Physicochemical and microbiological quality of the treated wastewater of the Marrakech WWTP for irrigation

Abstract

The urban district of Marrakech has a wastewater treatment plant of activated sludge type. Water treated by this WTTP is intended for the irrigation of golf courses. Tertiary treatment can extract any undesirable substance not removed by the steps before. The aim of this work is to characterize the physico-chemical and microbiological quality of the treated water  and to assess the effectiveness of tertiary treatment. The pH varies between 7.1 and 7.7 which is in the range recommended by both the Moroccan and the USEPA standards. The COD content fluctuates between 24.87 and 52.33 mg O₂ / l, which is below the limit value of 60 mg O₂ / l recommended by the French legislation. Concentrations of BOD₅ range is between 1.1 and 4.21 mg O₂ / l which is widely below the standard of 30 mg O₂ / l recommended by the WHO and USEPA for the reuse of treated wastewater. For the SM, the value of 30 mg / l is the threshold set by both the WHO, USEPA and French law. The values ​​of SM fluctuate between 2.86 and 8.46 mg / l which are perfectly in accordance with the recommended standard. The content of nitrates does not exceed 5 mg N / l is lower than the limit set by WHO and the Moroccan standard of 30 mg N / l. The TP content is between 1,88 and 6,23 mg P / L compared with the range 6-20 mg / l agreed by WHO. The microbiological analysis, including research faecal coliforms show that the values ​​obtained are below standard 200, 250 and 1000 UF / l respectively recommended by the USEPA, the French legislation and concomitantly the Moroccan standard and WHO . However, the parasitology examination especially of nematodes attests their total absence, showing the effectiveness of the tertiary treatment. Finally, the water at the outlet of the WWTP of Marrakech, destinated for irrigation has a physicochemical and microbiological quality compliant for irrigation.