A thirst for clean water

C&I Issue 2, 2009

Around €3 trillion – or €150bn annually – is required to meet the world’s needs for water infrastructure over the next 20 years, according to estimates by the Global Water Partnership, an alliance of public and private organisations in water management. The biggest driver behind the demand for water treatment technologies and systems – most of them chemical based – will be water scarcity. By 2025 nearly half of the world’s population or around 3.5bn people will be living in areas of water stress, according to the World Resources Institutes.

Before the onset of the recession, US market research organisation The McIlvaine Company was forecasting 5% average annual growth in global sales of water and wastewater chemicals between 2008 and 2012. But some sections of the market, like chemicals serving filtration and membrane facilities, will expand much faster. The world market for large-scale reverse osmosis (RO) membrane systems, for example, is expected to increase by almost 50% in the next four years. In the desalination segment, Oxford, UK-based Global Water Intelligence is predicting RO will overtake rival evaporation and distillation technologies in terms of market share.

Much of the massive rise in investment over the next several years will be in engineering systems that will need the support of chemical solutions to treat water effectively. They will also require the development of new materials, particularly polymers. The biggest need will be in regions with fast growing economies, such as Asia, where the water treatment market is reported to be growing at 8% annually.

‘The percentage of people with access to adequate safe drinking water within 1km of their homes remains woefully inadequate in areas with the greatest potential and expectations for rapid economic development,’ says Erik Fyrwald, chairman, president and chief executive of Nalco Company in Illinois, US, a global supplier of water chemicals and integrated treatment services.

Industrial growth can be a major source of increased water consumption, as well as pollution. At the same time, industry has big opportunities to be more efficient in the use of water. ‘Economic development will need to coincide with improved access to safe water for domestic use,’ says Fyrwald. ‘Through using less water and fully treating discharged water, [industry] must contribute to meeting this basis human need.’

Among the world’s numerous industrial water treatment facilities, and an estimated 150,000- 200,000 water and wastewater utilities, there will be continued robust demand for traditional chemicals, like aluminium, iron and polymer based coagulants and flocculants and long established disinfectant treatments, such as chlorine gas. However, there is likely also to be a swing away from conventional chemicals to more sophisticated, specialty products for removing specific organisms and contaminants.

The trend towards integrated treatment systems means that chemical companies serving the water sector are diversifying into areas like water treatment equipment, consulting and engineering, maintenance services and monitoring and testing. They are using their expertise in chemistry not just for the development of treatment chemicals but also new materials for improvements in equipment.

Through its knowledge of polymers, for example, Dow Chemical has built up its FilmTec operation into a leading supplier of membranes for filtration and reverse osmosis systems. And at Nalco, in addition to supplying a comprehensive range of treatment chemicals – in particular polymers to control microbial growth, mineral deposits and corrosion – the firm is a major provider of monitoring and testing systems. Nalco was one of the first companies to develop a realtime, on-line monitoring system, called Trasar, which uses fluorescent measuring techniques to ensure the application of precise concentrations and dosages of chemicals.

In the expanding membrane filtration sector, there is intensifying competition between the major membrane suppliers led by Dow, California-based Hydranautics, owned by Nitto Denko of Japan, and the Japanese-based Toray and Toyobo, to develop polymer compounds that drive down the cost of the RO process in desalination.

RO desalination is now a major source of water in the coastal areas of water-scarce countries around the world. In Perth, Australia, 17% of the city’s water needs are provided by a single 250,000 m3/day RO desalination plant. Algeria is planning to construct 13 RO desalination plants within the next three years. China has also launched a major desalination programme to provide water for industrial projects in its eastern coastal regions.

However, the demand for RO desalination technology could expand even more quickly if its relatively high operations costs, mainly due to high energy use, could be reduced. Currently, Singapore’s Tuas RO desalination plant, with a capacity of 136,000m3 water/day, is considered to have the lowest running costs at $0.48/m3. Most other RO desalination plants average around $1/m3.

To bring down operating costs, membrane suppliers are improving the performance of their polymers to reduce the pressure within the RO system and so lower energy consumption. In reverse osmosis, water is pushed through the polymer matrix whose dense layers prevent the passage of the salt. The polymers mainly comprise compounds based on cellulose acetate, polyamide and polysulphone. In addition, the polymers are often coated with substances to counteract fouling and corrosion.

The objective of the membrane producers has been to make their polymer sheets as thin as possible so that more sheets can be fitted into each membrane element to maximise the active area without sacrificing durability and consistency. At the same time, the flow rate has to be increased and the pressure decreased.

FilmTec, for example, has introduced elements with flow rates of 9000 gallons/day and a salt rejection rate of 99.7%. This compares with FlimTec’s flow rates of 4000 gpd and salt rejection levels of 99.4% in the early 1990s. At that time a typical desalination plant operated at a feed pressure of 70 bar. In FilmTec’s latest field tests with new RO technologies the pressure can be reduced to as low as 4.5 bar. These advances should help to cut running costs to at least $0.24/m3, half that being reached at Singapore’s Tuas facility.

To perform properly, RO systems require feed water free of a range of contaminants, in particular suspended solids, colloidal material, bacteria and scale deposits Nor does RO eliminate all pollutants, despite being relatively efficient at eliminating microorganisms.

As a result, RO facilities require pre- and posttreatment facilities, often comprising other filtration methods, ion exchange systems using resins, electrodeionisation (EDI) and activated carbon, as well as the application of conventional chemicals.

Different polymers in the RO systems will have different pre-treatment needs. Some RO polymers, for example, are damaged by chlorine so that chlorine used in the early stages of pre-treatment then has to be removed. Polyamide is susceptible to fouling and is incompatible with oxidants.

In all water treatment systems, the final stages of the process are becoming increasingly important, particularly in developed countries where stricter regulations are curbing the discharge of microorganisms and specific organic substances. The recently approved Water Framework Directive (WFD) in the European Union will force European consumers and industries to be more efficient in their use of water and to reduce emissions of previously tolerated pollutants.

Also, industries like semiconductors, pharmaceuticals and electricity generation, particularly nuclear power, are requiring the supply of ultrapure water (UPW). An 8-inch silicon wafer for making 100 semiconductor chips requires 2000 gallons of UPW to reach the necessary levels of cleanliness.

Ion exchange is now being used more widely in industries because it can help to provide water meeting UPW standards. It can be far more selective in its elimination of substances than filtration or membrane systems.

Water coming out of wastewater treatment plants will need to become cleaner as countries and industries become more reliant on reused and recycled water. Singapore, for example, aims to depend on reused water for 30% of its water supplies by next year. Israel is planning to reuse around a quarter of domestic water consumption for purposes like crop irrigation.

In a recent survey of water managers, 55% said they considered purification and reuse as the most important option for meeting future increased demand for water.

‘The only way of solving the water crisis sustainably is to purify and reuse water more efficiently than today,’ says Hallvard Oedegaard, a water specialist at the Norwegian University of Science and Technology, Trondheim.

He points out that water applied in the three major uses of agriculture, industry and domestic consumption is not only a resource for recycling, but also contains components for other uses, which can help to offset treatment costs. These include nutrients like nitrogen and phosphorous. For example, Kemira, the world’s biggest producer of inorganic coagulants, recovers spent acid from wastewater treatment plants at steel plants for use in the production of its own chemicals.

Heat in water, especially in industrial processes, can also be retrieved for energy purposes. Carbon in wastewater can be a source of biofuel, while dewatered sludge has become a feedstock for anerobic digesters to make biogas.

‘Water and energy issues need to be viewed holistically in energy production and in efficient use of water and energy,’ says Nalco’s Fyrwald.

In fact, the future of water as a resource probably lies in a holistic approach that integrates utility systems, industrial processes and wastewater treatment. This will extend even further the scope for combined chemical and engineering technologies in the water sector.

Sean Milmo is a freelance writer based in Essex, UK.

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