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The study team has run the 500 m2 pilot wetland aiming to figure out optimum design parameters such as: balancing requirements of hydraulic conductivity, hydraulic headloss, filtration efficiency and plant growth. | Vietnam Journal of Science and Technology 56 (2C) (2018) 165-171 DESIGN OF WETLAND SYSTEM FOR WASTEWATER QUALITY IMPROVEMENT AT FORMOSA HA TINH STEEL COMPANY Viet-Anh Nguyen1, *, Anh Thi Kim Bui2, Giang Ngo Hoang1 1 Institute of Environmental Science and Engineering, Hanoi University of Civil Engineering, 55 Giai Phong, Ha Noi 2 Institute of Environmental Technology, VAST, 18 Hoang Quoc Viet, Ha Noi * Email: anhnv@nuce.edu.vn Received: 10 May 2018; Accepted for publication: 22 August 2018 ABSTRACT After a marine life disaster in central Viet Nam in 2016 due to poorly treated steel industry wastewater and pipe cleaning solutions, the Formosa Steel Corporation has been improved their wastewater treatment systems. Besides, an effluent polishing and buffer pond – wetland system has to be built. The study team has run the 500 m2 pilot wetland aiming to figure out optimum design parameters such as: balancing requirements of hydraulic conductivity, hydraulic headloss, filtration efficiency and plant growth. The pilot wetland was filled with different kind of lime stone, peanut gravel and sand, running with flow rate 49.5-122.4 m3/h. The pilot test results have provided appropriate design parameters for the 4.3 ha Formosa wetland: Subsurface flow constructed wetland cells CB1, CB2, CB3 placed in series, with maximum horizontal flow rate 122 m3/h, unit hydraulic headloss 22.8cm/100m, followed by free water surface flow wetland cell CB4. The main filtration media selected for wetland cells CB1, 2, 3 was lime stone with diameter 50-100 mm (60 cm depth), where supporting layers for plant vegetation were coarse sand (20cm depth) and peanut gravel of 5-10 mm diameter (10 cm depth). The full scale 10 ha pond-wetland system now is in operation, proving design configurations of the team. Keywords: constructed wetland, filter media, headloss, hydraulic conductivity. 1. INTRODUCTION Constructed wetland (CW) is eco-friendly technology that utilizes aquatic plants for wastewater .
