Main Article Content
Constructed wetlands (CWs) have been applied to treat various wastewater types including domestic wastewater, livestock wastewater, industrial wastewater and acid mine drainage with the advantages of low cost, environmentally-friendly technology and high treatment efficiency. Mining wastewater with the high content of heavy metals often causes negative impacts on the ecosystems and human health. In this study, the capacity of using limestone, hydrolyzed rice husk as filter materials and the CWs planted with Caladium bicolor to treat iron and manganese in artifical wastewater treatment are evaluated. The wetland model has the size of length x width x height of 50 cm x 15 cm x 20 cm. 10 liters of the synthetic wastewater were used and initial Fe and Mn concentrations varied from 5, 10, 15, 20 and 25 mg/L. The results showed that limestone and hydrolyzed rice husk with the weight ratio of 5 : 2.5 (kg) had good ability to remove Fe and Mn with treatment efficiencies of approximately 99.8% after 144 hours. During a 24-hour retention time, the Fe and Mn concentrations in the wastewater decreased rapidly in CWs and the initial Fe and Mn concentrations affected treatment performance. When the initial Fe and Mn concentrations were below 20 mg/L, treatment efficiencies of Fe and Mn reached about 99% after 144 hours in the CWs and Fe and Mn concentrations met the national regulation QCVN 40: 2011/BTNMT, column B. The study highlights the potential applications of C. bicolor in CWs with the use of natural limestone and hydrolyzed rice husk as substrates in treatment of iron and manganese-contaminated wastewater.
Keywords: Constructed wetlands, Caladium bicolor, limestone, rice husk, iron, manganese.
 E. Chockalingam, S. Subramanian, Studies on Removal of Metal Ions and Sulphate Reduction Using Rice Husk and Desulfotomaculum nigrificans With Reference to Remediation of Acid Mine Drainage, Chemosphere, Vol. 62, No. 5, 2006, pp. 699-708, https://doi.org/10.1016/j.chemosphere.2005.05.013.
 A. Singh, D. B. Pal, A. Mohammad, A. Alhazmi, S. Haque, T. Yoon, N. Srivastava, V. K. Gupta, Biological Remediation Technologies for Dyes and Heavy Metals in Wastewater Treatment: New Insight, Bioresource Technology, Vol. 343, 2022, pp. 126154, https://doi.org/10.1016/j.biortech.2021.126154.
 J. Vymazal, The Use of Constructed Wetlands with Horizontal Sub-surface Flow for Various Types of Wastewater, Ecological Engineering, Vol. 35, No. 1, 2009, pp. 1-17, https://doi.org/10.1016/j.ecoleng.2008.08.016.
 J. Garcia, D. P. L. Rousseau, J. Morat, Ó, E. L. S. Lesage, V. Matamoros, J. M. Bayona, Contaminant Removal Processes in Subsurface-Flow Constructed Wetlands: A Review, Critical Reviews in Environmental Science and Technology, Vol. 40, No. 7, 2010, pp. 561-661, https://doi.org/10.1080/10643380802471076.
 J. Vymazal, L. Kröpfelová, Wastewater Treatment in Constructed Wetlands with Horizontal Sub-Surface Flow, Springer, Netherlands, 2008.
 H. Wu, J. Zhang, H. H. Ngo, W. Guo, Z. Hu, S. Liang, J. Fan, H. Liu, A Review on the Sustainability of Constructed Wetlands for Wastewater Treatment: Design and Operation, Bioresource Technology, Vol. 175, 2015,
pp. 594-601, https://doi.org/10.1016/j.biortech.2014.10.068.
 M. C. Perdana, S. Hadisusanto, I. L. S. Purnama, Implementation of a Full-scale Constructed Wetland to Treat Greywater from Tourism in Suluban Uluwatu Beach, Bali, Indonesia, Heliyon, Vol. 6, No. 10, 2020, pp. e05038, https://doi.org/10.1016/j.heliyon.2020.e05038.
 C. A. C. Iii, M. K. Trahan, Limestone Drains to Increase pH and Remove Dissolved Metals from Acidic Mine Drainage, Applied Geochemistry, Vol. 14, No. 5, 1999, pp. 581-606, http://dx.doi.org/10.1016/S0883-2927(98)00066-3.
 B. T. K. Anh, N. V. Thanh, N. M. Phuong, N. T. H. Ha, N. H. Yen, B. Q. Lap, D. D. Kim, Selection of Suitable Filter Materials for Horizontal Subsurface Flow Constructed Wetland Treating Swine Wastewater, Water, Air, & Soil Pollution,
Vol. 231, No. 88, 2020, https://doi.org/10.1007/s11270-020-4449-6.
 H. Ye, Q. Zhu, D. Du, Adsorptive Removal of Cd (II) from Aqueous Solution Using Natural and Modified Rice Husk, Bioresource Technology, Vol. 101, No. 14, 2010, pp. 5175-5179, https://doi.org/10.1016/j.biortech.2010.02.027.
 B. T. K. Anh, Research on the Treatment of Heavy Metals (Fe, Mn) in Coal Mining Wastewater by Biological Conversion Method Combined with Constructed Wetland, Final Report of the VAST Project Coded UDPTCN04/18-20, 2020, https://vast.gov.vn/web/vietnam-academy-of-science-and-technology/science-and-technology-research-projects/, (accessed on: October 15th, 2021).
 A. Sdiri A, T. Higashi, Simultaneous Removal of Heavy Metals from Aqueous Solution by Natural Limestones, Applied Water Science, Vol. 3, 2013, pp. 29-39,
 A. Sdiri, S. Bouaziz, Re-evaluation of Several Heavy Metals Removal by Natural Limestones, Frontiers of Chemical Science and Engineering, Vol. 8, 2014, 418-432, https://doi.org/10.1007/s11705-014-1455-5.
 J. Odom, J. R. Postgate, R. J. Singleton, The Sulfate-Reducing Bacteria: Contemporary Perspectives, Springer, New York, 2013.
 S. Wu, P. Kuschk, A. Wiessner, J. Müller, R. A.B Saad, R. Dong, Sulphur Transformations in Constructed Wetlands for Wastewater Treatment: A review, Ecological Engineering, Vol. 52, 2013, pp. 278-289, https://doi.org/10.1016/j.ecoleng.2012.11.003.
 C. Dalai, R. Jha, V. R. Desai, Rice Husk and Sugarcane Baggase based Activated Carbon for Iron and Manganese Removal, Aquatic Procedia, Vol. 4, 2015, pp. 1126-1133, https://doi.org/10.1016/j.aqpro.2015.02.143.
 E. G. Abdel, M. A. Kamal, R. Cote, Effect of Temperature on the Performance of Limestone/Sandstone Filters Treating Landfill Leachate, American Journal of Environmental Sciences, Vol. 3, No. 1, 2007, pp. 11-18, https://doi.org/10.3844/ajessp.2007.11.18.
 B. Lesley, H. Daniel, Y. Paul, Iron and Manganese Removal in Wetland Treatment Systems: Rates, Processes and Implications for Management, Science of The Total Environment, Vol. 394, No. 1, 2007, pp. 1-8, https://doi.org/10.1016/j.scitotenv.2008.01.002.
 B. T. K. Anh, Study on The Combined System Using Limestone and Constructed Wetland to Remove Manganese, Zinc and Iron from Mine Drainage, VNU Journal of Science: Natural Sciences and Technology, Vol. 32, No. 1S, 2016, pp. 9-14.
 J. Opitz, M. Alte, M. Bauer, S. Peiffer, The Role of Macrophytes in Constructed Surface-flow Wetlands for Mine Water Treatment: A Review, Mine Water and the Environment, Vol. 40, 2021, pp. 587-605, https://doi.org/10.1007/s10230-021-00779-x.
 L. Guo, T. J. Cutright, Metal Storage in Reeds from an Acid Mine Drainage Contaminated Field, International Journal of Phytoremediation, Vol. 19, 2017, pp. 254-261, https://doi.org/10.1080/15226514.2016.1216073.
 N. T. H. Ha, B. T. K. Anh, The removal of Heavy Metals by Iron Mine Drainage Sludge and Phragmites australi, IOP Conference Series: Earth and Environmental Science, Vol. 71, 2017, pp. 012022,