Agricultural Soil Fertilizing Potential of Dry Faecal Sludge from Treatment Plants in Burkina Faso

Abstract

The dry faecal sludge (DFS) are potential sources of organic fertilizers because of their high content in nutrients and organic matter, critical for plants growth and soil health maintaining. In Burkina Faso, the DFS are processed in faecal treatment plants. However, after drying, the DFS are most often dumped in the nature without any control or directly used as fertilizer without any idea of their potential risks for human health and the environment. This investigation aimed at physico-chemical and toxicological characterization of the DFS from faecal treatment plants according to the duration of their storage. For this purpose, DFS samples were collected in three (3) faecal treatment plants in Ouagadougou and one in Bobo Dioulasso, in Burkina Faso. The measurements were carried out on pH (H 2 O), organic matter content, major nutrients (N, P, K), trace elements (Na, Ca and Mg) and metallic trace elements. Indifferently to the faecal treatment plants and the duration of the storage, the DFS showed strong acidity (4.85 ± 0.13 et 6.53 ± 0.10) and low content in total elements (Na < 200 mg/kg; Ca < 4000 mg/kg et Mg < 2000 mg/kg). the contents in major nutrient were between 1.08% ± 0.37% and 2.22% ± 0.56% for N and for P it were 8595.24 ± 281.33 mg/kg and 18687.55 ± 1570.68 mg/kg; and 519.40 ± 31.16 mg/kg et 1469.46 ± 1110.16 mg/kg for K. The C/N ratio (9.37 ± 0.33 - 12.17 ± 0.60) showed a good mineralization status of the DFS and its high content of organic matter (22.12% ± 6.83% &#224; 40.97% ± 9.99%). Values recorded of the trace metallic elements showed there were no risk of contamination when used as fertilizers: (103.9 ± 2.00 mg/kg < Cu < 137 ± 25.69 mg/kg); (710.13 ± 18.97 mg/kg < Zn < 922.30 ± 7.04 mg/kg); (33.03 ± 1.65 mg/kg < Pb < 152.40 ± 19.40 mg/kg); (1.34 ± 0.17 mg/kg < Cd < 1.76 ± 0.04 mg/kg); (34.34 ± 0.27 mg/kg < Ni < 52.32 ± 3.60 mg/kg) et (771.15 ± 18.36 mg/kg < Cr < 1697.83 ± 55.11 mg/kg). The results indicated a high fertilizer potential of the DFS after addressing the issue of their acidity.