Phytorestoration of Sewage Sludge from the Mangrove Landfill of «Bois des Singes» by Planted Filters of Pennisetum purpureum (Douala, Cameroon)

Human activities are causing wetland degradation. Macrophytes play an important role in the management of hydrosystems. They can therefore be used to restore a polluted environment. The aim of the study is to contribute to the phytorestoration of sewage sludge in nitrates, phosphates, cadmium, iron and lead from the Mangrove landfill of "Bois des singes" by planted filters of Pennisetum purpureum. A planted filter of P. purpureum was constructed. Sewages sludges samples were introduced into the device. Nitrates (NO3), phosphates (PO4), cadmium (Cd), iron (Fe) and lead (Pb) assays were carried out in water and plants at different levels of the filter (Settling basin B1, basin B2, basin B3, negative control and positive control) by absorption spectrophotometry flame atomic. The bioaccumulation and translocation factors as well as the bioaccumulation coefficient have been determined. The high contents of PO4 (4000 mg/l), NO3 (89 mg/l), Fe (5000 mg/l), Pb (20 mg/l) and Cd (0.08 mg/l) are greatly reduced by the filters at values below the tolerance threshold in B3 of 0.01 mg/l, 0.14 mg/l, 0.0002 mg/l, 0.0003 mg/l and 0.0003 mg/l respectively. The bioaccumulation factor shows that P. purpureum contained in barrels where the parameters are high is lead accumulator with a value of 1.305 (B2), hyperaccumulator of Fe and Cd with values of 10.05 (B2) and 13, 23 (B3). The leaf translocation is greater than 1 with Fe and Pb in the leaves of the boles. P. purpureum transfers Fe and Pb to the leaves. The planted filter of P. purpureum allows a restoration of this sewage sludge. This macrophyte extracts NO3, PO4, Cd, Fe and Pb and accumulates them in its vegetative system. P. purpureum cant be use to to restore the environment stressed by faecal sludge in the city of Douala.