A way for filtration to clean up its act
Steve Cupples gives the lowdown on a filtration system that, he says, will extend membrane lifespan and, because it uses less chemicals in the process, is kinder to the environment.With the need to be more cost efficient, and global warming now a real threat, many companies are looking at ways to enhance their performance and green image. But many firms are finding it difficult to actually reduce their carbon footprint.
Being able to reuse process water or municipal wastewater - or being able to draw on alternative water sources, such as borehole and rainwater harvesting - will go a long way to providing a sustainable solution.
On the one hand, there are a number of strategies to help make sustainability happen. On the other hand, there are factors holding things back. For example, for years it has been believed the filtration of heating or cooling water in open or closed systems is not such a big issue. Not true - there is a build up of contamination.
Big energy gains of up to 30% can be achieved by cleaning up dirty process water from heating or cooling applications.
Most industrial and commercial water sources tested show an expected contamination of more than 20µm. The distribution and population of particulates is consistently higher at less than 20µm, much of which is biological.
Significantly, this is even more pronounced below 10µm, which is the traditional cut-off point for mainstream filtration technologies. And is the key reason why a business can lose this 30% in energy performance on heating, ventilating and air-conditioning systems.
As a further example, for industry to have the ability to reuse process water for secondary, or even primary applications, will go a long way to help reduce a global reliance on valuable potable water resources. Such a strategy can give a significant return on investment.
There has not been a reliable method of filtering out fine contamination to make such a strategy workable - until now.
Self-cleaning filtration technology is set to provide a solution, because it will remove contamination to less than 1µm, without the high costs of water-polishing applications.
The CrossFlowMF1.0 has been developed to filter below 1µm - even achieving down to 0.45µm - to produce cleaner process water.
The reuse of process water just once can reduce the carbon footprint on potable water by 50%.
It is not only direct energy costs that will be affected, but also secondary costs - including:
- The ability to produce and distribute potable water for non-potable application
- A reduction in the use of water- treatment chemicals
- A reduction in electricity bills, by improving heating and cooling system efficiency
This gives lower pressure drops, longer filtration and shorter backwash cycles, making direct savings on operational costs.
The high interstitial void volume of the media allows for greater dirt- holding capacity and contamination interaction for the Zeta potential of the media to remove the finer particulates down to 0.45µm.
Compared with conventional media filtration, the inlet configuration allows for high flow-rates, these being five times higher than the normal accepted flux rates of conventional filters. Backwash volume used is also significantly lower, especially when the longer operational period is taken into consideration. It is also more effective with backwash times per unit - as low as two minutes.
This technology has been shown to provide a removal rate of more than 86% at 1µm in a single pass. Conventional filters have to do multiple passes to get close to this efficiency. So, by reducing the load on the filter in this way, you are increasing the cycle between cleaning and reducing the times the process has to stop for the membranes to be cleaned.
The need for chemical filtration is reduced. It also solves the problem of bacteria build-up associated with sand filtration.
In Australia, government departments are testing this technology to pre-filter tertiary sewage for reprocessing back to drinking water. Here in the UK, the effects on industry could be huge. For example, in their bid to meet quality standards set by major supermarket chains, food-growers are using mains water for crop spraying, which is expensive and environmentally not sound practice. The filter system means mains water can be reprocessed, by cleaning it, to meet these quality standards - and reused again and again.
Corporations will be able to reap the benefits. The life of a membrane filtration system could be extended considerably, this being anything from 20-30%. There will be less backwashing, less chemical use and longer membrane lifespan.
Most importantly, for a relatively small cost there will be improvements in efficiency and a reduction of environmental impact.
Steve Cupples is managing director of Industrial Purifications Systems.
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