BOD5 attenuation from contaminated waters by using vetiver grass in surface flow constructed wetland

In the free water surface flow (FW-SF) constructed wetlands, a large number of micro organisms that live around the roots of plants create a suitable environment for wastewater treatment. To study the effect of Vetiver plant and sewage retention time in treatment efficiency of such systems, nine ponds in the Karoun sugarcane Agro-industrial located in the city of Shushtar was built. Units, in parallel with each other and each unit with length 3m, width 1m and height 0.8 meters. Continuously, agricultural wastewater from the washing process of sugarcane from December 2013 until May 2014 was established. Three of the units filled with soil and were transplanted with vetiver (S), three units were cultivated with vetiver on the floating platform (F) and three units were kept unplanted as control (C). The average BOD5 concentration of the wastewater entering the unit was 115±15.69 mg/l and retention times of experiments were 3, 5 and 7 days. During the experiment, the concentration of BOD5 per unit of input and output measurements 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 May had highest value of the average removal rate equal to 68.48 percent. In other words, optimum conditions for maximum BOD5 removal rate of Karoun sugarcane Agro-industrial wastewater in floating constructed wetlands systems was with vetiver cultivated and in the retention time of 7 days.