Arias C A, Del Bubba M, Brix H
Department of Plant Ecology, University of Aarhus, Nordlandsvej 68, DK-8240 Risskov, Denmark.
Water Res. 2001 Apr;35(5):1159-68. doi: 10.1016/s0043-1354(00)00368-7.
Sorption of P to the bed sand medium is a major removal mechanism for P in subsurface flow constructed reed beds. Selecting a sand medium with a high P-sorption capacity is therefore important to obtain a sustained P-removal. The objective of this study was to evaluate the P-removal capacities of 13 Danish sands and to relate the removal to their physico-chemical characteristics. The P-removal properties were evaluated in short-term isotherm batch-experiments as well as in 12-week percolation experiments mimicking the P-loading conditions in constructed reed bed systems. The P-removal properties of sands of different geographical origin varied considerably and the suitability of the sands for use as media in constructed reed beds thus differs. The P-removal capacity of some sands would be used up after only a few months in full-scale systems, whereas that of others would persist for a much longer time. The most important characteristic of the sands determining their P-removal capacity was their Ca-content. A high Ca content favours precipitation with P as sparingly soluble calcium phosphates particularly at the slightly alkaline conditions typical of domestic sewage. In situations where the wastewater to be treated is more acid, the contents of Fe and Al may be more important as the precipitation reactions with these ions are favoured at lower pH levels. The maximum P-sorption capacities estimated using the Langmuir-isotherm plots did not correspond to or correlate with the actual amount of P removed in the percolation columns. Hence, the Langmuir-isotherm does not estimate the P-removal capacities of sands. It is suggested that a suitable quick method of screening a selection of potential media for P-removal potential is to perform simple removal isotherm studies using water with a similar chemical composition as the wastewater to be treated. This method will not provide a direct estimate of the P-removal capacity that can be obtained in full-scale systems, but it is a means of comparing the relative performance of potential media.
磷在床沙介质上的吸附是潜流人工芦苇床中磷去除的主要机制。因此，选择具有高磷吸附能力的沙介质对于实现持续的磷去除很重要。本研究的目的是评估13种丹麦沙子的磷去除能力，并将去除效果与其物理化学特性相关联。通过短期等温线批量实验以及模拟人工芦苇床系统中磷负荷条件的12周渗滤实验来评估磷去除特性。不同地理来源的沙子的磷去除特性差异很大，因此这些沙子作为人工芦苇床介质的适用性也不同。在全尺寸系统中，一些沙子的磷去除能力仅在几个月后就会耗尽，而其他沙子的磷去除能力则会持续更长时间。决定沙子磷去除能力的最重要特征是其钙含量。高钙含量有利于与磷沉淀形成难溶性磷酸钙，特别是在生活污水典型的微碱性条件下。在待处理废水酸性更强的情况下，铁和铝的含量可能更重要，因为在较低pH值下与这些离子的沉淀反应更有利。使用朗缪尔等温线图估算的最大磷吸附容量与渗滤柱中实际去除的磷量不对应或不相关。因此，朗缪尔等温线不能估算沙子的磷去除能力。建议一种筛选潜在介质磷去除潜力的合适快速方法是使用与待处理废水化学组成相似的水进行简单的去除等温线研究。这种方法不会直接估算全尺寸系统中可获得的磷去除能力，但它是比较潜在介质相对性能的一种手段。
