What Causes Brown Discharge from a Sandfilter?

[lenin_yuweh]

Do anyone know what would cause brown discharged from sandfilter?

The sandfilter is compose of gravel and anthracite.

Would reducing agent particulary SO4 react with antracite forming brown discharged?

The sandfilter is used to reduced copper and clear water. However, in this instant, the inlet of sandfilter was clear but after sandilter, the water turned light reddish brown but the copper was not affected.

 

[chemisttree]

Are you sure the anthracite was not contaminated with Leonardite? At high pH Leonardite dissolves as a brownish red compound. It is good for your plants if the metal contents are acceptable, BTW. If the anthracite can be oxidized it is likely to produce quinones that will appear to look like tea at higher pH (8 or so) and if ammonia is present.

 

[lenin_yuweh]

According to the downstream team, the anthracite was not contaminated with Leonardite. I forgot to mention that the order of the sandfilter is anthracite, sand, pebbles, then gravel.

Would the oxidize antracite produced quinones at a pH of 4-7? How about if MnO- is present? Would only a small content of oxidizing agent like SO4- is needed to oxidized the anthracite?

 

[chemisttree]

SO₄^-2 is not a reducing agent. It's not an oxidizing agent either.

So the sandfilter didn't lower the concentration of copper but it did impart a color to the water. Is the color pH sensitive?