Last April 25, 2016, some of our customers in the southern portion of our concession area observed discoloration in their water supply.
The discoloration was due to the presence of high manganese level in the raw water supply that we are getting from Laguna Lake. Since the onset of the strong El Niño beginning the last quarter of 2015, the water level in Laguna Lake has been steadily decreasing. The high temperature brought on by the summer season further exacerbated the quality of raw water in the lake.
The sharp decline in the water level in Laguna Lake causes more sediments, such as manganese and other mineral deposits, to enter our water treatment facility.
To fully contain the level of dissolved manganese in the water supply, we did system adjustments in our treatment facility and also conducted flushing activities in areas where there have been reports of water discoloration. These measures enabled us to address the discoloration within 48 hours since the increase in manganese level occurred.
Except for the discoloration, the water supply distributed to our customers is still within the parameters set by the Philippine National Standards for Drinking Water (PNSDW).
Maynilad further assures that increased levels of manganese may affect the water’s turbidity, taste and odor but, health-wise, is not a cause for alarm. Under the PNSDW, manganese is classified not under “Inorganic Chemicals with Health Significance” but under “Physical and Chemical Quality for Acceptability Aspect”—because when mixed with chlorine, it may make the water yellowish.
Manganese forms naturally in the air, soil and water and is an essential trace element necessary for humans, plants and animals. At a level of 0.02 mg/L, manganese will form coatings on water pipes that may slough off as black sediments; hence, we have cautioned our customers to cover their faucets with a clean cloth. The PNSDW states that the permissible level of manganese in drinking water is 0.4 mg/L.
According to the World Health Organization’s 2011 Guidelines for Drinking-water Quality, it would require exposure to high levels of manganese over a long period before manganism develops.
We regret the inconvenience that the temporary water discoloration has caused our customers in the south. We wish to assure them that we are constantly monitoring the characteristics of the water in Laguna Lake, and we have the necessary technologies in place to continue producing water that meets the PNSDW.