Increasingly strict regulations covering wastewater discharge have prompted water-intensive industries like the food and beverage sector, pharmaceuticals, manufacturing, electronics, photovoltaics, and chemical production to explore new approaches.
To help meet their regulatory and operational goals, more and more industrial plants are investing in advanced wastewater treatment technologies. One of the advanced wastewater treatment technologies being considered is high-efficiency evaporation, such as the EVALED™ product line being offered by Veolia Water Technologies. This technology is very effective in significantly reducing wastewater volumes and helping facilities make significant progress in their “ZLD” (zero liquid discharge) strategy.
Facilities have more to gain than reduced operational costs. ZLD or reduced liquid discharge initiatives can be a core component in helping companies achieve both their corporate and UN sustainability goals as well as improving their own brand image.
Transforming Waste Streams into Resources
With water-intensive industries expected to do more with less, many are turning to evaporation and its ability to separate wastewater into two streams, a concentrate and a distillate. The concentrated solution is normally 5-10 percent of the total volume. This fraction can be disposed of, sent for further treatment, or become a source for the site to recover by-products. Meanwhile, the distillate can be reused as makeup water for production processes or utility equipment such as boilers or cooling towers.
Understanding the Science Behind Advanced Evaporation
Though it takes thermal energy for water to change phases from liquid to gaseous state, advanced evaporation technologies are able to achieve this more cost-effectively, at much lower temperatures than atmospheric evaporation.
By reducing the pressure within an evaporation process chamber, boiling and evaporation can occur at much lower temperatures. This makes the process ideally suited to use the low-grade waste heat that is available as part of many industrial processes, for example. Even where electrical or thermal energy is required, vacuum evaporation makes the process very energy efficient but still delivers high concentration ratios and effective separation for multiple kinds of industrial and process water treatments.
Industrial vacuum evaporators are a good solution in applications featuring difficult to treat wastewater in production processes such as in food and beverage or in hazardous wastewater streams in the manufacturing, pharmaceutical, cosmetics, chemicals, and manufacturing industries.
How Do the Various Types of EVALED Evaporator Work?
There are several different approaches to an effective vacuum evaporation process. These include: Heat pump-based systems, hot/cold systems, and mechanical vapor recompression systems.
Heat pump-based systems generate hard vacuums which minimize the boiling point of the effluent being treated and use electricity to run the unit. Heat pump evaporators are therefore ideal for applications in which operators are aiming to recover a temperature-sensitive product, such as active pharmaceutical ingredients.
Similarly, hot/cold systems are particularly suitable for applications that feature a low-grade heat source. If there are higher flow rates, additional thermal sources can be used, such as energy from a combined heat and power system. By harvesting this “free” energy from elsewhere in the plant, these systems can reach the same performance as heat-pump systems.
Meanwhile, mechanical vapor recompression evaporators are the most energy-efficient evaporator. Heat exchange occurs within an external shell and tube exchanger where the hot vapor coming from the compressor increases circulating wastewater temperature. Subsequently, in the boiling chamber, boiling wastewater produces new vapor that is compressed by the compressor before flowing to the shell side of the heat exchanger. This particular configuration is designed to minimize power consumption.
Capturing the Benefits of Advanced Evaporation
From very small volumes right up to hundreds of tons per day, vacuum evaporation is an effective treatment option for a wide range of low or zero liquid discharge applications which generate difficult to treat or complex effluents.
The use of efficient heat transfer technology means vacuum evaporators achieve excellent separation of wastewater to produce a high-purity distillate and achieve water recovery of more than 90 percent. This recovered water can be reused in many plant processes such as cleaning and rinsing or as demineralized boiler feed water.
At the same time, depending on the industry, the concentrate can be used to recover resources such as the sugars found in the food and beverage sector or for any number of valuable chemical compounds being used or produced in a pharmaceutical operation. This means saving on raw materials and can even create a new revenue stream. Even if resource recovery is not appropriate, advanced, high-efficiency evaporation technologies dramatically reduce waste volumes and therefore make waste disposal much more cost-effective.
As stricter regulations, environmental sensitivity, and long-term water supply concerns make industrial water use and wastewater discharges more challenging, business owners are placing growing importance on the recycling and reuse of water. While it is important to select the optimal technology to ensure an efficient process, advanced evaporator processes represent an opportunity to support businesses addressing regulatory requirements and corporate sustainability objectives and in many cases lowering the total cost of operation in their plants.