A Floating Island Treatment System for the Removal of Phosphorus from Surface Waters

本研究旨在设计、建造和测试一个中试规模的浮动模块化处理系统,并用以对美国佛罗里达州中部富营养化湖泊中的总磷(TP)进行去除。该处理系统由生物和物理-化学处理模块组成。用多种底物和水生大型植物组合构建了13种不同的中宇宙实验(mesocosm),分别测试了总磷(TP)和正磷(PO_4^(3-))的去除率及潜在的区域去除率。此外本研究对7种吸附介质进行了小型杯罐实验和柱实验,并对3种商业树脂进行了吸附能力的测试。完成这些独立的测试过程后,在佛罗里达中部的一个湖泊中,设计了一个浮岛处理系统(FITS)并运行了8个月。中宇宙实验对磷的平均去除率为40%～50%,平均去除量为5.0 g·m^(–2)·a^(–1)。其中沉水植物(SAV)系统和藻类洗涤器(AGS)效果最好,分别去除了20 mg·m^(–2)·d^(–1)和50 mg·m^(–2)·d^(–1)的磷,它们对磷的平均去除量分别为5.5 g·m^(–2)·a^(–1)和12.0 g·m^(–2)·a^(–1)。在吸附介质中,明矾渣(AR)的性能最佳,接触5 min后,PO_4^(3-)浓度降低了75%左右。在所测试的商品树脂中,PhosX树脂的去除效果最好,在30 min后去除了约40%的磷,60 min后去除了约60%的磷。在基线运行条件下展开实验,FITS对PO_4^(3-)的平均去除率为53%;使用PO_4^(3-)去除率的第50百分位和第90百分位以及FITS的环境足迹进行评价,结果表明系统的去除率分别为56%和86%;区域磷去除率在8.9～16.5 g·m^(–2)·a^(–1)之间。

The goal of this project was to design, build, and test a pilot-scale floating modular treatment system for total phosphorus （TP） removal from nutrient-impaired lakes in central Florida, USA. The treatment sys-tem consisted of biological and physical-chemical treatment modules. First, investigations of prospective biological and physical-chemical treatment processes in mesocosms and in bench-scale experiments were conducted. Thirteen different mesocosms were constructed with a variety of substrates and combi-nations of macrophytes and tested for TP and orthophosphate （PO4-^3） removal efficiencies and potential areal removal rates. Bench-scale jar tests and column tests of seven types of absorptive media in addition to three commercial resins were conducted in order to test absorptive capacity. Once isolated process testing was complete, a floating island treatment system （FITS） was designed and deployed for eight months in a lake in central Florida. Phosphorus removal efficiencies of the mesocosm systems averaged about 40%-50%, providing an average uptake of 5.0 g.m ^2.a ^1 across all mesocosms. The best-performing mesocosms were a submerged aquatic vegetation （SAV） mesocosm and an algae scrubber （AGS）, which removed 20 and 50 mg.m ^2.d ^1, respectively, for an average removal of 5.5 and 12.0 g.m ^2.a ^1 for the SAV and AGS systems, Of the absorptive media, the best performance was alum residual （AR）, which reduced PO4-^3 concentrations by about 75% after 5 min of contact time. Of the commercial resins tested, the PhosX resin was superior to the others, removing about 40% of phosphorus after 30 rain and 60% after 60min. Under baseline operation conditions during deployment, the FITS exhibited mean PO4-^3 removal efficiencies of 53%; using the 50th and 90th percentile of PO4-^3 removal during deployment, and the footprint of the FITS system, yielded efficiencies for the combined FITS system of 56% and 86%, respectively, and areal phosphorus removal rates between 8.9 and 16.5 g.m ^2.a ^1