Sedimentation Practices for Paper Industry Wastes

Sedimentation practices for 27 treatment plants handling waste waters from paper industry mills are reported with data on raw waste suspended solids and BOD. Percentage removals of suspended solids by settling vary from 65% to 98% with a mean value of 90%. Percentage of removals of BOD vary from 10% to 90% with a mean value of 43%. Raw waste waters are widely variable as to quality characteristics of BOD and suspended solids, even among mills producing similar products. In many cases sedimentation alone is extremely effective in the purification of paper industry waste water. No correlation could be found on an over-all industry basis or on a mill product basis between purification results and the calculated design factors of detention time, overflow rate, and solids loading, for operating plants. Sedimentation design should be considered a separate problem for each mill.