Abstract:
This experiment was divided into 2 phases. The first period was to select 2 suitable vetiver grass ecotypes in order to implement for the second period. Six vetiver grass ecotypes (Kumphaeng Phet2, Sri Langka, Songkhla3, Surat Thani, Prajuab Kiriklhan and Ratchaburi) were grown in plastic tank with low concentration wastewater (LCW) (average BOD, TKN and TP were 55.88, 40.297 and 6.022 mg/I, respectively) for 8 weeks. The results indicated that the highest removal percentage of BOD, TP and ortho-PO(subscript 4) was found in Songkhla3 and Surat Thani ecotypes which were 80.07-81.06, 16.38-16.81 and 10.39-12.87%, respectively. Moreover, the high growth rate and nutrient (TN and TP) accumulation were found in those two ecotypes. The second period was to study the efficiency of two selected ecotypes in municipal wastewater treatment. The experiment was conducted by cultivating Songkhla3 and Surat Thani ecotypes in plastic container of 0.85x1.55x0.50 meters each with LCW (average BOD, TKN and TP were 44.28-58.92, 34.731-42.144 and 4.838-5.482 mg/I, respectively) and high concentration wastewater (HCW) (average BOD, TKN and TP were 90.12-94.88, 41.025-52.806 and 5.892-6.657mg/I, respectively). The study was divided into 3 periods of 8 weeks each, using 7-day, 5-day and 3-day detention times and continuous flow system. The results indicated that the removal percentages of different detention time and wastewater concentration were significantly different. The highest removal percentage was found in 7-day detention time. The highest removal percentage of BOD, TKN, TP and ortho-PO(subscript4) were found in HCW with average percentage of 90.54-91.46, 61.01-62.48, 17.78-35.87 and 15.40-23.46%, respectively. The highest removal percentage of NH (subscript3)-N removal percentage was found in LCW with average percentage of 50.22-58.62%. The removal percentage of different ecotypes was not significantly different. However, the study showed that the experimental sets with vetiver grass had higher removal percentage than a control set (without plant). Surat Thani ecotype tended to have higher root growth than Songkhla3 ectyped. However, the biomass increment of Songkhla3 ecotype was highest in HCW whereas Surat Thani ecotype was highest in LCW. According to nutrient accomulation in shoot and root, it was found that generally nutrient accumulation increased with wastewater concentration. The highest nutrient accumlation in root was found in 7-day detention time. In conclusion, the overall results suggested that the optimal condition vetiver grass cultivated with floating platform technique in municipal wastewater treatment should design at 7-day detention time and planted with Surat Thani ecotype. However, if wastewater had high BOD and nutrients, Songkhla3 could be planted.