Copper is one of those metals that seems to be evertwhere. The question have
for you is what is the level they are tying to meet?
Sources of copper can include that being brought into the facility by the
supply lines. If the water is aggressive, it can pick up enough copper to
exceed a tight limit. "Blowdown" from compressors have also found to contain
copper. General cleaning products have also found to contain copper. Biocides
in certain process chemistries can also contain copper as it is highly toxic
to fish and plant life. Brass fittings have also found to leach copper.
Since there are many sources of copper including the blue and green inks, I
would suggest that the printer first identify all sources of wastewater and
then begin a process of elimiantion by testing each one until the culprit is
found. The other apporach would be to seek a higher discharge limit,
especially if their limit is real low (0.1ppm-2 ppm).