Feasibility study of faecal sludge treatment by constructed wetlands in Sahelian context: Experiments with Oryza longistaminata and Sporobolus pyramidalis species in Ouagadougou

In Urban areas of Burkina Faso, there are essentially on-site sanitation systems, constituted of latrines and septic tanks. Faecal sludge produced by these utilities are actually rarely treated and just spilt in the environment. So, there is a need to develop sustainable treatment solutions, to preserve local populations health, water resources and environment. In order to investigate rustic sludge treatment, 12 experimental sludge treatment reed bed systems, planted with two local species: Oryza longistaminata (OL) and Sporobolus pyramidalis (SP), were constructed and monitored in Ouagadougou, Burkina Faso. The goal was to assess the potential of OL and SP planted beds to treat fecal sludge in Sahelian climate. A hydraulic load of 20–26 cm/week corresponding to 15.8–21.1 kg TSS/m2/year (62.6–83.5 kg DM/m2/year) was applied on all the beds for 120 days. The characterization of raw fecal sludge was assessed using physicochemical parameters (DM, TSS, NO3−-N, NO2−-N, NH4+-N, PO43−-P, TP, and COD). Allometric parameters of plants on each bed were also monitored. The high contents of COD, nutrients and salinity could be particularly associated with the plants wilting and death, especially for OL. The threshold values of 1900 mg/L for COD, 174.5 mg/L for NH4+, 19.9 mg/L for PO43− and 4400 mS/cm for conductivity induced sensitive variation of plant behaviors were highlighted for Oryza longistaminata.