Membrane processes for the recovery of dairy cleaning-in-place solutions

The recovery of dairy cleaning-in-place (CIP) solutions contributes to savi ng chemicals, water and energy, maintaining cleaning efficiency, and reduci ng pH variation and volume of waste stream. The aim of this study was to co mpare different processes for this particular operation. Industrial cleanin g solutions were ultrafiltered (300 kg.mol(-1)): membrane performances were CIP-type dependent. One particular type (alkaline) of CIP solution was tre ated using decantation, centrifugation and cross-flow filtration (0.1 mu m microfiltration [MF], 300 and 15 kg.mol(-1) ultrafiltration [UF], inorganic and organic nanofiltration [NF]). Centrifugation, decantation and 0.1 mu m MF only removed particles, UF slightly reduced the soluble chemical oxygen demand (COD); and NF more largely. Increasing the volume reduction ratio ( VRR) (up to 50 here) reduced the volume of sludge, but resulted in a higher fouling (although always moderate) and a higher organic content of the per meate. NF is a proper process: membrane performance stabilization when VRR increased, satisfactory flux (> 100 L.h(-1).m(-2) at 70 degrees C) and the best pollution reduction. A cascade with pretreatment of the CIP alkaline s olution by 0.1 mu m MF was detrimental to NF performances. (C) Inra/Elsevie r, Paris.