On-Site Water Can Lead To Goal of Net-Zero Water

By H.W. (Bill) Hoffman  
OTHER PARTS OF THIS ARTICLEPt. 1: This PagePt. 2: Net-Zero, Re-Use Approaches Address Looming Water Problems Pt. 3: Treatment and Popularity of Re-Using Onsite WaterPt. 4: Product Showcase: Water Efficiency

Strategies for capturing water that facilities already have on site are gaining momentum. That’s because these alternate on-site sources of water can help facility managers reduce water and wastewater costs. The strategies can also assist facility managers in complying with initiatives ranging from stormwater control and restrictions on water use to wastewater discharge and implementation of green building programs. For some facilities with a goal of net-zero water, these alternate on-site strategies are a must. But they’re also applicable to any facility manager hoping to save money on water costs.

Many facility managers are familiar with the notion of net-zero energy buildings, but the net-zero water concept is still developing. The definition of a net-zero energy building is simple enough: It’s a building that, on an annual basis, generates as much energy as it uses. For net-zero water, the issue is slightly more complicated because potable water must be provided for human consumption. Current state and federal codes generally dictate that water consumed by humans must come from an approved potable water supply, such as a city or other public water supplier.

But there is also a significant difference and advantage when considering net-zero water: Once used, the resulting “wastewater” can be captured, treated, and reused for certain facility processes. There is also treated, reclaimed municipal water available in many communities that commercial facilities can use for irrigation, cooling tower makeup, and toilet and urinal flushing. Some purists may argue that the use of reclaimed water is not true net-zero, but many consider it part of the whole picture for reducing demands on freshwater supplies.

Whatever definition is accepted, achieving net-zero water requires three main strategies:

  • Reducing water use to a minimum.
  • Metering and submetering of uses and sources.
  • Making use of alternate sources of water.

Water efficiency applies to all uses — domestic, irrigation, cooling and heating, and other process uses. For example, some large facilities have converted to geothermal heating and cooling, thus eliminating cooling tower use that can represent a quarter to half of an office building’s use.

As for metering, the mantra of “If you don’t measure it, you can’t manage it” is especially true here. This involves metering all major uses, including irrigation, cooling tower makeup, water heating, boiler, chilled water, and other major uses. Metering also applies to both incoming potable and reclaimed water and the use of alternate on-site sources.

For a number of reasons, not all facilities can achieve net-zero water use, but all can capture and beneficially use the on-site water they are now “throwing away.” This means their facilities become more economically and environmentally efficient.

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  posted on 12/25/2014   Article Use Policy

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