SEPARATION OF FIBER AND ASH IN DEINKING EFFLUENTS - A CASE-STUDY

Sludge disposal remains a problem for mills that recycle post-consumer waste. This report evaluates the feasibility of reducing sludge gener ation by removing suspended solids from spent deinking liquor. One-sta ge screening removed 35% of suspended solids from the deinking liquor, while a lower-cost experimental air-flotation technique removed 33%. Ash content of the retained solids was about 24%. Resuspension and res creening of the screened solids reduced the ash content to 16%. Repeat ing this cycle reduced the ash to 6%. The collected solids were high i n fiber content, had good papermaking characteristics, and could be re used in a mill furnish. The filtrate had a higher ash content and thus would be more amenable to land disposal. Computer analyses of four ex perimental techniques for separating fiber and ash from spent deinking liquor are presented.