Study the Effectiveness of the Natural Lagoons for Removal of Organic Matter, Nutrients and Fecal Coliform from Urban Domestic Wastewater under Arid Climate (Morocco)

摘要

Morocco is one of the countries most affected by the scarcity of water resources and the poor distribution of rain- fall. Natural lagoon is the most widely used treatment process in Morocco. Indeed, Morocco is a sunny country throughout the year. The lagoon system requires minimal effort in operation and maintenance. Moreover, this sys- tem is the best process for removing bacteria indicators. For these reasons, a study of the purification performance of natural lagoons during five years, located in Chichaoua region (Morocco) was carried out. The lagoon system was monitored for five years, with measurements taken every three months at the input and output of the system. It received a hydraulic loading rate (HLR) between 1171 and 2760 m3 with an average of 2053 m3/day. The ob- tained results show the removal of 37 of TSS, 63 of BOD5, 60 of COD, 61 of NH4+, 37 of TP, and 6.5 log units of coliforms during the mentioned monitoring period. Thus, the effluent values do not always comply with the Moroccan water quality requirement for irrigation reuse. Additionally, the statistical analyses confirm the pres- ence of a strong linear correlation between almost all variables in the lagoon output. Therefore, the performance efficiency of the lagoon in removing organic matter and nutrients was significantly (p 0.05) affected by the seasons in this study. At the end of this study a complementary treatment before the reuse of treated wastewater, was proposed.