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 sources available at the mill; CD effluent, typically having a pH of 1-2 and E1 effluent (22), typically having a pH of 9-12 can be mixed 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 alkaline composition (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) the presence of a sulphide (20) or (ii) by carrying out the alkaline treatment at elevated temperature and pressure.