Study on the performance of the wastewater stabilisation pond of Boujaad, Morocco

The wastewater stabilisation ponds system of the city of Boujaad was constr ucted and put into operation in 1992. The main objectives of this plant are to prevent pollution of water resources and the environment by wastewater discharges, and to save fresh water by reusing treated wastewater for irrig ation purposes. Within the period March 1997-March 1998 a comprehensive ana lysis of both the raw and the treated wastewater at a number of different s ampling points was carried out in order to evaluate the treatment efficienc y of the plant. The results of these investigations showed an average raw w astewater flow of 1600 m(3)/d, which is well below the design flow of 2500 m(3)/d. With average treated wastewater suspended solids (SS) content of 56 mg/l the SS removal rate has been determined to be about 65%. If compared to the anticipated Moroccan wastewater standards for direct wastewater disc harge into receiving water bodies as stipulated in the anticipated Moroccan Standards (AMS 1996) the wastewater analysis results showed COD and BOD5 V alues below these foreseen Moroccan wastewater discharge standards. The ana lysis results of SS, TKN and total phosphorous (P-tot) were slightly above these Moroccan standards. In view of the microbiological wastewater charact eristics the treated effluents of the Boujaad wastewater stabilisation pond s (WSP) respond to the WHO directive with respect to wastewater to be used for unrestricted irrigation (category A). Taking into consideration the CEC directive for wastewater generated by wastewater treatment plants and disc harged to the environment, the efficiency of the Boujaad WSP is relatively low with respect to SS removal, the removal of organic matter (expressed by BOD5 and COD) and the removal of nutrients (expressed by TKN and P-tot). T his relatively low efficiency may be caused by the already highly diluted i ncoming raw wastewater, which again is caused by the effect of significant infiltration of groundwater into the sewerage network.