Your water might be affected by iron, a commonly occurring constituent of drinking water. Iron tends to add a rusty, reddish brown (or sometimes yellow) color to water, and leaves particles of the same color.
Water leaving our homes generally goes either into a septic tank in the back yard where it evaporates or seeps back into the ground, or is sent to a sewage-treatment plant through a sewer system.
No, but it can cause problems. Depending on where you live, maybe you've heard of acid rain.
Acid precipitation affects stone primarily in two ways: dissolution and alteration. When sulfurous, sulfuric, and nitric acids in polluted air react with the calcite in marble and limestone, the calcite dissolves.
Eutrophication is the process by which a body of water acquires a high concentration of nutrients, especially phosphorus and nitrogen. These typically promote excessive growth of algae.