Major energy savings using pure oxygen in water treatment plants

New High Pressure nozzle injects twice as much oxygen per kWh

The advantages of pure oxygen in water treatment plants are now well known. Systems based on pure oxygen function much more efficiently and are therefore much more economical. That’s why the technology is being used increasingly in water treatment plants. Thanks to the new HP nozzle, energy consumption can be cut even further.

“Water treatment plants using ordinary outside air consume much more energy compared to plants using pure oxygen,” says Jan Mante, Application engineer at Air Liquide. "This is only logical, since outside air is 21% oxygen at most. Compressors and pumps therefore need much more energy to inject the same amount of oxygen.”

“Of course, the cost of pure oxygen has to be part of the calculation but, even then, it turns out that a lot of water treatment plants gain financially from using pure oxygen. And, of course, it might also reduce carbon footprint.”

The same, only better

“To inject and mix the oxygen into the water, we offer several Ventoxal systems. What they have in common is that they each use one or more ‘nozzles’ to actually inject the oxygen.”

“The new HP, or high pressure nozzle does exactly the same thing, but with a special twist. The story begins with pure oxygen being delivered to the site. It’s brought, as normal, under pressure in liquid form, by truck, and then pumped into a tank on site. Up to that point, nothing’s different.”

Operating principles

“Previously, the liquid oxygen evaporated into the atmosphere when it was used, losing part of the initial pressure. But we’ve been using a method recently where the gas pressure is maintained right up to the HP nozzle. That means the pressure can then be used to inject the gas into the basin. It still needs pumps, but they can now be smaller and therefore cheaper.”

“Since we reuse the kinetic energy of the gas pressure, the plant’s energy consumption decreases significantly. It reduces operating costs and carbon footprint. We used to be able to inject 6.5 kg of gas per kWh, now it's 13 kg per kWh, with the same oxygen transfer efficiency  — 85 %, for instance.”

Upgrading

“Current installations already operating on pure oxygen can be upgraded to use the HP nozzle,” explains Jan. “On the other hand, installations still using ordinary air can be converted or extended for pure oxygen. Here it’s important to know that these installations don’t necessarily have to be modified all at once.”

“For example,  water treatment plant in Hoek van Holland recently started using a system where conventional aeration combined with pure oxygen and HP nozzles. Another pioneer is Waterschap De Dommel, where nine Ventoxal oxy-injectors were commissioned with HP nozzles.”

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