APPLICATIONS FOR HARVESTED WATER

APPLICATIONS FOR HARVESTED WATER

Harvested water that has been properly filtered and stored can be treated for many non-potable uses. Regulations in some states and municipalities restrict the uses of harvested water and should be carefully checked for compliance before a system is designed.

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Toilet and Urinal Flushing

While it may seem counterintuitive to carefully collect and store rainwater or greywater to flush toilets, it is actually one of the best uses for harvested water. Toilets and urinals consume as much as 40-60% of water purchased for a typical office building. By supplementing or eliminating this wasteful use of potable water, “green” buildings not only reduce their municipal water bills, but also contribute to conserving a valuable, limited resource in our environment. The filtering and sterilizing steps included in the Water Harvesting Solutions systems turn greywater into clear, clean water, making it highly suitable for toilet flushing.

Landscape Irrigation

Using treated water to irrigate landscaping is one of the more common applications for rainwater harvesting systems. What could be more natural than carefully saving excess rainwater to water plants and lawns around a facility? This use of harvested rainwater is particularly effective in areas that experience rain events on a periodic basis throughout the irrigation season. These systems are designed to store enough harvested rain to bridge rain events by up to three weeks.

In areas where rain events are seasonal and long gaps are typical during a “dry season” greywater may be a better water source for supply. The most reliable sources of greywater are available in residential buildings with showers and lavatory sinks. For more information on greywater as a source, click here.

A properly designed water harvesting system will apply only as much treated water as needed by each irrigation zone. That amount is determined based on the evapotransporation or “ET” of the landscaping, which is calculated using the amount of rainfall, temperature, variations, humidity, wind, soil type and topography of the property.

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Cooling Tower Make-up

Many commercial buildings are cooled with systems using evaporative towers and cooling water systems that can be tremendous consumers of potable water. A typical commercial building with an evaporative cooling system can used 2-3 million gallons of water in a season to “make-up” water lost through evaporation and the “blow-down” cleaning cycle. In warmer climates, the consumption can even be greater.

Treated properly, rainwater, stormwater and greywater used for cooling tower make-up can save millions of gallons of water each year. Additionally, the condensate generated by the cooling system can be harvested, treated and sent back to the towers as a looped system.

Other Applications

Depending on the building’s location and function, other uses for the harvested water may be considered. During the Consulting Phase, Wahaso can help assess the most effective approach for managing the supply and demand of harvested water for any project.

  • Boiler Make-up: Boilers in a commercial building can consume thousands of gallons of water per day. Harvested water can serve as “make-up” for water lost in the heating cycle.
  • Fire Suppression Systems: Commercial buildings with can easily have 100,000 gallons or more of stored harvested water that can be readily available for an automatic fire suppression system or as an additional water source for pumping trucks in the event of a property fire. This stored bulk water could be especially important in communities with inadequate water pressure or water main capacity.
  • Industrial Applications: Buildings for water-intensive industrial use can also benefit from water harvesting. These buildings frequently have large roof and parking surface areas with a significant potential for capturing and harvesting rainwater. Even if the harvested water is a relatively small percentage of total use, its application can be part of an overall effort to reduce the building’s impact on the environment.
  • Clothes Washing: Harvested water may be useful in buildings doing large quantities of laundry – such as a dormitory or correctional facility.