Water & Wastewater
Valves in desalination
Valves in water service are often used in conjunction with pumps . Whereas pumps generate flow , valves control that flow . The most demanding applications for valves and pumps occur in desalination . Both must be resistant to the most aggressive saline media , so duplex and superduplex grades are often used on pump impellers . Apart from corrosion , criteria of selection include resistance to fast flow and cavitation , ease of inspection and maintenance , and the ability to service the valves in-line to reduce downtime . Although carbon steel , coppernickel and nickel aluminium bronze are often used on valves , stainless steel is preferred for the brine discharge process in RO desalination plants .
happens in the world ’ s driest regions , notably Israel , which recycles 90 % of its water . Now Spain and France are following suit . Veolia is currently installing wastewater recycling units at all its sewage treatment plants in France . Its Jourdain recycling project will soon secure supplies of drinking water for the Vendée ’ s inhabitants . In Milan , Rotork actuators have been installed on jet valves at a plant that recycles wastewater for irrigation . These actuators control the air inlet in the oxidation tanks , regulating the air flow that supports micro-organisms . Recycling also works within buildings : by collecting rainwater and recycling wastewater in a closed circuit , waste can be greatly reduced . Such closed loops are being installed in a Nestlé factory in Mexico and the Pearl gas-to-liquid complex operated by Shell in Qatar .
Desalination units . Photo : dreamstime .
2 . Economies and maintenance Throughout the world , an alarming amount of water is lost each day because of leaks . Corrosion-resistant stainless steel and leak-free valves are essential in the battle against this waste . But it is not only water that needs to be saved . Water management is energy-intense , mainly because of the pumps required . Compression exchangers can save a great deal of energy by recovering heat from brine in seawater RO desalination facilities . Cumwhinton , near Carlisle in the UK , is the first treatment plant to install UV LED reactors to reduce energy costs . Water companies are harnessing solar power and other renewable energy types to run their plants . Veolia and TotalEnergies have partnered to build a large solarpower system for a desalination plant in Oman .
Correct valves operation is also crucial in reducing water loss . Denmark ’ s Strømmen Water Utility installed VIDI positioners on eight strategic valves to allow instantaneous information on valve position and operation .
3 . Wastewater treatment Over the world , urbanization and increasing population are driving wastewater treatment projects . Even in the UK , despite the negative news about sewage discharges ( see box ), a number of upgrades of sewage plants have recently been carried out . At Bicester a predicted increase in population induced Thames Water to build an activated sludge plant and filter beds . At Burnley the wastewater works has been refurbished , including a detention tank and pumps , primary settlement tank , activated sludge plant , power upgrade and more .
Wastewater storage tanks .
Water and energy
Apart from being essential to sustain life , water can be harnessed to produce energy . Hydro power is the most obvious example of this , but there are others . As part of the renovations to the Afsluitdijk flood barrier in the Netherlands , a system is being installed that can generate electricity through the convergence of saltwater and freshwater ( osmotic power ). Scientists are also researching ways of harnessing the kinetic energy of raindrops to produce electricity . This can be tapped using certain materials with piezoelectric properties ( that generate electricity in response to applied mechanical stress ). π www . valve-world . net Valve World November 2022
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