Removal of a synthetic organic chemical by PAC-UF systems. II: Model application

This paper describes several application potentials with a recently develop ed model for predicting the synthetic organic chemical (SOC) removal by pow dered activated carbon (PAC) adsorption during ultrafiltration (UF) and dis cusses the removal mechanism. The model was successfully applied, without a ny modification, to dead-end mode operation as well as to cross-Row mode op eration, validating the assumption of the internal diffusion control mechan ism and the continuously-stirred-tank-reactor (CSTR) concept. Even when UF was operated in a cross-how mode, PAC added was re-circulating in suspensio n for only a short time. Then, solute uptake look place mostly by PAC immob ilized in membrane tubes not only for dead-end operation but also for cross -flow operation. Therefore, cross-flow operation did not have any advantage regarding the SOC mass transfer on PAC in UF loop over dead-end operation. The model simulation implied that pulse PAC addition at the beginning of f iltration cycle resulted better SOC removal than continuous PAC addition. H owever, for the pulse PAC addition mode, the model predicted somewhat lower effluent SOC concentration than the observed values, and the benefit of pu lse PAC application in terms of reducing SOC over its continuous dosage was not confirmed. Longer detention time of PAC dosed in a pulse than continuo usly dosed PAC could possibly further decrease internal diffusivity. (C) 20 00 Elsevier Science Ltd. All rights reserved