How to Bring your High-Purity Water Pretreatment Systems into the 21st Century
By Nissan Cohen and Shlomo Sackstein
Are changes needed in water systems used to prepare feedwater for reverse osmosis (RO) systems? Or, are the standard pretreatment systems adequate? Can treatment improvements come by further fine tuning of existing systems, or is it necessary to use different kinds of technologies?
The authors’ observe that pretreatment systems for reverse osmosis (RO) feedwater have not changed appreciably in the last 30 years. As the RO polyamide (PA)-type membrane has become a common standard, this article will focus on pretreatment for these types of systems.
The standard of softening ion exchange (IX) in collaboration with activated carbon (AC) is still the preferred option today. Softeners are used to stop scale build up in the membranes, and the AC is used to stop oxidization damage to the sensitive PA membrane by chlorine (1).
Even though this combination has proved itself over the years, the system has limitations and disadvantages. Presently, the number of viable options is limited, especially, if the site has problematic mineral species or periodic high microbiological levels.
A new combination of technologies will be presented in this article; a system that has none of the draw backs of the traditional softener-carbon duo. The new system operates with no need for regeneration, without organic media, and without chemicals. This new system operates reliably and robustly without sophisticated software or control loops, and has vast advantages in low maintenance and life-cycle costs.
Water systems in the biopharma industry provide modules configured to remove hardness and chlorine/chloramine (2) so as not to block or perforate the delicate PA RO membranes found in these systems.
In addition, if the system is to be used in the biopharma industries, these pretreatment component modules are also called upon to remove or reduce microbial contamination (1).
Traditional pretreatment configurations have been used for decades with considerable costs in salt storage and preparation, rinse and wastewater effluent drainage, brine disposal, chemical usage for regeneration, and sanitization. These complex systems need regular maintenance and an expert eye to identify trends and possible causes of failure, when and if they occur.
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