Aqua-Pure is the premier recycler of industrial wastewater in North America.

MVR EVAPORATION

Of the various methods available to treat wastewater, nature's method – evaporation – is still the most effective. Evaporation enables pure distilled water to be recovered from feedwater that contains dissolved solids. The feedwater is boiled to produce steam, leaving behind all dissolved solid contaminants. The steam is then condensed into pure distilled water.

In order to control the level of dissolved solids in the concentrated boiling fluid, a constant stream is drawn off. This is called concentrate. All of the dissolved solid contaminants that enter the system in the feedwater leave the system in the concentrate.

For example, a feedwater stream consisting of a dissolved solid, such as sodium chloride (NaCl, or salt), will produce a distilled water stream and a stream of concentrated sodium chloride.

Aqua-Pure has taken existing evaporator technology and combined it with process innovation and state-of-the-art heat exchanger technology. The result -- Mechanical Vapor Recompression (MVR) – is the first major breakthrough in evaporator technology in over 25 years.

In MVR systems, a compressor is used to add the energy required to boil feedwater into steam. The NOMAD units operated by Aqua-Pure are MVR evaporators.

Here’s how the process works –
Feedwater enters the NOMAD, breaks into two streams and flows through the pre-heat exchangers. One feedwater stream cross-exchanges with distilled water leaving the system, as the other stream moves past the concentrate as it exits the system. Both the distilled water and concentrate streams are very hot (near boiling), and they transfer their heat to the incoming feedwater. The two feedwater streams never re-combine.

Next, the hot feedwater passes through a de-aerator, in which dissolved gases (such as carbon dioxide) in the feedwater are released and vented. The hot de-aerated feedwater then enters the recirculation loop.

The recirculation loop consists of boiling concentrate flowing from the separator to the circulation pump to the evaporator exchanger and back to the separator. The circulation pumps transfer the concentrate from the separator up through the evaporator exchanger, where some of the concentrate is boiled into steam. A mixture of steam and boiling concentrate exits the top of the evaporator exchanger and flows into the separator.

Inside the separator, the steam is separated from the concentrate. The steam is drawn from the separator by the compressor, which adds pressure to the steam, causing its temperature to rise. This high-temperature, high-pressure steam is driven back down through the evaporator exchanger, where it condenses into distilled water and passes its heat to the boiling concentrate, producing more steam.

Hot distilled water flows from the bottom of the evaporator exchanger and into the distillate receiver. It is then pumped through the feed/distillate pre-heat exchanger, where it cools down by passing its heat to the incoming feedwater. The cooled distillate water then exits the system and flows into the distillate pit.

To prevent the salt concentration from getting too high in the recirculation loop, a constant stream of boiling concentrate is drawn from the separator with the concentrate pump. The boiling concentrate is pumped through the feed/concentrate pre-heat exchanger, where it, too, cools down by passing heat to the incoming feedwater. The cooled concentrate then exits the system and flows into the concentrate storage tanks.

This MVR process is highly complex, yet extremely efficient. Whereas boiling water on the stove requires 1,000 BTU of energy to produce a single pound of steam, MVR evaporation uses a theoretical 50 BTU of energy to produce the same pound of steam (or 5% of the energy of conventional evaporation).