以城市污水为水源和肥源对荒漠化土壤的修复效果

为了同步实现城市污水净化和荒漠化土壤修复,以荒漠化土壤(沙土)作为人工湿地基质(基质深度分别为0.1和0.6 m),分析不同运行条件(植物种类、水力负荷、基质深度、季节变化等)下湿地对净化城市污水、修复荒漠化土壤的效果. 结果表明:经过2 a的修复,城市污水中污染物作为荒漠化修复的肥源可以快速富集到荒漠化土壤中. 与原沙相比,沙土中w(有机质)、w(TN)、w(碱解氮)、w(TP)、w(速效磷)及电导率均极显著增加(P<0.01),而pH并无显著变化(P>0.05). 沙土容重极显著降低(P<0.01),孔隙率极显著增大(P<0.01). 当城市污水作为荒漠化土壤修复水源时,即使水力负荷低至0.0075 m3/(m2·d),植物仍能正常生长. 基质深度为0.1 m的潜流湿地在不同水力负荷时对污水中COD_Cr、TN、TP的最低平均去除率分别为59.46%、77.45%、62.36%；基质深度为0.6 m的潜流湿地对污水中三者的平均去除率分别为59.24%、32.02%、57.89%；基质深度为0.6 m的表面流湿地对污水中三者的平均去除率则分别为80.40%、14.00%、29.31%. 研究显示,以城市污水为水源和肥源对荒漠化土壤修复2 a后,沙土中养分含量均显著增加,沙土结构也得到明显改善,各湿地在夏秋季对污水中COD_Cr、TN、TP均有较好的去除效果. 

Restoration of Desertification Soil Using Municipal Wastewater as Water and Fertilizer Source

Constructed wetlands with desertification soil (sandy soil) substrate were used to simultaneously treat municipal wastewater and remediate desertification soil. The depths of the substrate were 0.1 and 0.6 m. The effects of constructed wetlands running under different conditions including different kinds of plants, hydraulic loading, depth of substrate and seasonal changes for treating municipal wastewater and remediating the desertification soil were studied. The results showed that pollutants in the municipal wastewater (i.e., the fertilizer source of desertification restoration) could be quickly enriched in the desertification soil after two years' restoration. Compared to the original sand, soil organic matter, total nitrogen, available nitrogen, total phosphorus, available phosphorus content and electrical conductivity increased significantly (P<0.01), while pH change was not significant (P>0.05). In addition, significant decreases of bulk density (P<0.01) and significant increasing porosity of soil (P<0.01) were found. When the municipal wastewater was used as the water source of desertification restoration, even with the hydraulic loading low at 0.0075 m3/(m2·d), cultivated plants could still grow normally. Under different hydraulic loading rates, the lowest average removal rates of chemical oxygen demand (COD_Cr), total nitrogen (TN) and total phosphorus (TP) were 59.46%, 77.45% and 62.36% for 0.1 m-depth subsurface flow constructed wetlands, 59.24%, 32.02% and 57.89% for 0.6 m-depth subsurface flow constructed wetlands and 80.40%, 14.00% and 29.31% for 0.6 m-depth surface flow constructed wetlands, respectively. Based on the results of two years' performance, it was determined that it is feasible to simultaneously treat municipal wastewater and remediate desertification soil using municipal wastewater as the water source and fertilizer source, since the nutrient and structure of sandy soil improved obviously and each constructed wetlands had high removal efficiencies on COD_Cr, TN and TP in the summer and autumn.