Moura Daniel R, Silveira Maria L, O'Connor George A, Wise William R
Soil and Water Science Department, University of Florida, Gainesville, FL, USA.
J Environ Monit. 2011 Sep;13(9):2457-62. doi: 10.1039/c0em00785d. Epub 2011 Jul 15.
Rapid infiltration basins (RIBs) are effective tools for wastewater treatment and groundwater recharge, but continuous application of wastewater can increase soil P concentrations and subsequently impact groundwater quality. The objectives of this study were to (1) investigate the effects of reclaimed water infiltration rate and "age" of RIBs on soil P concentrations at various depths, and (2) estimate the degree (percentage) of sorption equilibrium reached between effluent P and soil attained during reclaimed water application to different RIBs. The study was conducted in four contrasting cells of a RIB system with up to a 25 year history of secondary wastewater application. Soil samples were collected from 0 to 300 cm depth at 30 cm intervals and analyzed for water extractable phosphorus (WEP) and oxalate extractable P, Al, and Fe concentrations. Water extractable P and P saturation ratio (PSR) values were generally greater in the cells receiving reclaimed water compared to control soils, suggesting that reclaimed water P application can increase soil P concentrations and the risk of P movement to greater depths. Differences between treatment and control samples were more evident in cells with longer histories of reclaimed water application due to greater P loading. Data also indicated considerable spatial variability in WEP concentrations and PSR values, especially within cells from RIBs characterized by fast infiltration rates. This occurs because wastewater-P flows through surface soils much faster than the minimum time required for sorption equilibrium to occur. Studies should be conducted to investigate soil P saturation at deeper depths to assess possible groundwater contamination.
快速渗滤池（RIBs）是用于污水处理和地下水回灌的有效工具，但持续应用废水会增加土壤磷浓度，进而影响地下水质量。本研究的目的是：（1）研究再生水入渗速率和快速渗滤池的“使用年限”对不同深度土壤磷浓度的影响；（2）估算在向不同快速渗滤池应用再生水期间，出水磷与土壤之间达到的吸附平衡程度（百分比）。该研究在一个具有长达25年二级废水应用历史的快速渗滤池系统的四个对比单元中进行。从0至300厘米深度以30厘米间隔采集土壤样本，并分析其中的水溶性磷（WEP）以及草酸盐提取的磷、铝和铁的浓度。与对照土壤相比，接受再生水的单元中的水溶性磷和磷饱和度比值（PSR）通常更高，这表明应用再生水磷会增加土壤磷浓度以及磷向更深层移动的风险。由于磷负荷更高，在有更长再生水应用历史的单元中，处理样本与对照样本之间的差异更为明显。数据还表明水溶性磷浓度和磷饱和度比值存在相当大的空间变异性，尤其是在以快速入渗速率为特征的快速渗滤池单元内。出现这种情况是因为废水磷流经表层土壤的速度比发生吸附平衡所需的最短时间快得多。应开展研究以调查更深层的土壤磷饱和度，从而评估可能的地下水污染情况。
