The pressure is on!

Published:  08 July, 2011

 The pressure is on everyone to save energy and resources, both for environmental reasons and to save money. For steam users, reverse osmosis (RO) can deliver a step-change in energy efficiency and reduce their carbon footprint, says Mike Griffin, Spirax Sarco’s UK technical manager – Steam Systems Conditioning. 

 RO is a robust, chemical-free technology that uses semi-permeable membranes to deliver purified water to boilers and clean steam generators. It’s a well-proven technology that’s already widely used in industries such as water and wastewater treatment and food production. But a combination of recent technical innovations and increasing pressure to save energy and resources mean that today’s advanced and compact systems could help many steam plant users who may never have considered RO before.  

Save energy and reduce emissions

It’s a process that can deliver a range of different benefits, but the biggest driver for most steam users to invest in RO is the need to save energy and reduce costs. That need is intensifying all the time. For example, the climate change levy is essentially a tax on energy use, and businesses in energy-intensive sectors may be eligible for a reduction in the climate change levy by meeting energy reduction targets. Meanwhile the European Union emissions trading system requires organisations in energy-intensive sectors to report and meet targets to reduce CO2 emissions.

And it’s not just the biggest energy users that are coming under pressure. The Carbon Reduction Commitment (CRC) Energy Efficiency Scheme is a mandatory scheme aimed at improving energy efficiency and cutting emissions in large public and private sector organisations, including small to medium industrial facilities. These organisations are responsible for around 10% of the UK’s emissions.

Although the CRC Energy Efficiency Scheme was amended in late 2010 to reduce the burden on businesses, revenues from allowance sales totalling £1 billion a year by 2014-15 will be used to support the public finances, including spending on the environment, rather than recycled to participants. League tables will be produced and organisations will be taxed according to their emissions performance.

Inevitably, such measures will continue to ramp up the cost of energy. The Chemical Industries Association and the TUC have estimated that existing climate change mitigation schemes will double energy costs for many industries by 2020 and any new proposals will add to the burden. 

Achieve a step-change in consumption

Of course, no single technology can entirely mitigate the coming price hikes, but RO can make a significant contribution by slicing as much as 3% off the fuel bills of typical steam users.

RO is commonly used in conjunction with water softening, chemical dosing or filtration to deliver purified water to boilers and clean steam generators. By stripping out almost 99% of the dissolved solids, RO can reduce boiler blowdown by an order of magnitude, resulting in significant savings in energy, water and treatment chemicals.

RO uses a pump to force a stream of water through a semi-permeable membrane, separating it into two streams. One is the reject stream or concentrate stream and the other is the purified water or permeate stream.  The permeate typically flows to a holding tank or hot well before being set to the boiler or clean steam generator.

RO membranes do not need to be regenerated using the acid or caustic chemicals used in conventional dealkalization or demineralisation plants. This makes RO generally safer and easier to manage. 

Applicable to all

Virtually all steam users stand to benefit from RO, whether they’re tackling hard water in hospitals or fighting contamination in food factories. Used in combination with the right treatments, RO helps cut down on plant outages caused by scale and reduces corrosion in the condensate circuit.

While it’s not entirely fit-and-forget, RO is a low-maintenance technology and the use of long-life membranes and quick-fit fittings help keep the time and cost of servicing and maintenance to a minimum. In fact, the biggest running cost associated with RO is the cost of pumping the water through the treatment membranes. 

Extra savings

Conventional RO systems reject approximately one third of the water that passes through them. However, Spirax Sarco’s zero-loss system uses new technology to improve RO performance and sustainability, reducing water losses from the RO system to virtually zero.

Depending on fuel costs, this alone can save users around £10,000 per year in a 2 tonne per hour unit. This adds to the achievable savings and leads to a rapid return, with Spirax Sarco RO systems typically paying for themselves in under a year, and often as quickly as six months.

Many engineers are wary of the potential work or maintenance issues associate with introducing an unfamiliar technology, but RO combines the potential for major benefits with easy maintenance and straightforward operation. It’s time for all steam users to consider how RO could help them reduce their bills. 

What’s the right RO system for you?


  • CSM-RO units provide the ideal pre-treatment for clean steam generators, with output capacities ranging from 400 to 2000 litres per hour.
  • Standard Zero-loss RO systems are available in space-saving vertical versions for up to 1600 litres per hour output and horizontal versions for up to 50,000 litres per hour output.
  • Compact RO systems are a cost-effective option for steam generators of capacities of up to 1600 litres per hour.
  • Hot-RO systems clean up hot condensate or any other hot water up to 70oC to be recycled back to the boiler. They prevent any contaminants from building up in the steam system.
  • Bespoke RO systems can also be made to order for applications of any size.


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