Treatment of dairy process waters modelled by diluted milk using dynamic nanofiltration with a rotating disk module

• Published in: Journal of membrane science Vol. 282; no. 1; pp. 465 - 472
• Main Authors: Frappart, Matthieu, Akoum, Omar, Ding, Lu Hui, Jaffrin, Michel Y.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05-10-2006; Elsevier
• Subjects: Biomechanics; COD reduction; Dairy effluent; Dynamic nanofiltration; Mechanics; Physics; Rotating disk; COD reduction; Dairy effluent; Dynamic nanofiltration; Rotating disk
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2006.06.005

We have investigated the recovery by nanofiltration of lactose and milk proteins as well as carbon oxygen demand (COD) and ionic concentration reduction in dairy process waters simulated by UHT skim milk diluted 1:2 with an initial COD of 36,000
mgO
2
L
−1. The filtration system consisted in a 14.5
cm diameter metal disk (smooth or equipped with vanes) rotating near a circular Desal 5 DK membrane. At initial concentration, the permeate fluxes at a transmembrane pressure (TMP) of 4000
kPa and 45
°C ranged from 130
L
h
−1
m
−2 for a smooth disk at 1000
rpm to 230
L
h
−1
m
−2 using a disk with vanes at 2000
rpm. Permeate COD was minimum for this last case which gave the highest shear rates and decreased with increasing TMP from 60
mgO
2
L
−1 at 1400
kPa to 22 at 4000
kPa. In concentration tests at a TMP of 4000
kPa, at 2000
rpm with vanes, the permeate flux decayed with increasing volume reduction ratio (VRR) but was still 100
L
h
−1
m
−2 at VRR
=
7.5. The maximum VRR, reached using a disk with 6
mm vanes rotating at 2000
rpm, was 14.3, corresponding to 38% of dry matter. Permeate COD remained quasi independent of shear rate (rotation speed and disk type) until VRR
=
5 but increased more rapidly at lower shear rates for higher VRR, to reach 350
mgO
2
L
−1 at 2000
rpm with vanes. Comparison with recent data using same fluid, and same membrane, but installed in a vibrating system (VSEP), showed that the rotating disk yields better performance than the VSEP, due to its higher membrane shear rate.