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The Application of Membrane Technology in Industrial Wastewater Treatment by Thomas Roehl, from PROCESS ‘Process Industry’. Water is indispensable in industrial production; therefore, the ability to provide industrial water that meets the specific requirements of different production processes is an important factor in determining investment decisions. The rational use of water resources is the foundation for sustainable global development and steady economic growth. As production process efficiency and product quality standards continue to improve, the corresponding water treatment technologies also need to be optimized and innovated. The integration of production processes with water treatment technologies represents a huge challenge for the manufacturing process. Globally, as the population grows and industrial demand increases, freshwater supply is becoming increasingly scarce, and its cost is also rising. At the same time, chemical plants also face the situation of increasingly strict requirements regarding wastewater discharge. Therefore, the role of new water treatment technologies becomes extremely crucial. Around the world, municipal wastewater treatment plants are being used more and more as a source for water supply. According to statistics from the Reclaimed Water Association, in the United States alone, the amount of wastewater treated by such plants is increasing at a rate of 15% per year. Due to the decentralized nature of water treatment and recycling within factories, it is difficult to quantify the amount of water treated in these locations. However, according to estimates from equipment suppliers, global wastewater treatment is growing at a rate of 15% to 20% per year. Different factories use various water treatment methods; even factories that produce the same products may employ different approaches to wastewater treatment. Although the methods of water treatment vary, their basic principle remains the same: to separate out useful compounds for reuse, while removing substances that are harmful to the environment so as to prevent them from causing damage; thereafter, this wastewater is further treated to meet specified discharge standards. Wastewater treatment methods include mechanical filtration and separation, chemical-biological treatment, clarification, flotation, and evaporation, among others. Advances in the application of membrane technology in nanofiltration plants for treating dark wastewater. Most plants are now equipped with basic water treatment facilities, but to achieve water regeneration, more advanced treatment processes are required, such as the use of microfiltration (MF) or ultrafiltration (UF) membranes. In the final stage of water treatment, nanofiltration (NF) or reverse osmosis (RO) systems can be added depending on specific needs. For companies that require water of higher purity, such as those involved in pharmaceutical and semiconductor manufacturing, it is necessary to add ion exchange or electro-deionization equipment. On average, depending on the type of molecule, reverse osmosis can remove 90% to 98% of the solids dissolved in water, while ion exchange or electrodeionization systems can remove an even greater amount of these dissolved solids, achieving concentrations as low as 2 ppm or less. Christ Company’s Liproline system can be used to purify wastewater generated in the production process of biologic products, and it enables fully automatic intermittent or continuous treatment. If product recovery as well as the recycling of other resources are required alongside water treatment, then using membrane technology for water treatment offers significant advantages. When water resources are not in short supply, the recycling of products becomes a very important factor. Enviro-Chemie has applied the Envopur treatment unit in a range of different industrial processes, including the textile industry, the printing and dyeing industry, the production of various compounds, and the glass and ceramics industry. Membrane technology is usually combined with other physicochemical processes for wastewater treatment, such as ion exchange, absorption, and precipitation. As one of Mexico’s largest oil refineries, Pemex selected the ZeeWeed ultrafiltration membrane system from Zenon Company for its wastewater treatment facilities in Minatitlán. This water treatment technology enables the provision of high-quality water for use in cooling towers and the refining process. Membrane technology can also be used for water desalination, which has created a new market that is continuing to expand rapidly. As the main component of filtration systems, the market competition for filter membranes is extremely fierce. As filter membrane performance improves and costs decrease, users have more options when choosing filter membranes and suppliers; therefore, this fierce competition will continue unabated. According to a report by Koch Membrane Systems, there has been a significant increase in interest in ultrafiltration and reverse osmosis for new projects. Five years ago, the company’s initial research focused on ultrafiltration and reverse osmosis; today, however, about 90% of its preliminary research is dedicated to evaluating ultrafiltration and reverse osmosis systems in public water treatment plants, with the aim of reusing water while eliminating pollutant emissions. USfilter’s Apex system is designed specifically for pharmaceutical or other high-purity applications; it is a modular, comprehensive, automatically operated pure water system. Water treatment solutions tailored to local conditions. General Electric Infrastructure is a newcomer to the water treatment industry; after three years of extensive research, the company discovered great potential in water recycling and decided to enter the water treatment market. In 2004, Siemens acquired USFilter. Over the past five years, USFilter has installed more than a dozen large-scale membrane separation systems in its plants for water treatment and reuse, including products such as Memcor, Microfloc, and General Filter. In the previous decade, the number of installations was very low. Also in 2004, ITT Industries, which supplies pumps, valves, and other systems for the power industry, established Aquious-PCI Memtech by adding membrane separation products acquired through mergers and acquisitions to its existing business. Aquious plans to strengthen its position in the field of membrane separation desalination through various new projects, including those aimed at providing drinking and industrial water for the Middle East region. In addition to these companies, Ondeo Industrial Solutions, a subsidiary of SUEZ, Hager + Elsner, Linde-KCA-Dresden under Linde, Veolia Environment, Gromtmij, DHV Water, and Membrana all offer their own solutions for this growing market. In addition to the rapid growth in the use of membrane technology for desalination or water resource recycling, there is also an increasing number of end-use applications based on membrane separation technology; this helps to reduce pollutant emissions while simultaneously enabling resource conservation. For example, a wastewater biological treatment plant equipped with the cross-flow microfiltration membranes from WAT-membratec can remove radioactive pollutants from wastewater. In the chemical industry, valuable compounds can also be recovered for reuse by installing membrane filtration systems. After wastewater treatment is completed, the remaining liquid can be removed from the system through pneumatic flushing, which **reduces the amount of water needed for flushing and cleaning, thereby significantly improving the production efficiency of the process. The use of polypropylene membranes allows the operation to be unaffected by pH value. Obviously, the rising costs of water supply and wastewater treatment in industrial production have become the main driving force behind the installation of membrane separation wastewater treatment systems in many regions. But before that, membrane separation technology was not widely accepted. Sometimes process water and wastewater contain ground powder, as in the glass industry; in such cases, or when high-pressure cleaning or friction is required, a membrane separation system needs to be installed. In such cases, UFI-TEC can provide solutions; for example, in factories that use wet screening for corundum, installing a microfiltration system can enable the treatment and recycling of grinding wastewater at a rate of 10 m3/h. As a result, the amount of process water used is reduced, wastewater treatment costs are lowered; by using the most appropriate process water, the quality of the products improves, and wastewater discharge meets the specified requirements. Reverse osmosis systems are capable of producing water with low TDS. Taking the treatment of sludge from pig farms as an example, purifying such sludge requires multiple purification steps, ranging from the separation of insoluble solids to the separation of various soluble components using reverse osmosis membranes. UFI-TEC Company provides one of the purification techniques for this purpose. In addition to clean water, its products also include fertilizers of different qualities. WAT-membratec also provides a similar treatment system that utilizes the principle of producing biogas from agricultural waste as a starting material to process industrial fermentation media. In these two application technologies, the use of membranes allows liquid waste that would otherwise be discharged directly and cause harm to the environment to be treated so as to be regenerated, or to have its useful components reused. Another application prospect for membrane separation technology lies in ultra-pure water production systems. For example, a major semiconductor manufacturer in China has installed Liqui-Cel membrane contactors from Membrana Company to remove oxygen dissolved in water, reducing the oxygen concentration to less than one billionth. The reason for such a low oxygen concentration in semiconductor production is that high oxygen concentrations reduce the yield of contacts. Today, membrane contactors have become standard components for the removal of dissolved oxygen and CO2 from water, and are widely used in high-purity water production and industrial processes. Large-scale membrane contactors have a larger membrane surface area, and as flow rates increase and gas emission standards become stricter, using membrane contactors becomes more cost-effective. Ultra-pure water systems can also provide pollution-free water, which can be used as water for injection, in steam systems for supercritical coal-fired boilers, and for cleaning chips in the semiconductor industry. Additionally, the Christ water treatment system offers such water treatment membrane technology. Membrane filtration technology and ultra-pure water production: Membrane separation technology can also be used to produce ultra-pure water, such as water for boilers. WAT-membratec can provide such technology as well as a range of services, including advice on initial design and planning, preliminary research, planning, production, automation, and commissioning, up to routine equipment maintenance carried out by the company’s highly qualified staff. A membrane contactor is installed between the reverse osmosis unit and the electrodeionization unit to remove CO2, while also removing the O2 dissolved in water to keep its concentration below 0.02 mg/L. Therefore, the same pure water system can be used in semiconductor production and dialysis stations. According to McIlvaine’s latest projections, the market for world ultra-pure water production systems will reach $4 billion by 2009. Among them, the industry that uses the most ultra-pure water is the semiconductor industry, whose market value was expected to exceed $1.7 billion by 2009. The growth of the market mainly comes from Japan, South Korea, and China. McIlvaine expects the demand for ultra-pure water production systems in the pharmaceutical industry to grow at a rate of 8% per year, with the market value reaching $300 million by 2009. In the biotechnology sector, the demand for ultra-pure water systems is much higher than that in the entire pharmaceutical industry. At the same time, in the power industry, the demand for ultra-pure water systems in coal-fired power generation boilers is also growing rapidly. The latest supercritical coal-fired boilers have very high efficiency, while greenhouse gas emissions are also significantly reduced. Due to the very high pressure and temperature of such boilers, the purity requirements for water are much higher than those for subcritical boilers. According to McIlvaine’s projections, by 2009 the market demand for ultra-pure water systems in coal-fired boilers will exceed $1 billion. In comparison, the cost of ultra-pure water used for steam turbines is only $50 million. Recently, GE has introduced a new type of filter membrane material that can withstand a pH range of 2 to 12, whereas traditional membrane materials can only tolerate a pH range of 4 to 10 ； At the same time, GE has also introduced filter membranes that can operate at 90°C to regenerate heat condensates at higher temperatures; this eliminates the need to reheat water in boilers or other processes, thereby saving energy as well. The temperature that a standard filter membrane can withstand is only 60°C. The USFilter module from Siemens Water Treatment offers a membrane bioreactor called MemJet MBR Express. This reactor combines activated sludge with microfiltration membranes; it has an inlet for wastewater at its front end, and a set of hollow fiber membranes at its outlet end. As the wastewater flows through the reactor, air is injected to enhance the activity of the biological reactions. The introduction of air serves two purposes: one is to prevent contamination of the filter membrane, and the other is to increase the oxygen concentration inside the reactor. The solids trapped by the filter membrane return to the inlet of the reactor for reuse, thereby ensuring that the solid content concentration remains at 10,000–15,000 mg/L. In contrast, in traditional activated sludge treatment processes, the solid content concentration is only 3,000–5,000 mg/L. Due to the higher concentration of solids, the bacterial treatment efficiency is also higher. Traditionally, most new treatment facilities were first installed in municipal water treatment plants, but recently some water treatment facilities have also been set up in oil refineries, petrochemical plants, and steel mills, resulting in a gradual shift in the focus of where wastewater treatment facilities are installed. (end)