Vietnam Japan University (VJU), Vietnam National University, Hanoi (VNU), Luu Huu Phuoc St., Nam Tu Liem Dist., Hanoi 101000, Vietnam.
Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology, Sydney, Broadway NSW 2007, Australia.
Sci Total Environ. 2020 Nov 1;741:140483. doi: 10.1016/j.scitotenv.2020.140483. Epub 2020 Jun 23.
It is well recognized that filter media play a crucial role in constructed wetlands (CWs) for decontamination of phosphorus (P)-rich wastewater. This study investigates the suitability of raw white hard clam shells (WHC) and white hard clam shells thermally modified at 800 °C (WHC-M800) as potential media to enhance P treatment performance in CWs. The results indicated that both WHC and WHC-M800 displayed appropriate physicochemical properties, such as high porosity, excellent hydraulic conductivity, and rich Ca content. WHC-M800 exhibited a superior P adsorption capacity (38.7 mg/g) to WHC (12.8 mg/g). However, the practical utilization of WHC-M800 as filter media in CWs may be compromised, due to certain limitations, for example: extremely high pH values in the post-adsorption solutions; high weight losses during calcination and adsorption processes; low mechanical strength; and intensive energy consumption. In contrast, the WHC demonstrated significant advantages of reasonably high P adsorption capacity, locally abundant availability, low cost, and marginal side effects. The fractionation of inorganic P of WHC and WHC-M800 revealed that Ca-bounded P was the most dominant binding form, followed by loosely bound P, Fe-P, occluded P, and Al-P. The present study demonstrates that recycling of WHC shells as a potential substrate in CWs provides a feasible method for upgrading P removal in CWs. Additionally, it helps to reduce waste WHC shells in a simple, cheap, and eco-friendly way, thus can double environmental benefits.
人们普遍认识到，过滤介质在用于去除富磷废水的人工湿地（CWs）中起着至关重要的作用。本研究探讨了原始白硬蛤壳（WHC）和在 800°C 下热改性的白硬蛤壳（WHC-M800）作为潜在介质在增强 CWs 中磷处理性能的适宜性。结果表明，WHC 和 WHC-M800 均具有适当的物理化学性质，如高孔隙率、优异的水力传导率和丰富的 Ca 含量。WHC-M800 表现出比 WHC（12.8mg/g）更高的磷吸附能力（38.7mg/g）。然而，由于某些限制因素，例如：后吸附溶液中极高的 pH 值；煅烧和吸附过程中重量损失高；机械强度低；以及能源消耗大，WHC-M800 作为 CWs 过滤介质的实际应用可能会受到影响。相比之下，WHC 具有合理的高磷吸附能力、本地丰富的可用性、低成本和较小的副作用等显著优势。WHC 和 WHC-M800 的无机磷分级表明，Ca 结合磷是最主要的结合形式，其次是松散结合磷、Fe-P、包裹磷和 Al-P。本研究表明，将 WHC 壳作为 CWs 中的潜在基质进行回收，为提升 CWs 中的磷去除提供了一种可行的方法。此外，它以简单、廉价和环保的方式帮助减少了废弃的 WHC 壳，从而可以带来双重的环境效益。
