best when AN concentration was 4 mg/L and sediment content was 0.2 g/L,with their removal rates being 48.46%and 81.61%,respectively.Pollutant load did not have a significant impact on TP purification.③With the increase in hydraulic load,the removal efficiency of TN,TP,AN and sediment decreased.The hydraulic load of 28 L/(m^(2)·min)(T1)worked the best for purifying TN,TP,AN and sediment,with their removal rates being 48.80%,78.51%,54.88%and 79.77%,respectively.④The number of bacterial species was higher in the lower part of the filtration columns,while the bacterial community was more diverse in the upper part of the columns.The microbial community was similar in columns in which the filler combinations were similar.It was found that Proteobacteria was most abundant,followed by Actinobacteria and Bacillota,all being efficient in immobilizing nitrogen.【Conclusion】Packing the media in strata to the height of 80 cm with the volumetric ratio of coarse sand,activated carbon,and clay ceramsite being 3∶2∶2 was most effective for purifying the farmland drainage water.When the pollutant load of TN,AN and sediment was 2 mg/L,4 mg/L,and 0.1 g/L to 0.3 g/L,respectively,and the hydraulic load was 28 L/(m^(2)·min),the system was most efficient for removing the pollutants.