REMOVAL OF AOX FROM BLEACH PLANT MILL EFFLUENTS BY PH SHIFT USING THE ALKALINITY/ACIDITY SOURCES AVAILABLE AT THE MILL

摘要

A process for removal of adsorbable organic chlorine (AOX) in which the acid-soluble AOX present in kraft chlorination(CD) effluents (12) are destabilized and converted to inorganic chloride by pH shift using the alkalinity and acidity sourcesavailable at the mill; CD effluent, typically having a pH of 1-2 and E1 effluent (22), typically having a pH of 9-12 can bemixed in various proportions to achieve a pH between 6.5-9.0 or the CD effluent is adjusted in pH to 6-11 with an alkalinecomposition (23) so that alkaline hydrolysis as well as precipitation of organic material occurs and the treated effluent (26)contains less AOX than present in the original untreated effluents; the AOX removal is enhanced substantially by (i) thepresence of a sulphide (20) or (ii) by carrying out the alkaline treatment at elevated temperature and pressure.