WASCO wishes to inform the public that water supplied from the Metolong dam which supplies the towns of Maseru, Roma, TY and Morija has been discolored from early February 2018. The discoloration is caused by existence of manganese in the water.
Manganese is a one of the most abundant naturally occurring mineral in the earth’s crust. The studies conducted before construction of the Metolong established that the Metolong catchment area has high levels of Manganese. Thus, the provision was made during the design stage to allow for the plant to treat manganese through aeration, and dosing of potassium permanganate. To this effect, a process line was constructed.
Causes of the current challenge
The changes in the colour of treated water are due to the different levels within the dam. Every dam has three different water quality layers. Due to the recent high temperatures the dam stratification became severe resulting in elevated manganese in raw water. This situation was aggravated by the recent river in-flows which agitated the dam water. Thus, high levels of manganese at all possible draw-off levels. There have also been challenges regarding faulty automation of some dosing system resulting in treatment ineffectiveness.
Measures taken to address the situation
WASCO has been hard at work to restore water quality. To this end;
- The monitoring of mineral content (with emphasis on manganese) in water was intensified and indentified required process changes were effected to optimise treatment. Subsequent to this, water that meets quality specifications is currently being produced at Metolong Water Treatment Plant. WASCO has already started flushing the supply system at strategic points in Maseru to remove the yellow water and expedite delivery of clear potable water to our customers.
Effects of manganese in treated water
In spite of the fact that the water did not meet aesthetic (standards (0.1mg/l), the levels of manganese in the treated water did not pose any health-related risks. WASCO regrets this recent delivery of aesthetically unacceptable water. Management assures the public of our commitment to supply safe potable water.