Assessment of nutrients removal by constructed wetlands using reed grass (Phragmites australis L.) and vetiver grass (Vetiveria Zizanioides L.)

Abstract

Constructed wetland (CW) has been considered one of the low cost and effective wastewater treatment technologies for application in Vietnam. This paper attempted to evaluate the nutrient absorption ability of reed grass (Phragmites australis L.) and vetiver grass (Vetiveria Zizanioides L.) utilized in the vertical flow constructed wetland systems. Different hydraulic loading rates of 500 ml/min/m2, 1000 ml/min/m2and 1500 ml/min/m2were tried. The results showed that the nutrient removal percentage was highest at the hydraulic loading rate of 500 ml/min/m2. There was no statistically significant difference in nutrient removal between reed grass and vetiver at the same loading rate (p>0.05). Nevertheless, at the same loading level, the nutrient removal of the wetlands with plants was always higher than those without the plants (p<0.05). The effluent from the vertical constructed wetlands using plants all met the National technical regulation of surface water quality for agricultural irrigation purposes (column B1 in QCVN 08-MT: 2015/BTNMT). Thus, the constructed wetland using reed grass and vetiver grass would be quite a promising low cost technology for treatment of wastewater for irrigation purpose.