Oum Azza DWTP, Rabat, Morocco

 

Background

This treatment plant was built within the framework of a project to enhance the drinking water supply system to the coastal corridor that runs from Rabat to Casablanca, using water from the Sidi Mohamed Ben Abdellah reservoir. The system owner and operator is ONEE (Morocco’s National Water and Electricity Office).

Acciona Agua was responsible for the design, construction and commissioning of the facility, described below.

Raw water quality

The water from the reservoir is slightly alkaline and presents relatively large variations from year to year. Turbidity also varies from up to 250 NTU in rainy periods to clear water in dry periods. The temperature of the water ranges from 11ºC to 26ºC.

Raw water pumping station

Located near the dam, this station is equipped with 6 centrifugal pumps with the capacity to lift 5.67 m3/s to a minimum level difference of 150 m. These horizontal, split-chamber pumps are driven by 2,800 kW motors and each pump is capable of lifting up to 1.44 m3/s, depending on the number of pumps in operation and the height of the water surface in the reservoir.

The water is sent a distance of 4.5 km through a subterranean pipeline to the DWTP.

Electricity substation for raw water pumping

The substation is located near the raw water pumping station. It is connected to the ONEE supply grid at 40 kV and transforms the voltage to feed the pumping station. This outdoor substation is equipped with two 28 kVA 40/6 kV transformers.

Treatment plant

The plant is designed to produce a nominal flow of 18,000 m3/h or 432,000 m3/
day of water fit for human consumption. This water complies with all Moroccan and World Health Organisation (WHO) quality requirements.

The plant has a modular design and each process stage is made up of a number of lines operating in parallel,
a layout which facilitates maintenance.

The plant design enables the capacity to be doubled, i.e., up to 10 m3/s, and space has been reserved to incorporate ozonation and granular activated carbon stages in the future.

The buildings are strategically arranged to optimise functionality. A highlight is the operations building in the form of a water molecule, with three modules representing the oxygen atom and the two hydrogen atoms. In addition to the laboratory and workshops, this building also houses the automated control system.

The raw water is pumped into a concrete inlet tank with a volume of 2,000 m3, from where it is distributed by gravity to two treatment lines, each with a treatment capacity of 2.5 m3/s. Each line is equipped with its own pipe-installed flowmeter.

 

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Published in: FuturENVIRO #45 November 2017