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Water Treatment


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Advanced technologies for water and wastewater treatment


Ultrafiltration (UF) and reverse osmosis (RO) have been used for purifying water for many years but these two technologies continue to undergo further development to meet the requirements of new and more-demanding water treatment applications. Global industrial speciality chemicals company LANXESS is at the forefront of these developments, as demonstrated by the examples described below.


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acting as the sales partner for Polymem’s Gigamem neophilic hollow-fibre high-quality UF membranes, thus enabling LANXESS to add UF to its existing technology portfolio for water treatment.


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embrane techniques have enormous potential for water treatment. One example is the


combination of ultrafiltration (UF) and reverse osmosis (RO) to treat wastewater flows containing suspended solid matter. A good example of an RO-based process is the treatment of pig slurry, which has been successfully practiced for many years by wastewater treatment specialists in the Benelux countries. In this example, a physicochemical treatment is used in the first step, ferrous sulfate and a flocculating agent being added to the slurry. The solid matter is then separated by means of a strainer and sold in


granulate form as a natural organic garden fertilizer. The remaining liquid phase is then concentrated further using RO and, in combination with an ion exchange process, most of the ammonium ions present are removed from the permeate. Thus, this slurry treatment results in a granulate and a concentrated liquid phase that are more easily disposed of without affecting the environment and, in addition, clean water is produced, this water being easily fed into the water cycle.


Combined process for solids and borate removal


Another UF/RO water treatment example is provided by the


recent collaboration between French company Polymem SA and Germany-headquartered global industrial chemicals company LANXESS in completing a project for an Italian oil company as part of a sales partnership. In the project, a combination of UF/RO is used to remove total suspended solids (TSS) and borate from the wastewater of an oil refinery in Apulia, Italy and making it available for reuse within the process. TSS can be completely removed and borate content is reduced by about 97%. This low-pressure process requires only a relatively low investment


A single Lewabrane membrane element consists of a package with more than 20 layers. This is assembled into a spiral wound element with a diameter of 20 centimetres and a length of one metre and then fixed. (Photo courtesy of LANXESS © Thorsten Martin)


and is also very low in energy consumption. The project has been so successful that the companies are in further discussions concerning an expansion of the system. LANXESS and Polymem have been working together since mid-2018, with LANXESs


Autumn 2020


Ion exchange technology for demineralized water LANXESS is also a major technology provider for the production of demineralized water, an important industrial solvent. Untreated water can be purified with the company’s Lewatit ion exchange resins or its Lewabrane RO membrane elements or by a combination of both depending on requirements, and obviously wastewater from chemical production plants must also be treated to protect the environment. Ion exchange and membrane processes are important technologies that contribute in this area as well. Ion exchange resins are highly effective even under extreme conditions, including for the treatment of highly concentrated, hot salt solutions for chloralkali electrolysis. They can remove alkaline earth and heavy metal ions, thus protecting the membranes from contamination in eco-friendly and energy-efficient membrane processes. Mercury is still found in the brine cycle, but can be eliminated by ion exchange resins after making the conversion from a mercury cell to a membrane process. Similarly, other process solutions, such as pickling acids, rinse water or electroplating baths, can be treated. Ion


exchange resins have other


Autumn 2020 39


LANXESS and Polymem have been working together since mid-2018, with LANXESs acting as the sales partner for Polymem’s Gigamem neophilic hollow- fibre high-quality UF membranes, thus enabling LANXESS to add UF to its existing technology portfolio for water treatment.


customers to identify new, innovative applications for such polymer catalysts and developing new, customized product grades.


Process water treatment


applications within the chemical industry: they are firmly established as versatile and efficient catalysts and are used, for example, in acid-catalyzed saponification, ester and ether synthesis, and the production of biodiesel. They are also used, in combination with metal ions, in hydrogenation reactions, and LANXESS has been working with


Another recent RO project undertaken by LANXESS was the installation of a Lewabrane RO B400 FR membrane system in Egyptian fertilizer producer AlexFert’s new BWRO plant in Alexandria. This water treatment plant is fed with canal water (with the River Nile as the origin), and has a seasonally variable TDS of 300–550 mg/l. The pre-treatments for the water are coagulation, cold lime softening, and filtration, and the RO plant consists of two trains, each of 120 cubic metre per hour feed with 74% recovery. A single train is composed of two stages in a 13:6 array with six elements per vessel. These RO units were placed into an existing water treatment plant upstream of the plant’s ion exchange full


Water Treatment


demineralization trains based on Lewatit MonoPlus resins. The Lewabrane RO elements achieved salt rejection of up to 99.76% at 20°C, leading to a permeate conductivity of the order of 3 to 5 µS/cm, thus significantly reducing ionic load for the resins in the demineralization unit and resulting in a stable and reliable process. Furthermore, the new RO plant allows a reduction of specific chemical consumption of the resin bed due to less frequent regenerations.


Further information on LANXESS’s Liquid Purification Technologies business unit please visit http://lpt.lanxess.com


LANXESS produces Lewabrane membrane elements for water treatment at its Bitterfeld, Germany facility. These


membranes filter out undesirable substances from water such as salts, pesticides, herbicides, viruses, bacteria and minute particles. (Photo courtesy of LANXESS © Thorsten Martin)


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