Brackish Water Reverse Osmosis
Brackish water is defined as a water supply that has a total dissolved solids (TDS) content ranging from 50 to 10,000 milligrams per liter (mg/l). Water from a brackish water treatment system is most often used for potable water, purified water (food & beverage, pharmaceutical) or industrial process water. Purified and industrial process water may require additional treatment by ion exchange or other processes to produce the quality of water required by user. Examples of industrial process water applications are:
• Make-up water for low and high-pressure boilers used in power generation.
• Make-up water for boilers where the steam is used as part of the process for production of petrochemicals.
• Make-up water for the ultra pure water loop in the production of semiconductors and other related electronic equipment (e.g., DVD, disk drives, etc.).
Reverse osmosis membranes play an important part in producing treated water, which meets the end-use customer needs for potable, purified water and industrial applications. This technology is combined with other unit operations to meet demanding water quality requirements that cannot be achieved using only membranes.
The selection of products for brackish water applications is dependent on several variables that the OEM or end-use customer may influence. In addition, the intended use for the product water and characteristics of the feedwater source influence selection. A few of the factors influencing selection are:
• Pretreatment – most membrane systems will have conventional filtration (sand, dual or multi-media). However, using microfiltration (MF) or ultrafiltration (UF) prior to the reverse osmosis system can remove colloidal and suspended foulants better than conventional treatment.
• Feedwater source – ground water sources (i.e., wells) are typically lower in colloidal and suspended matter than surface water sources. Some sources, such as tertiary effluent can have high levels of bacteria and biological activity in addition to colloidal and suspended foulants.
• Energy costs – many locations have a high cost for power usage. The choice of element will also influence capital costs in the area of high-pressure pumps and motors.
• High salt rejection (low salt passage) – since many membrane systems are combined with ion exchange or continuous de-ionization (CDI), membrane choice is influenced by these unit operations.
The high degree of automation enables FilmTec to produce an element with 400 square feet of active membrane area. Dimensionally, all 8 inch diameter element are very similar. But, by automating the prepping of materials and assembly of the element, FILMTEC is able to achieve higher volume and leaf efficiencies. Higher volume efficiency is achieved through very accurate material cutting, leaf spacing, and glue line placement. Higher leaf efficiency is due to shorter leafs which allows the permeate to flow to the product water tube with less flow resistance.
Higher active area IS NOT achieved through use of thinner materials or winding the elements tighter! Higher active area IS achieved through higher precision of material prepping, glue line placement, and automated assembly.
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