Ocean chemistry and mixing processes, marine life
conditions, other present or proposed outfalls in the
vicinity, and relevant aspects of areawide waste treatment
management plans and programs, but not of convenience
to the discharger, shall for the purposes of this section, be
considered in determining the effects of such discharges.
Toxic and hard-to-treat substances should be pretreated at
the source if such substances would be incompatible with
effective and economical treatment in municipal treatment
plants