Effects of biostimulation on the phytoremediation of crude oil-polluted aquatic ecosystem by water hyacinth (Eichhornia crassipes [Mart.] Solms)

This study investigated the effects of inorganic fertilizer (N₁₅P₁₅K₁₅ and urea) amendments on petroleum degradation and uptake by water hyacinth (Eichhornia crassipes). The experiment was conducted in two phases. In phase 1, 100g of water hyacinth were grown separately on experimental units (fresh borehole water) spiked with petroleum at concentrations of 0mg/l, 20mg/l, 40mg/l and 60mg/l. In phase 2, experimental units were spiked with petroleum at 4 different concentrations (0mg/l, 20mg/l, 40mg/l and 60mg/l) and then were randomly assigned fertilizer (N₁₅P₁₅K₁₅) at 3 different concentrations (0mg/l, 6mg/l and 10mg/l) such that each crude oil treatment had the three fertilizer amendments. A similar procedure was repeated using urea as biostimulant. Each phase of the experiment lasted six months. Total petroleum hydrocarbon (TPH) in water column and water hyacinth were determined using APHA methods. Concentration of TPH in water column, TPH absorption by water hyacinth, relative degradation of TPH in water column and percentage absorption of TPH by water hyacinth varied significantly (p<0.05) among the biostimulation units regardless of the initial petroleum concentration. At 40mg/l and 60mg/l initial crude oil concentrations, the water hyacinth in the control absorbed significantly (p<0.05) higher hydrocarbons (6.84±0.18mg/kg and 7.13±0.16mg/kg for treatments spiked with 40mg/l and 60mg/l crude oil respectively) than the treatments amended with inorganic fertilizers. The degradation of petroleum hydrocarbons followed first-order kinetic model. This study showed that phytoremediation of crude oil by water hyacinth and inorganic fertilizer amendment to enhance crude oil degradation is achievable.