Water conservation has become one of today’s most urgent challenges to sustainable design.
As the world becomes more aware and engaged in sustainability at a lifestyle and cultural level, the social and economic benefits of investing in water conservation are becoming more globally apparent and compelling. Solutions like low-flow plumbing fixtures can decrease a facility’s water bill, and an artificial wetland can ease burdens on city sewage systems and minimize potable water use. But there’s a missed conversation here. Greywater reuse and potable water preservation dominate these discussions, and while those solutions certainly carry merit, one important aspect of conservation is often neglected: process water.
That is, the water used in a building’s mechanical systems to heat, cool and otherwise support and maintain reliable operation. But just like the human body, buildings need clean water to function properly and efficiently. The challenge is that, because of its limited re-usability, process water is a major culprit for water use and waste in large buildings and industrial facilities. As it is passed through a system over and again, process water acquires corrosive elements—such as metals or salts—that taint it to a point where it is no longer pure enough for use. The resulting water, known as “blow down water,” has a high level of total dissolved solids (TDS), and can damage the system—creating major energy inefficiencies, increased need for water and, eventually, the need for expensive infrastructure replacements.
There is no one-size-fits-all solution. The trick is… addressing the issues on site rather than
pushing them down stream.
To successfully expand our water conservation efforts, we must begin incorporating ways to lessen the amount of water necessary for a building’s basic operation. There are several innovative approaches currently in use to help get the most out of the water we have already. Condensate recovery and rainwater catchment can reduce how heavily a system leans on potable water. In turn, water that is no longer usable for these processes can, once properly conditioned, be reused to flush toilets before being passed through another filtration and used again for drip irrigation. These solutions increase the lifespan and usability of water already existing in a system, and help further divorce a building from local water sources, conserving what’s available to the community.
Process Water Environmental Factors
A litany of variable environmental factors, based on building type, region and climate, also present unique challenges for process water conservation and reuse. For example, in many commercial buildings, this water is typically used to reject heat in the cooling tower or air handling unit. But this comes at a cost of lost water through evaporation and drift—water that is simply blown away by the wind and lost. These are waste scenarios that are preventable with infrastructure adjustments. However, finding ways on site to maintain or extend the re-usability of blow down water, which is in many cases dumped into the waste water drain, is critical to achieving greater levels of conservation.
The number of times water can be recycled through a system remains a great barrier toward conservation. However, increasing the number of process water reuse cycles can make a real impact. In California, for example, code requires that water be recycled a minimum of four times before it is discharged as blow down. With thoughtful design, we can easily achieve eight cycles, and truly innovative systems can achieve up to 20, depending on several environmental factors. If, for example, an average mixed-use development uses 60,000,000 gallons of water per year, and 25% of that alone go to heating. That’s 15,000,000 gallons per year. If we are able to increase the number of cycles the system can handle, this becomes an area where we can greatly reduce consumption.
Finding Solutions Before a Problem Arises
There is no one-size-fits-all solution. The trick to determining the best approach is finding that sweet spot between a building’s need and water reuse cycles, and addressing the issues on site rather than pushing them down stream. The percentages of process water vary greatly between industrial, healthcare and commercial buildings. In the coming months, we will address the process water issues of each of these facility types, to create a more concrete understanding of just how large of a challenge to water conservation this truly is.
For more information, please contact Neil Steiner.