Nanomembranes - Nanotechnologies for Water Environment Applications - page 371

plant was commissioned in 2005 and the raw water is pumped to the plant from one of
the 54 wells located throughout the City. The new membrane softening process treats
approximately two-thirds of the raw water, while the remaining one-third is treated by
lime softening. The recovery of the semi-permeable “softening membranes” is 85%.
This facility is the first large-scale plant operating successfully with no chemical
pretreatment, saving nearly $1 million annually in operating costs and reducing safety
risks as well (FES, 2006).

&O
62
S +&2
¯ &D
¼ 0J

3UHVVXUHEDU

Figure 12.1 Influence of transmembrane pressure on the retention of the ions.

Antiscalants,
pH adjustment

Disinfection

Cartridge

Degasifier

Groundwater

Air

Membrane
filtration unit

To distribution
network

Concentrate to
disposal

Figure 12.2 Typical nanofiltration softening plant.