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Wednesday, August 11, 2010

Water Conservation Begins at Home - Think Twice, Flush Once!

In most homes, toilets are the largest water user inside the home. Although the federal Energy Policy Act of 1992 mandated a maximum of 1.6 gallons per flush (gpf) for new toilets beginning in 1994, many homes and apartments still have older toilets that might use 3.5-gpf or more. If you’re in an older home, get rid of that old flusher fast!

High efficiency toilets (HETs) use at least 20 percent less water than standard 1.6-gpf models. The most popular household HET is the dual-flush toilet. Dual-flush toilets use about 1.6-gpf for solids and 0.8 to 1.1-gpf for liquids. For a household of four people, the savings from a dual-flush toilet is about 3,360 gallons annually, reducing water use for sanitation by 37.5 percent and total household water consumption by 10 percent.

Nearly every toilet component, including the tank, flush valve, bowl rim and trapway, has been re-engineered using tools such as Computational Fluid Dynamics (CFD) computer modeling, making today’s models far more reliable than first generation HETs from the 1990s.

In the 1970s, during times of water shortages, a popular motto was, “If it’s yellow, let it mellow; if it’s brown, flush it down,” and everyone put bricks in their toilets to save water. Now, with dual-flush toilets, we can accomplish the same goal and not disrupt the flushing mechanism.

 

Posted by Jerry on 08/11/2010 at 04:12 PM

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Monday, August 09, 2010

Time to Put Rainwater Harvesting into Every Green Building Project?

Capturing the free water falling from the sky is gaining popularity in the U.S. and in other countries as diverse as Australia and Germany. When considering rainwater harvesting, we usually think of the “active” variety. Active rainwater harvesting combines collection and storage with on-demand use and is an excellent way to supplement residential and commercial water supplies, because rainwater is soft and free of disinfectants, salts, minerals and human contaminants. The majority of rainwater captured in this manner is used for irrigation and flushing toilets. With today’s water prices, rainwater collection and reuse systems typically have medium-to long-term payoffs. However, there may be other financial benefits for commercial projects such as reduced sewage collection costs and lower water meter fees (because a project might need less municipal water.) “Passive” rainwater harvesting, on the other hand, is less expensive. This form of rainwater harvesting typically falls into the realm of landscape design/construction professionals and involves studying the land and its natural water flows, with the goal of directing runoff to plant basins or areas where it can be infiltrated directly into the soil or via a pervious pavement or other surface. We’re going to see a lot more of both varieties of rainwater harvesting in the next decade, as urban water crises occur more frequently,  requiring project designers to come up with new water-conserving approaches for building projects. Read more in Chapter 9 of my new book, Dry Run, available on this site for free download.

Posted by Jerry on 08/09/2010 at 09:17 AM

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Avoiding Future Urban Water Management Crises

We know that water supply, treatment, distribution and wastewater treatment uses significant amounts of energy, in California nearly 20 percent of all electricity use. We also know that “nega-gallons” of supply from water conservation and efficiency programs are far cheaper than most energy efficiency programs now in place around the country. We also know that pricing is a key tool for reducing water demand, one that is just beginning to be utilized in many parts of the country. In Las Vegas, there are programs in place to reduce water use by 50 percent from recent demand, to meet a dwindling supply of water from the Colorado River’s Lake Mead, its main water supply source, using four main methods: pricing, education, incentives and regulation. The water-energy nexus will continue to challenge both water and energy planners in the decades ahead, where there is not enough energy for future water demands and not enough water for future energy demands, unless we dramatically change how we approach both issues. By recognizing their “Siamese twin” interaction, we’ll be able to make better water resource decisions for the future. Read more in Chapter 4, now available for download from this web site.

Posted by Jerry on 08/09/2010 at 09:06 AM

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Monday, August 02, 2010

The Water/Energy Nexus:  Saving Water Saves Energy & Reduces Emissions

In the production of energy, water provides cooling for thermoelectric power plants, both fossil and nuclear and – surprisingly—also for concentrating solar power plants. This is one reason why concentrating solar power is a bad choice for most desert areas, since their groundwater resources are so precious (and a good reason why it will never get off the ground in most parts of the world!)

The water/energy connection is particularly strong in places where water has to travel long distances from source to city, such as Southern California. Water supply and wastewater treatment account for 19 percent of California’s statewide electricity use and 32 percent of all natural gas use, generating 106 million annual metric tons of CO2-equivalent emissions.

Recognizing the water/energy nexus, the City of San Antonio’s energy supplier and water agency partnered to combine wastewater treatment costs with power plant cooling costs.  One of the city’s sewage treatment plants discharges its highly treated sewage into a lake that provides cooling for the nearby electric power plant.

In the coming decades, the water/energy nexus will continue to challenge water and energy planners, and I expect to see more such partnerships and creative undertakings in the future. One way to avoid taxing the energy and water systems is to rely much more on photovoltaic solar and wind power to provide the electric energy for moving and treating water. Read more about the water/energy nexus in Chapter 4 of my new book, Dry Run: Preventing the Next Urban Water Crisis, released last June by New Society Publishers.


[Table:  4.1 ]
Energy use for the water cycle in Southern California is dominated by conveyance (transportation), because of both the distances involved and lifting water more than 3,000 feet to get over the Tehachapi Mountains. In Northern California, most of the water supply flows by gravity from the Sierra Nevada to the urban centers.

                                                         

Supply Component	Northern California kWh/million gallons	Southern California kWh/million gallons
Conveyance	150	8,900
Water Treatment	100	100
Distribution	1,200	1,200
Wastewater Treatment	2,500	2,500
Regional Total	3,900	12,700

Source: California Energy Commission, California’s Water-Energy Relationship, Final Staff Report, 2005, available at: www.energy.ca.gov/2005publications/CEC-700-2005-011/CEC-700-2005-011-SF.PDF.

 

Posted by Jerry on 08/02/2010 at 03:34 PM

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