Des études portant sur l’épuration des eaux usées domestiques ont été menées sur une filière de trois bassins en série de lagunage à microphytes à la station expérimentale de l’Institut International d’Ingénierie de l’Eau et de l’Environnement (2IE). Cette filière comporte : un bassin anaérobie (BA), un bassin facultatif (BF) et un bassin de maturation (BM). Des mesures d’indicateurs de qualité ont été effectuées pendant dix mois sur des échantillons prélevés suivant une fréquence bihebdomadaire pour certains et hebdomadaire pour d’autres. Les rendements épuratoires moyens atteignent 66 % pour les MES, 81 % pour la DCO et 87 % pour la DBO5. Le résiduel de MES de l’effluent traité répond, dans 76 % des mesures, aux normes de rejet recommandées par la directive de l’Union Européenne (
Waste stabilization ponds (WSP) are considered to be one of the main methods for municipal wastewater because of their advantages over other methods (conventional treatment) relating to treatment effectiveness, system flexibility and simplicity, and cost (Arthur, 1983; Mara, 1976; Mara and Pearson, 1986; Silva, 1982). Moreover, it has long been accepted that tropical climates provide an ideal environment for the natural treatment of sewage in ponds.Since 1989, the 2IE (International Institute for water and Environmental Engineering) wastewater treatment plant in the city of Ouagadougou (Burkina Faso) has been investigating the performance of pilot-scale systems in order to establish regional design parameters and removal efficiencies. Several experiments have been carried out on pond series with different configurations and operational characteristics aiming to improve the design, operation and performance of waste stabilization ponds in Sahelian climate conditions. The purpose of the present study was to evaluate the efficiency of a new series of three stabilization ponds.The series was composed by one anaerobic pond (AP), one facultative pond (FP) followed by one maturation pond (MP). The characteristics (depth, area, volume and hydraulic retention time) were respectively 2.6 m, 69.7 m2, 181.2 m3, and three days for the AP, 1.4 m, 415.3 m2 and 581.4 m3 and 9.5 days for the FP, 0.9 m, 336.9 m2, 303.2 m3 and 5.5 days for the MP. The ponds were constructed with concrete to ensure water tightness. Field studies indicated a wide fluctuation in the biochemical oxygen demand (BOD5) loading applied. The average volumetric organic load ranged from 104 to 225 g BOD5 m‑3j‑1 with an average load of 105.2 g BOD5 m‑3j‑1 for the AP, the average surface BOD5 load on the FP was 117 kg BOD5/ha/j.The series was monitored for ten months from October 2004 to July 2005. The assessment involved an intensive program of sampling and analysis. The composite samples (obtained daily by mixing equal volumes of grab samples collected) were taken from the influent and effluent of each pond twice per week. Global physico-chemical parameters (T°, pH, Dissolved Oxygen (DO), conductivity ) were measured in situ. Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD) were analyzed according to standard methods. Suspended solids (SS) were determined gravimetrically after filtration through Whatman GF/C glass fiber filters and drying at 105°C. Total Kjeldahl Nitrogen (TKN) and ammonia nitrogen (AN) were analyzed according to AFNOR methods. Nitrate nitrogen (NT), total phosphorus (TP) and orthophosphate (OP) were determined by HACH methods. Faecal coliforms (FC) were counted by layer technique using the chromocult coliform agar, helminth eggs and protozoan cysts were determined by sodium acetate formalin (SAF) adapted method.Results showed during the study period average removal rates of 66% for SS, 87% for filtered BOD5, and 81% for COD. For COD and BOD5, removal performances were relatively constant over the study period with ranges of (60,9% ‑ 96,1%) and (65,6 ‑ 6,8%), respectively. In 83.8% of filtered BOD5 measures (n = 68) on the final effluent, BOD5 removal efficiency were higher than 80%. However, for SS removal efficiency, it indicated a wide fluctuation. The same fluctuation was observed on SS concentration on the final effluent, with a variation coefficient of 34.3%. Effluent SS concentrations from the series varied between a minimum of 4 mg/L and a maximum of 326 mg/L with average of 110 mg/L. The higher values of SS were observed during the warm period (March-April) corresponding to the abundance of algal proliferation in facultative and maturation ponds. In this period, effluent SS concentrations were higher than the influent ones, leading to negative efficiencies for these ponds. Despite this disturbance due to algal proliferation, the final effluent quality met the European Union (EU) quality requirements, i.e suspended solids concentration
