Performance of wetland roof with Melampodium paludosum treating septic tank effluent

• Published in: Desalination and water treatment 2014, Vol.52 (4-6), p.1070-1076
• Main Authors: Thanh, Bui Xuan, Hai Van, Phan Thi, Tin, Nguyen Thanh, Hien, Vo Thi Dieu, Dan, Nguyen Phuoc, Koottatep, Thammarat
• Format: Article
• Language: English
• Subjects: Hydraulic loading rate (HLR); Melampodium paludosum; Organic loading rate (OLR); Wetland roof
• ISSN: 1944-3986; 1944-3986
• DOI: 10.1080/19443994.2013.826323

Wetland roof (WR) system was developed to apply for building terrace and top roof in the urbanized area of Ho Chi Minh City. This study aims to improve the green area of the city and to treat domestic wastewater through a shallow horizontal subsurface constructed wetland that is located in a household roof. The pilot-scale unit of horizontal subsurface flow WR system with Melampodium paludosum, an indigenous emerging plant in Vietnam, was experimented at the average hydraulic loading rate (HLR) of 338 m3/ha d (∼36 kg COD/ha d) corresponding to HRT of 18 h. The treatment performance was not significantly different for rainy and sunny days at various HLRs. It was observed that the average removal efficiency of COD was 77–78% or 20–28 kgCOD/ha d for both sunny and rainy days. It is apparent that nutrient removal was greatly achieved as indicated by TN removal efficiency of 88–91% or 17–20 kg TN/ha d. In addition, TP removal reached 72–78% or 1.6 kg TP/ha d for different HLRs. The treated effluent could comply with the standard limits of Vietnam national technical regulation for domestic wastewater. It was also observed that the growth rate of M. paludosum was 0.1 cm/day in length. The ratio between nitrogen uptake by plants over nitrogen removed by WR was 0.13, while the higher ratio of 0.68 was obtained for the case of phosphorus. The temperature of WR units was 4 ± 1°C lower than that on concrete floor that likely help saving energy for building cooling if applying WR on the top roof. Based on the experimental results obtained to date, the WR system would be a promising system for domestic wastewater treatment especially for urbanized city, where green area is of high demand.