Saving water with vapour condensate - for an optimised water footprint

Vapour condensate is a growing challenge for many dairies. In many countries, the liquid that is left over during the production of milk powder, for example, should really be discharged into a sewage treatment plant – after all, it contains milk constituents. “That causes work and costs, and is therefore a growing problem for dairies,” says Klaus Dickhoff, Head of Project Planning & Sales at EnviroChemie, “because the demand for milk powder is rising worldwide.” A large number of dairies have therefore been increasing their production for years. At the same time, however, they have a high demand for water, such as for example for cooling water or cleaning water. So on the one hand, they pay for the disposal of a water containing the product, and on the other hand they need water. “When you consider that milk consists of around 86 percent water, it really makes sense to use this water instead of disposing of it,” says Dickhoff.

“It takes an elaborate interaction”

Improving their water footprint was the goal with which a large dairy approached Enviro-Chemie in 2017. The dairy had already tried to treat its own vapour condensate. “It was then that they realised that it's not that easy,” says Tibor Kretschmann, project manager at EnviroChemie: “It takes an elaborate interaction of biological and chemical-physical processes.” In other words, A great deal of water treatment expertise is required to actually be able to turn vapour condensate into process water. EnviroChemie was awarded the contract for the project and started to build a larger pilot plant. “That was something new for us in those dimensions, too,” admits Dickhoff. After all, it’s not just a question of complying with certain hygiene regulations; the system should also be as easy to operate and clean as possible and function automatically. “Thanks to our know-how, we managed to achieve this,” says Dickhoff. 

The experts at EnviroChemie combined their experience from various areas of wastewater treatment. And the result, the Envopur® Re-Vap plant, a multi-stage system, is an innovation in many respects, because it combines EnviroChemie’s Biomar® biological treatment process with the Envopur® membrane process. The pilot plant was followed by a larger plant. In the near future, the dairy will be able to recycle 120 cubic metres of vapour condensate per hour. “That is an impressive figure, because it also proves that the process works on different scales,” says Dickhoff. “That makes it easy to transfer to other dairies.”

Tighter restrictions increase the pressure

Many dairies today are asking themselves what is the most efficient way of disposing of the vapour condensate. In the past it was possible to discharge the vapour condensate, and in some countries to actually use it directly in the processes, but this led to unpleasant odours and deposits. Tighter restrictions worldwide have increased the pressure here. In addition, the shortage of water is becoming an increasingly important factor for the industry. “Some dairies were built 30 years ago, and the water pipeline from back then is far too small for present-day expansion plans,” says Dickhoff, explaining the situation. Added to this are problems for dairies in regions where water is generally scarcer. “In the past, water was cheap and more than sufficiently available in many regions,” says Dickhoff. Climatic changes on the one hand and large increases in production on the other have changed this for many dairies, and dry summers are increasing in numerous countries.

The outstanding feature of the Envopur® ReVap solution is the combination of several processes: In a first step, substances are bio-degraded and filtered out in a biofilter, before microorganisms and residual turbidity are removed by ultrafiltration. In a further step, salts and ultimately organic substances are removed by reverse osmosis. “Furthermore, depending on the local requirements, additional disinfection stages with UV radiation or chlorine dioxide are possible,” adds Kretschmann. He is proud of the over 80 percent efficiency and yield achieved in the process, which in turn reduces the resulting wastewater to between 15 and 20 percent.

Using water in a variety of ways

“Treatment of the vapour condensate can already make sense from 25 cubic metres per hour,” explains Dickhoff. If dairies have to pay particularly high prices for fresh water or wastewater, the process can sometimes even pay for itself at 10 cubic metres per hour. Particularly in dairies, it is not uncommon for the wastewater plants to already be overloaded because they too were originally designed for quite different capacities. The regulations, too, have also become stricter almost everywhere. “Anyone who is already faced with the question of whether they have to invest should definitely think about treating their vapour condensate.

The dairies can then use the recovered water in a variety of ways: As rinsing water, as cooling tower make-up water or as boiler feed water. “Although treated vapour condensate is not drinking water,” explains Dickhoff, “it can have all the necessary properties for which drinking water is otherwise used in the process.” After the installation of such a treatment plant, the costs are therefore around EUR 0.75 per cubic metre of water, including depreciation and operating costs. The membrane technology employed makes the water germ-free, the reverse osmosis makes it particularly low in salt. Furthermore, it can be stored. “And with the right plant technology, it can be used to produce process water that meets the EU drinking water directive,” adds Kretschmann. It also reduces the load on the company's own wastewater treatment plant.

Saving space and energy

A further advantage: The plant is compact. “Space is another issue that customers always face,” emphasises Dickhoff. Although it consists of several stages, it can be installed in tighter spaces without any problems. Furthermore, it saves energy because it operates with numerous biological cleaning processes. “System variants that pump the liquid directly into the reverse osmosis unit are much heavier and complex by comparison,” explains Dickhoff.

Dickhoff firmly believes that the topic will become even more relevant in the future. The issues surrounding possible shortages of drinking water are more likely to increase than decrease. As a result, the costs for process water could also rise further. Waste reduction and energy recovery will continue to be issues: “Saving water also means saving CO2 – and everyone is working to reduce their CO2 footprint today.

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