Desalination pre‐treatment with LFNano

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Courtesy of EconoPure Water Systems, LLC

EconoPure Water Systems
EconoPure Water Systems designs and manufactures highly economical, scalable, low‐fouling. membrane systems. The Company leverages the proprietary low‐fouling nanofiltration. (“LFNano”) system consisting of a unique membrane element that is designed to avoid. particulate fouling, biofouling, and scaling. As the name suggests, the LFNano utilizes proven. nanofiltration (NF) membrane technology and applies proprietary processes to enhance. performance and decrease cost (both capital and operating). The LFNano requires much less. pre‐treatment and little or no process chemicals as compared to typical membrane systems. It. provides the exceptional quality treatment associated with membranes, without the hassle of. extensive pretreatment systems. The LFNano is an ideal solution for desalination pretreatment.

Introduction
Desalination is a growing water source that is becoming more important as population densities are leading to scarcity of fresh water supplies and greater pollution of these fresh water sources. There are many methods of desalinating seawater and brackish ground water and they all benefit from higher quality feed water to the desalting process step. The pre‐treatment process is how the feed water is conditioned prior to the main desalination step. Higher quality water can lead to less fouling on the main desalting step and save costs in maintenance and chemicals and replacement parts.

Problem Statement
Pretreatment has been called the black art of desalination as it is so critical to the success of a desalination plant. The famous case of the Tampa Bay desalination plant led to a reexamination of desalination in the United States. The pretreatment system at the Tampa Bay plant could not handle the variability in the seawater throughout the year and it was stressed to the point of failure. That plant was taken offline for 3 years and the pretreatment system was totally rebuilt. Stories like that are familiar in the desalination industry highlighting the critical nature of this process step. If the pretreatment is right, the plant is simple.

Existing Options
Typically the pretreatment step removes suspended matter leaving the dissolved matter to the main desalting step (either reverse osmosis (RO) membrane or thermal). However, a very high level of suspended solid removal is required for efficient operation of the desalting step. Even with removal of suspended solids, dissolved organics can still lead to significant fouling on an RO stage desalting step. Removing much suspended matter is simple and cheap but getting to the levels required by reverse osmosis membranes is complex and costly. Figure 1 below shows notionally the relative costs for removing much suspended matter and virtually all suspended matter.

Smaller particles are much more costly to remove and they impart more problems on the downstream stages. In Figure 1 the notional cost curve shows that removal of a lot of suspended solids from a source water is simple and inexpensive, shown as 90% removal and C1 as the cost. Conversely most desalting steps require far more removal to operate. This is shown as 99.5% and C2 as the cost, which is much higher than the cost (C1) to remove 90% of the suspended matter. The LFNano from EconoPure can operate with far more suspended matter in the water than current desalting steps and in many cases will not require any process ahead of it.

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