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

Abstract

The recovery of dairy cleaning-in-place (CIP) solutions contributes to saving chemicals, water and energy, maintaining c1eaning efficiency, and reducing pH variation and volume of waste stream. The aim of this study was to compare different processes for this particular operation. Indus- trial c1eaning solutions were ultrafiltered (300 kg-mol:'): membrane performances were CIP-type depen- dent. One particular type (alkaline) of CIP solution was treated using decantation, centrifugation and cross-f1ow filtration (0.1 um microfiltration (MF), 300 and 15 kg-mol-' ultrafiltration (UF), inorganic and organic nanofiltration (NF)). Centrifugation, decantation and U.I um 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 perme- ate. NF is a proper process: membrane performance stabilization when VRR increased, satisfactory flux (> 100 L·h-1·m-2 at 70 C) and the best pollution reduction. A cascade with pretreatment of the CIP alkaline solution by 0.1 um MF was detrimental to NF performances. © InralElsevier, Paris waste stream c1eaning-in-place / microfiltration / ultrafiltration / nanofiltration