Investigation of the Effect of Vetiver plant and retention time on the BOD reduction in the floating constructed wetland with free water surface flow

In the free water surface flow (FW-SF) constructed wetlands with plant cultivated on floating platforms¡ the large number of microorganisms living around the plants roots create a suitable environment for wastewater treatment. To study the effect of Vetiver plant and sewage retention time in treatment efficiency of such systems¡ six ponds as a pilot in the Karoun sugarcane Agroindustrial¡ located in Khuzestan province¡ 20 km away from the city of Shushtar was built. Units were built in parallel with each other (length 3m¡ width 1m and height 0.8 m). Agricultural wastewater was obtained from the washing process of sugarcane for 3 months from January to March 2013. From are six ponds constructed under the Vetiver plants¡ three units floating and three units without plants (control) were considered. The average BOD concentration of the wastewater entering the unit was 98±3.57 mg/l and retention times investigated were ¡ 5 and 7 days. During the experiments¡ the concentration of BOD per unit of input and output was analyzed using SAS software. The results of the analysis showed significant differences between plant and non-plant systems¡ including retention times. The constructed wetland system with plant cultivated and the retention time of 7 days in March had the highest removal rate at 58.97%. In better words¡ optimum conditions for maximum removal rate of agricultural wastewater of the Karoun sugarcane Agro-industrial using the floating constructed wetlands systems was with vetiver cultivated and though the retention time of 7 days.