RO System Configuration

Number of passes WAVE currently allows for a maximum of 2 passes 

The Flow Factor - this is used to simulate worst case scenarios in terms of rejection and energy demand. The number of pressure vessels for each stage 

The number of elements per pressure vessel WAVE restricts this number to between 1 and 8. 

The elements of interest. Standard Filmtec elements can be selected here. The specifications for each element are displayed by clicking on the Specs link. 

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The summary of the RO system configuration, flow and TDS at the system, pass and stage level... 

Hybrid RO System Configurations The two-pass and two-stage RO system configurations may be combined to achieve an optimum plant design and tailor desalination plant operation to the site-specific water source water quality conditions and product water quality goals. 

RO systems today accomplish the conversion either with a single or a double pass. From the Information provided to me by permeator and system manufacturers, and from discussions with individuals active in the Industry, it appears that about 60% of seawater systems use single pass conversion. One must add here that there are also differences in the configuration of RO membranes within the permeators. While there are others, the spiral wound and the hollow fiber designs truly command the market place today. Again, estimating, it appears that the hollow fiber design also has about 60% of the market. 

Reverse osmosis membranes for industrial applications are typically modularized using configurations that pack a large amount of membrane area into a relatively small volume. This makes the RO system more economical to use in that the system requires a smaller footprint, and membranes can be replaced in smaller modules rather than system wide. 

A significant amount of pretreatment is required to minimize fouling and scaling of the membranes in a CEDI system. Table 16.7 lists general feed water quality requirements for CEDI systems.15 21 Due to the stringent feed water quality requirements, most CEDI systems are preceded by RO. Common configurations used to pretreat CEDI feed water include the following 15... 

WAVE takes the system feed flow rate or system permeate flowrate (whichever one is specified) in the RO Configuration section as shown in Figure 10.12. The following inputs are used to specify an RO system ... 

Membrane systems consist of membrane elements or modules. For potable water treatment, NF and RO membrane modules are commonly fabricated in a spiral configuration. An important consideration of spiral elements is the design of the feed spacer, which promotes turbulence to reduce fouling. MF and UF membranes often use a hollow fiber geometry. This geometry does not require extensive pretreatment because the fibers can be periodically backwashed. Flow in these hollow fiber systems can be either from the inner lumen of the membrane fiber to the outside (inside-out flow) or from the outside to the inside of the fibers (outside-in flow). Tubular NF membranes are now just entering the marketplace. 

This interchangeability of components gives rise to very many RO configuration permutations and provides for a wide flexibility in system design, but may make the direct comparison of competing RO plants difficult at times. 

Although the first mechanism is intuitively, and for reasons of simplicity, preferred to the second one, there is no experimental evidence for excluding the latter. Theoretical evidence for preferring the former mechanism stems from a study by Jansen and Ros (1969), who performed non-empirical calculations on several configurations of a model system, viz. protonated carbon monoxide. They found that the linear +... 

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