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Water Treatment


www.chemicalsknowledgehub.com


Managing your potable water system during the pandemic


By Paul Sharpe, Kurita America


The business closures and travel restrictions mandated by the US government due to the COVID-19 virus have caused many businesses to reduce water flow in various complex building water systems. While the SARS-CoV-2 virus is not associated with building water systems, there are other pathogens and water quality issues that can potentially develop due to stagnant or reduced water flow in buildings. Paul Sharpe of Kurita America explains.


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ecause of the COVID-19 coronavirus pandemic, there may be instances in which a building’s water system needs to be shut down or placed in an isolation condition because other pathogens and water quality issues can develop due to stagnant or reduced water flow in the building. Such instances include temporary closures of the building, building renovations, or isolation of a section of a larger distribution system. A water system that is in a low-flow condition is slightly different but presents a similar potential for the development of biofilm and the amplification of potentially harmful bacteria.


Loss of disinfectant in building water systems Under normal building operation, chlorinated or chloraminated water is supplied to a building from the local municipality and the disinfectant is evenly distributed throughout the building water distribution system. However, loss of disinfectant residuals may occur due to a number of factors, including disinfectant demand, temperature, nutrient loading, and water flow. In situations described above, if the water flow stops or is significantly reduced, bacterial growth and biofilm development can increase rapidly as the disinfectant in the water is depleted. The following is an exaggerated graphic of the development process: In cases where a building’s


42 at all locations in the building.


Cross-section of potable water piping: it is important to develop a written plan to prevent biofilm formation and growth in both low- flow and idle building water systems.


water flow has been reduced (but not valved off) it is important to develop a protocol or


management plan for consistently flushing as many of the distal (away from the main header) faucets, fixtures and outlets as possible. Each of the water lines off the supply main has the potential for concentrating bacteria and biofilm. Flushing these lines will help exchange the stagnated water with fresh water containing a disinfectant. For building water systems that have been completely isolated for an extended period, a potable water disinfection (using chlorine) will be the process for any new or older piping. This will be part of the commissioning protocol and is typically mandated by the local health department prior to occupancy or human consumption. In this condition a total coliform test (positive/ negative) is performed and must be tested within 24 hours of sampling. It is best to check with local health departments for specific guidelines.


Steps to be considered


The following are some simple actions that should be considered while a building is under low-flow conditions: • Flow and exchange 3-7% of the water based on estimated total water volume for the building.


• Flow water at each distal outlet until there is a chlorine residual (free or total) based on the type of disinfectant. This will require a free or total chlorine test kit. Additionally, a specific test for monochloramine can be used for chloraminated systems.


• For hot water potable systems, the water should be flushed to the point where either the water temperature is the same as the hot water main or above 120°F (where allowed). This will require a thermometer.


Once the building water system is scheduled to return to normal service, flushing should be increased, and additional testing is advised. • Disinfectant levels should be at or near the supplied water levels


• Samples for total heterotrophic plate count should be collected and cultured. Total heterotrophic plate counts should be less than 500 colony-forming units. Local certified water testing laboratories will be able to perform these cultures and interpret the results.


One of the most effective means of reducing bacteria amplification and biofilm development is simply exchanging the old water with new. Waterborne pathogens can concentrate in stagnant water if the building distribution system is not flushing regularly. It is important to develop and follow a written plan for both low-flow and idle water systems. Documenting the process and procedures followed will help if a shutdown is required in the future. Further details, including proactive steps to minimize water stagnation during building closures and actions items to address water quality prior to reopening, are available in a recent publication from the US EPA https://www. epa.gov/coronavirus/information- maintaining-or-restoring-water- quality-buildings-low-or-no-use


For more information on how to address water treatment issues, contact Kurita America’s water treatment experts at:


Kurita America Inc Ph: +1-866-663-7633 W: www.kuritaamerica.com


Autumn 2020


www.chemicalsknowledgehub.com


Materials Science


High-performance fibres and fabrics for demanding work, sport and leisure applications


Royal DSM has developed a range of bio-based high-performance fibres and fabrics that not only provide innovative, lightweight solutions for demanding applications in the workplace and professional sporting environments, but that also provide an environmentally sustainable alternative that contributes to the circular economy.


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n line with its commitment to protect people and the environment they live in, Royal DSM introduced the world’s first-ever bio-based high- molecular-weight polyethylene (HMPE) fibre in May of this year. This bio-based version of the company’s Dyneema fibre has been designed to offer exactly the same performance as its conventional Dyneema fibre but with a carbon footprint that is 90% lower than that of generic HMPE, as it is sourced from renewable feedstocks: compared to generic HMPE fibres, this new fibre emits 29 tonnes less carbon dioxide per tonne of fibre produced.


Dyneema fibre: strength, performance, sustainability


Bio-based Dyneema is fifteen times stronger than steel at the same weight, has very high cut and abrasion resistance, and is highly resistant to chemicals and UV light. The fibre is available in a wide range of yarn thicknesses (known as titers), from 110 to 2640 dtex, making it suitable for applications ranging from fishing lines to heavy-duty applications such as tug ropes.


DSM uses a mass balance approach to track the bio-based materials through the value chain.


Through the sourcing of waste from the timber and pulp industries, bio- based feedstocks are blended with fossil feedstock to produce ethylene and a mass balance approach is used to track the amount of bio-based materials and their sustainability characteristics, enabling DSM to allocate the ‘renewable share’ to its products. DSM says this approach helps the company and its partners and customers to reduce their overall reliance on fossil fuel-based resources while supporting the environment and the circular economy.


Bio-based Dyneema fibre is International Sustainability and Carbon Certification (ISCC)certified, guaranteeing good and sustainable practices while verifying that the product originates from a transparent and traceable supply chain. The ISCC certification also guarantees that the amount of bio-based material sold is no more than the amount sourced.


Dyneema fabrics: varieties for a range of applications


DSM also produces a range of Dyneema fabrics which are available as composites, denim, knits, wovens and hybrid fabrics for composite reinforcements. These fabrics have been molecularly engineered for use in a wide range of industrial and domestic environments. The company says they make products lighter without compromising on strength and durability and that they also make products significantly stronger without compromising on comfort. Strengthwise, they are 15% stronger than steel on a weight per weight basis, they are 30% lighter than nylon and polyester and 45% lighter than aramid. The new fabrics are also UV- and water-resistant as well as abrasion- and tear-resistant. They are available in a range of product types as follows:


Autumn 2020


Dyneema Composite Fabrics are designed with greatly increased tear, puncture, and abrasion performance dramatically compared with 500D nylon, but with much lower weight and reduced bulk. They can be tailored and optimized for strength, stretch and weight at specific points or along predetermined load paths, the adaptable properties of these flexible composite fabrics allowing them to be used in a range of applications and industries from outdoor sports equipment to emergency medical products. Dyneema is also available as a denim and is available in two forms: as a filament yarn for reinforcement, or with Dyneema blended into the cotton. ‘denim with Dyneema’ has been designed to create much stronger and more durable jeans when used as a filament reinforcement. DSM says that blending it into the cotton creates a lighter, more comfortable pair of jeans that has the same strength and durability as conventional denim and that a garment’s performance can be tailored to its intended use by adjusting the amount of Dyneema fibre it contains.


Rigid and stretch woven fabrics can be made using Dyneema to create strong and lightweight outdoor apparel, footwear and accessories, while coloured materials are also possible using coloured companion fibres. Woven fabrics with Dyneema can be coated and the coating and underlying fabric tailored to meet specific customer specifications. Knitted fabrics with Dyneema are available in various circular and warp knits designed to meet the specific needs of the final application. These knitted fabrics can be easily combined with other synthetic or natural yarns while single-jersey, double-jersey, terry, and interlock knit fabrics are all possible, with or without elastomeric yarn. There are also special Raschel warp knit fabrics with Dyneema: these are available in net constructions for use in liners and athletic footwear.


with Dyneema is a strong and light hybrid of pure carbon and Dyneema fibre that is much less prone to vibration and shattering than carbon fibre on its own, enabling the engineering of composites that resist impact forces 50% to 100% better than carbon alone.


Dyneema in the Tour de France


One recent application for Dyneema fabric has been its use as the fabric of choice for Sunweb’s protective cycling jerseys worn by the team’s riders in the 2020 Tour de France. Working with Team Sunweb and Craft Sportswear, DSM helped to deliver a cycling jersey that, when combined with a protective base layer, was able to offer cyclists effective abrasion protection at speeds up to 60kph while also reducing the severity of open wounds at even higher speeds. DSM says that, in this way, the company has been underlining its commitment to protect people and the environment.


Further information


For further information on DSM’s Dyneema fibres and fabrics visit www.dsm.com/dyneema


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