DOES THE SEMICONTINUOUS ACTIVATED-SLUDGE (SCAS) TEST PREDICT REMOVAL IN SECONDARY-TREATMENT

The semi-continuous activated sludge (SCAS) test was formalized by the U.S. Soap and Detergent Association in 1965. The SCAS procedure has a lso been adopted by the Organization for Economic Cooperation and Deve lopment (OECD) as a test for inherent biodegradability and by the U.S. EPA as a test guideline (40CFR 835.3120) under the Toxic Substances C ontrol Act. To investigate whether the SCAS test may be used to predic t removal in full-scale activated sludge treatment systems, we first c ollected all available SCAS data for organic chemicals, and then retri eved data from full-, pilot-or bench-scale continuous-feed activated s ludge (GAS) studies for the chemicals that had SCAS data. The intersec ted file was subjected to statistical analysis. Conclusions were as fo llows: (i) SCAS data were strongly clustered at high (>90 %) removal; (ii) for SCAS removal >90 %, it is probable that removal in the field will be >50 %; (iii) however, for SCAS removal <90 % adequate treatabi lity cannot be predicted with confidence. Published by Elsevier Scienc e Ltd.