WET News

20 WET NEWS november 2015 T he world's water resources are under growing pressure both in terms of quality and quantity, as population rise is giving demand to a global increase in the need for fresh water, and quality is being compromised by escalating pollution on ground and surface waters. Hazards to water resources are not solely confined to drinking. Contaminated water can pose environmental threats to ecosystems and lead to waterborne diseases. Some waters, polluted by nutrients, can also be a breeding ground for weeds and algae, which diminishes the dissolved oxygen levels in water, and creates a toxic environment for aquatic life. Though the picture may look bleak, there are innovative technologies available to turn what seems like a highly challenging task into an increased clean resource for both human and aquatic life. These solutions are vital for both industrialised and developing countries. Linde Gases has been successfully contributing to maintaining the quality of water treatment by developing well-proven processes. Among the most commonly used applications are the removal of water contaminants with oxygen and the adjustment water chemistry, such as scale control with CO2. Weeds and algae diminishes dissolved oxygen levels in water. Is the use of oxygen the answer? The challenge: Cleaning the world's water THE CONCEPT • SoLvoX-D is specially designed for the injection of oxygen into pressurised pipelines • oxygen is dissolved in a pressure vessel for oxygenation to be carried out • The assembly nozzle can easily be dismantled and cleaned without having to interrupt operations NEED TO KNOW 1 raw waters can contain dissolved iron and manganese as well as ammonium ions and other reduced chemical species 2 Three oxygenation plants are operating on the Canning river and two on the Swan river 3 Toxic blue-green phytoplankton blooms in concentrations exceeding guidelines set down by the World Health organisation (WHo) for recreational exposure, can pose a direct threat THE VERDICT "In its first few months of operation, the project has been a success which the project team is looking to duplicate the systems design in one of the existing oxygenation plants on the Canning river" INSIGHT WaTer quaLITy & monITorIng SoLvoX C is a pressure dissolver cone designed to increase the concentration of oxygen in water L inde's SOLVOX technology has been proven in a pro- ject in Australia on the Swan Canning river system, as oxygenation has been adopted as a primary remediation tech- nique by the government of Western Australia. The Swan estuary is domi- nated by fresh water flowing downstream in winter and salt water moving upstream in sum- mer through tidal movement as fresh water flow subsides. Rainfall runoff and stormwa- ter flow into the estuary, carry- ing with it sediment and organic matter that drives oxygen reduction within the water column. The aim of the project is to modify river conditions by maintaining dissolved oxygen levels, reducing nutrient release, preventing algal blooms and providing a refuge for aquatic fauna in an area prone to low oxygen conditions. The Swan River is in central Perth, passing through a subur- ban setting and near walkways and parks in an area used for water sports and recreation. Potentially toxic blue-green phytoplankton blooms in con- centrations exceeding guide- lines set down by the World Health Organisation (WHO) for recreational exposure, can pose a direct threat to the water, depth, tidal movements, as well as varying salinity levels and temperatures. In late 2013, the project leaders decided to extend the distribution system in the Canning River by 2.2km. Linde had worked with the Swan River Trust and Depart- ment of Water on oxygenation solutions in the past and was the natural choice for the part- nership to provide in-river oxygenation as it could deliver hydraulics to distribute oxygen- ation over a vast distance through its SOLVOX technology. Currently, there are three oxygenation plants operating on the Canning River and two on the Swan River. The most recent system designed and installed by Linde in collabora- tion with Swan River Trust and Department of Water was the Nicholson Road Bridge oxygen- ation plant on the Canning. Pro- cess design objectives sought to design a capacity for oxygen dissolution at 5-10kg O2/hr with maintenance of river dissolved oxygen concentrations above 4.0mg/l through the water column. The plant is to operate both automatically and remotely in both fresh and partially saline water conditions with a mini- mum operating life of 20 years. Finalised earlier this year, Linde provided technology for the plant that included detailed hydraulic design for equally distributing oxygenated water across 2.3km of the nominated river area. This included supplying: • A liquid oxygen storage vessel and ambient vaporisers • SOLVOX-C110 technology and pump • Oxygen control panel • A motor control panel includ- ing PLC, HDMI and remote operations The oxygen dissolution design of SOLVOX-C was to achieve complete dissolution of gaseous oxygen using a cone dissolver, unique to SOLVOX-C110. The design methodology requires that the pressure throughout the distribution pipeline is held at a required pressure in excess of the satura- tion pressure at the maximum rate of dissolution. In this case, the head-loss objective is to ensure minimal loss from the distribution "T" junction a¡er exiting the dissolver. In its first few months of operation, the project has been a success which the project team is looking to duplicate the systems design in one of the existing oxygenation plants on the Canning River. Raw waters can o¡en contain high concentrations of dissolved iron and manganese as well as ammonium ions and other reduced chemical species. Iron and manganese are detrimental to water supply as they can lead to corrosion. Following the enrichment of raw water with oxygen, heavy metal ions are removed by filtration. Linde has developed its SOLVOX systems for the efficient introduction of oxygen into the treatment of drinking water. Depending on the process application used in the modern water treatment plant, oxygen is fed directly into a raw water feed upstream of a filtration system or into a sidestream, which is then introduced back into the main flow. SOLVOX-D is specially designed for the injection of oxygen into pressurised pipelines, where oxygen is fed directly into a raw water stream through a stainless steel distribution nozzle, o¡en in combination with the installation of a static mixer downstream to ensure complete mixing. This arrangement provides a low-maintenance approach to oxygen application and the assembly nozzle can easily be dismantled and cleaned without having to interrupt operations. In the SOLVOX-R process, oxygen is dissolved in a pressure vessel for oxygenation to be carried out in an inline or people recreating and the ecological area as a whole. The oxygenation programme has been operational in the Swan Canning river system for years. Over the past 17 years, there have been multiple oxygenation trials in a bid to improve water quality and habitat conditions within the system. The trials have been shown to be so suc- cessful that ongoing oxygena- tion is seen to be a viable man- agement strategy to improve water quality and maintain a healthy ecosystem. The project has been pre- sented with a number of chal- lenges, including shallow water In australia, ongoing oxygenation is seen as the best strategy for improving water quality. A solution: Oxygenation plants prove viable The urban environment has contributed to a rise in nutrient loads bypass operation. This allows for maximum oxygen utilisation and a very high achievable concentration of oxygen.

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