Yeh talks about how a rainwater catchment system works.[Photo: Mark Wemple]
At the University of South Floridain Tampa, civil and environmental engineering professor Daniel Yeh has researched water treatment, wastewater reuse and recovery, bioenergy and desalination. But he sees many of the solutions to Florida's water woes as far simpler. Yeh, who serves on the U.S. Green Building Council's water-efficiency advisory group, talked with Florida Trend about making water a more important part of green building. Florida Trend:Many people associate green building with energy, but you point out green buildings can have an even more dramatic an impact on water. How so? Daniel Yeh:My approach has always been to first identify and pursue the low-hanging fruit. So what's the simplest thing you can do? It's harvesting rainwater. Every building should consider harvesting rainwater. Almost half of the drinking water from the municipalities goes on our grass, and we can offset that. Rainwater can irrigate landscaping and flush toilets, which is the largest water-use indoors. FT:After the toilets and the landscaping, another big water hog is cooling towers. How much water could a business save by recycling condensate back into the towers, and how hard is that to do? Yeh:After rainwater, AC condensate is the next forgotten resource. Cooling towers essentially transfer the heat from the building's air into water and then evaporate the water off to cause a cooling effect. The problem is that new, clean water is constantly needed to make up for the evaporative loss. Again, buildings often use tap water to serve as makeup water because it is available. However, both rainwater and AC condensate are extremely pure and can serve as good makeup water. The Florida Aquarium has been conserving water by feeding condensate back into its cooling towers. Another good source of makeup water is reclaimed water. To really do it right, though, I think we need to look at geothermal cooling, that is, looking at the ground, or even swimming pools, as a heat sink to cool the building air. FT:Some Florida communities seem to be taking the lead on recycling water. If you had to pick one city for best practices, which would it be?
Yeh:The city of Dunedin in Pinellas County comes to mind. They practice integrated urban water management, which means they treat all water as one precious resource, from drinking water to stormwater to reclaimed water. Most of the city's wastewater ends up as reclaimed water and is brought back to homes and businesses for irrigation. During periods of heavy reclaimed water demand, they actually go to zero discharge at the wastewater plant. Pretty amazing. Dunedin promotes water conservation not just for drinking water but also for reclaimed water. They use wireless water meters to measure water consumption on both drinking and reclaimed water lines for every customer.FT:You are part of the U.S. Green Building Council's water-efficiency advisory group that is coming up with the new set of LEED credits for 2012. What sort of changes can we expect? Yeh:The charge coming down is that 'we don't want buildings to do less bad. We want buildings to do better. To restore the urban environment.' So if you bring in air, you put it out cleaner. Same thing with water. LEED now promotes both water conservation and recycling on the building level. There will be credits dedicated to the onsite recovery of energy and nutrients embedded within wastewater. For example, we can harness renewable bioenergy stored within wastewater through technologies like anaerobic digestion. If we are clever and apply the right technologies, we can not only make wastewater treatment energy neutral, but actually create energy from waste. Innovation is driven by demand and opportunities. I think LEED will help create both.