I have searched the following sources and attributions:

1) Based off a 2007 Green Peace report, the total dissolved solids for Marilao river is 1765-3285 mg/L. However it did not mention the mineral composition of the said river, namely (from Chao Pan's and colleagues' article):

a) Chloride*

b) Nitrate (as N)*

c) Alkalinity as mg/L calcium carbonate

d) Water hardness as mg/L calcium carbonate

e) phosphate*

f) silicate (as silicon dioxide)

g) sulfate

*Primary components.

2) From the Philippine Journal of Science, there were no mentions on the composition of the Marilao river.

3) Water Quality assessments based on water management authorities have no report on the Marilao River or the Meycauayan River. However, they do have those from Laguna rivers or Rizal rivers (e.g.: Morong-Teresa river system). However, I doubt that the proportion of the minerals will be the same given that the geological composition of the two river systems (Morong-Teresa vs. Marilao-Meycauayan-Obando river systems) differ.

*What would be a good substitute if not the Marilao river?