Effect of applying rhizobacteria and fertilizer on the growth of Ludwigia octovalvis for arsenic uptake and accumulation in phytoremediation

The aim of this study was to investigate the effect of applying a six-rhizobacterial consortium and nitrogen phosphate potassium (NPK) fertilizer in inorganic arsenic (arsenate) phytoremediation using Ludwigia octovalvis (Jacq.) Raven plants. The experiment included control L. octovalvis plants and three phytoremediation treatments with L. octovalvis plants, namely an arsenic (As) concentration of 39 mg kg−1 only, the addition of a six-rhizobacterial consortium at 2% (v/v) with an As concentration of 39 mg kg−1 and the addition NPK fertilizer at 0.02% (w/w) with an As concentration of 39 mg kg−1. In the As phytoremediation treatment with the presence of As only, plants showed signs of phytotoxicity such as wilting and senescent leaves. L. octovalvis grew well until the end of exposure (Day 42) in the phytoremediation treatment with 2% rhizobacteria consortium or with 0.02% NPK fertilizer addition. The As phytoremediation treatment with 2% rhizobacteria showed the highest removal percentages of bioavailable As (89%), total extractable As (78%) and As in the leachate of the reed beds (98%) resulting in lower As uptake by L. octovalvis than in the other two phytoremediation treatments. This indicates that the bioremediation process played a role in the treatment with 2% rhizobacteria. The fresh weight of L. octovalvis biomass in treatment with 0.02% NPK fertilizer increased by almost five-fold compared with the As only treatment. The effectiveness of phytoremediation in terms of As uptake at Day 42 reached 49.8% in the phytoremediation treatment with 0.02% NPK fertilizer addition. It was the highest than in the other two phytoremediation treatments. In conclusion, NPK fertilizer addition gave the best results in As uptake using L. octovalvis plants in terms of the effectiveness of phytoremediation.