Answer:
iron
Your water might be affected by iron, which is a commonly-occurring constituent of drinking water. Iron tends to add a rusty, reddish-brown (or sometimes yellow) color to water. If the color is more black than red, your water might contain a combination of iron and manganese.
A process or set of rules to be followed in calculations or other problem-solving operations, especially by a computer.
Now why in the world anyone would want to do that....
Really!!!!