Purifying Performance of the STEP of Mrirt (Natural lagoon)

M. Allaoui, ELH. Mohati M. Saadallah, A. El Harfi



The purifying system of the domestic lagoon sewage remains one of the most widely used processes in Morocco (81% of lagoon-type wastewater treatment plants) since it is the most technical solution which is suited to the economic and climatic conditions of our country.

Throughout this work, we tended to study the purifying performance of the wastewater treatment plant in the town of Mrirt, by measuring the parameters, which indicate the pollution degree, namely BOD5, COD and TSS. According to the results obtained from those parameters, we determined the causes of the non-conformity of rejection for the global parameters of pollution with respect to the unfiltered samples and proposed the solutions for the good purification of the STEP with a tertiary treatment, which is based on the physicochemical methods of the water discharged into the natural environments.

In the light of this work, the monthly results throughout the last two years (2012-2013) concerning the parameters of the raw and purified wastewater studied and discharged from the town of Mrirt have shown that:

* The average BOD5 which is recorded at the inlet and the outlet of the STEP is respectively 575 mg O2 / l and 159 mg O2 / l.

* The average TSS which is recorded at the inlet is 450 mg / l and at the outlet is 169 mg / l

* The average COD, which is recorded at the inlet and the outlet, is respectively 1015 mg O2 / l and 169 mg O2 / l.

On the basis of the obtained results, it can be said that the most suitable kind of the natural lagooning process in Morocco (the town of Mrirt) remains very sensitive to the various factors influencing the effluent yield of the STEP such as the accumulation of sludge at the level of the anaerobic basins, the climate change out of the seasons (temperature variation), residence period, volumetric and superficial load, the algal development ...etc.




Keywords: Mrirt, constructed wetlands; physico-chemical parameters; the levels of pollution; wastewater treatment plant; wastewater treatment; wastewater treatment.

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