By Peter Chawaga, Associate Editor, Water Online
Industrial operations are always looking for cheaper, easier ways to access water. It is one increasingly scarce resource that production across the board requires regularly, from power generation to food and beverage manufacturing.
There is one common water source, however, that many may not have considered utilizing. As the summer months approach, more operations will be turning to their heating, ventilation, and air conditioning (HVAC) systems, and will want to put their condensate to good use.
To produce cold air, HVAC passes it over a cooling coil. As the temperature of the air drops, its capacity for holding moisture is reduced. When the moisture condenses out of the cooling coil, it is collected in a pan and, typically, drained away. With condensate harvesting systems, however, it can be collected for reuse.
“The water recovered from condensate harvesting is generally clean and ready to use in many commercial or industrial applications,” said Erik Knezevich, the president of Galaxy Consulting Engineers, who helped Rice University recover its HVAC condensate.
This is a particularly appealing source of water reuse, as many operations must run HVAC systems anyway and the water they produce is sufficient and needed for several applications.
“As for the use of this water, it is pure and essentially the same as dematerialized water, with essentially no minerals present,” said Paul Puckorius, president and CEO of Puckorius & Associates Inc., a water treatment consulting firm. “It can be used in cooling towers, as boiler feed water, flushing toilets, and irrigation. With a little treatment to eliminate bacteria, it could be used as potable water.”
Of course, the condensate harvesting practice is particularly well suited for operations in humid climates that condition a lot of air.
“The amount of condensate produced in Denver, CO, even in a large HVAC system, may be very little since the air humidity is very low, while a much smaller HVAC system in Houston, TX, will produce a considerable amount of condensate, since the air is high in humidity or moisture,” Puckorius said. “It depends on the humidity or moisture in the air passing over the coils and the size of the coils in the air-handling units.”
Of all its potential applications, HVAC condensate harvesting to meet cooling tower needs provides a basic look at how to apply the water source.
“Cooling towers are always a good use. You are constantly having to make up water in a cooling tower,” said Knezevich. “In order to use the condensate in a cooling tower, it is a simple matter of getting the water to the tower.”
While that may be a relatively simple matter, it is likely an operation will need to pump the water up to the cooling tower at an expense. Biological growth control like the use of chlorine is also probably necessary, but Knezevich pointed out that most cooling towers already rely on such measures. It should be noted, also, that condensate water may be too clean for use in a cooling tower.
“Condensate is actually pure water, so it is too good for cooling tower makeup, but if mixed with water containing some minerals, it is often [used that way],” said Puckorius. “Blending of condensate with city water to provide water that is acceptable for cooling towers would be great.”
These inconveniences may cut into the actual cost savings that operations realize for reusing their condensate water.
“Cost savings must take into account the savings in most water and sewer charges, as well as any energy costs that will be incurred pumping water from the HVAC system to its point of use,” Knezevich said. “The more complex of a system that is required, the lower the ROI. Warm and humid climates will likely benefit more from this technology than cooler, drier climates. Large systems can also gain greater savings from their economies of scale.”
As always, however, finances aren’t the only consideration for industrial reuse ventures.
“Clean drinking water is a vital resource,” said Knezevich. “We hear in the news of different parts of the nation going through severe droughts, falling levels in the nation’s aquifers, and pollution of surface water. The use of condensate harvesting means we are offsetting a portion of the demand for this vital resource.”
Image credit: "HVAC Mechanical Services Dubai, Multitech© 2011 used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by-sa/2.0/