Page 209 - Membranes for Industrial Wastewater Recovery and Re-Use

178 Membranes for Industrial Wastewater Recovery and Re-use

Figure 4.2 Flow specification dialogue box (ROPRO, Koch-Fluid Systems)

Process design variant
The process design variant (single pass, twin pass, etc.) normally has to be
specified at the start of the design process, and can be selected from a drop-down
menu or a dialogue window. The default selected is always the simple single-pass
plant. Obviously, the more complex the process design, the more information
required to be entered. Fig. 4.3 shows a two-stage concentrator RO plant
dialogue window.

Array design
The core of the RO process is the design of the array, in which the number of
stages and trains (i.e. rows of modules) must be defined. The definition of a single
stage, or bank, includes the number of pressure vessels (i.e. modules), the
number of membranes in each vessel and the membrane type. The latter can
range from low-selectivity, low-cost softening membranes to the more
permselective membranes used for seawater desalination. It is not possible, and
not sensible, to specify more than one membrane type in a single pressure vessel
or bank, although different membranes may be selected for different stages.
Membrane type is selected from drop-down menus that, of course, offer
membrane materials specific to the membrane supplier. In some cases, such as
ROPRO by Koch, the user can enter an approximate design flux, such that the
array can be calculated from this figure, the overall recovery and the properties
of the membrane selected. Otherwise, a preliminary value for the number of
elements per module can be calculated from the overall required permeate flow