Major Developments in Water Treatment Technology

To meet the industrial sector's demand for high-purity water, two key technologies have been developed in industrial water treatment in recent years, each bringing about a breakthrough in water treatment systems.

In the 1960s and 70s, the water quality requirements of the industrial sector could be met by chemically regenerated ion exchange technology. Due to its limited application at the time, the long-term effects of using chemical agents received little attention.

In early water treatment systems, the mixed-bed ion exchange stage was placed as a separate unit after cation and anion exchange as a subsequent treatment process. With increasing application requirements, chemically regenerated ion exchange systems clearly became limited, with the main issue being the high TOC content they leaked. Compared to more recent technologies, these systems used large amounts of chemical regeneration agents, required continuous treatment of chemical wastewater, and were complex and costly to operate.

In the 1970s and 80s, with increased awareness of reducing chemical agent use, new process methods were sought in industrial water treatment, resulting in the renewed application of reverse osmosis technology. Reverse osmosis (RO) uses membrane technology to replace cation/anion exchange units in pre-desalination systems. However, this new technology did not perform well in its initial applications. RO had high requirements for pretreatment, while the overall water treatment system tended towards simplification.

As the electronics industry's requirements for pure water quality (including reduced TOC content) increased, water treatment technology continued to advance, and RO was seen as a solution. With improvements in pretreatment processes and the development of more advanced RO membranes, the problems encountered in the early stages of RO application were gradually overcome.

Over time, RO gradually gained acceptance, and subsequent ion exchange technologies, such as countercurrent regeneration designs, full-bed ion exchange, and the development of specialized resins, also developed accordingly. Due to the widespread application of these new processes, costs have decreased, but RO/mixed-bed systems still offer some economic advantages compared to current chemically regenerated ion exchange systems, and there remains a certain demand for these technologies.

RO/mixed-bed systems meet the diverse requirements of industrial sectors for high-purity water quality. They can treat insoluble impurities to a few parts per billion and also reduce TOC content. Regardless, industrial applications still rely on mixed-bed technology as the final stage of desalination. The use of chemicals in the mixed-bed stage and the associated facility requirements mean that the benefits of RO (Reverse Oxidation) are not fully realized. Further reductions in chemical usage have spurred a second technological revolution.

Electrodeionization (EDI), commonly known as electro-deionization, was first developed for laboratory work over 40 years ago as a non-chemical process. Recent developments in EDI technology have made it possible to completely eliminate dependence on chemical regeneration agents, and it also offers a range of other benefits.