Phytoremediation by ornamental sunflower and its effects on the properties of drainage water

Abstract

Abstract due to legal restrictions on burning and burying sewage sludge in land and oceans, experts recommend using the sludge as fertilizer in agriculture to avoid the environmental problems associated with its disposal. Using sewage sludge in agriculture has limitations due to the presence of heavy metals, which can cause soil pollution and potentially harm animals and humans through the food chain. Furthermore, the use of sewage sludge can also lead to salinity and pollution of underground water by increasing the levels of nitrates and heavy metals in the soil water. The aim of this study was to explore the potential of using ornamental sunflowers for phytoremediation and to examine how this process affects the properties of drainage water. This research was conducted in the research greenhouse of Aburaihan campus of Tehran University. The sewage sludge was related to the sewage treatment plant in the south of Tehran and was prepared anaerobically and dewatered. Sewage sludge containing 0, 10 and 20 percent by weight of soil was done in three replications in the form of a completely randomized block design. Ornamental sunflower plant (Helianthus annuus) was used in this research. During the growth period, the water drains from the first watering after applying the treatments and the water drain from the last watering of the pots before harvesting the flowers were collected. The test results showed that the use of sewage sludge causes a significant increase in the concentration of Pb, Ni and Cd in the Ornamental sunflower roots and drainage water. But the concentration of these elements is lower than the standard limit and it shows that sunflower is able to purify these metals. Also, the amount of nitrogen and potassium in the water was increased.