It happens every summer. We grow to expect it. When the summer heat scorches our lawns, every town in America begins its yearly water ban, limiting the amount of water used and sometimes banning water activity outright, save for daily necessities. It seems so regular that it is hard to believe there was once a time where this didn’t occur. Yet a solution does exist: a process known as grey water recycling.
Grey Water: A New Solution to an Old Problem
Grey water is simply defined as water that has been “gently used” in sinks, baths and showers. It does not come from toilets or water with food waste, and yet it can make up eighty percent of the waste water generated by a single household. With a simple grey water harvesting system this useful water can be cleaned and sanitized for non-potable reuse such as irrigation. Grey water harvesting alone could potentially save a community thousands of gallons of drinking water for consumption, rather than wasting it on watering lawns.
From Grey to Clear: Making Recycled Water Clean and Safe
While grey water is an excellent source of outdoor watering and can also be used indoors for flushing toilets. However, regardless of the intended use, the water must be clean and safe before it can be exposed to the public. The process of reusing grey water for both irrigation and toilet flushing starts with harvesting the grey water and sending it through multiple filters to remove particulates. The water is then sanitized in order to ensure it is safe for public use. These precautions are necessary whether it is a small residential system, or a large-scale commercial system such as those designed by Water Harvesting Solutions (Wahaso).
Many of our projects at Water Harvesting Solutions involve clients who are pursuing Leadership in Energy and Environmental Design (LEED) certification. This program, developed by the U.S. Green Building Council, provides an independent, third party evaluation of a building to determine if it meets optimum performance in five areas:
- Sustainable site development
- Water savings
- Energy efficiency
- Material selection
- Environmental quality
Each performance area is assigned a set number of points which are accrued through meeting various criteria. These points are added up to determine if the building has achieved LEED certification. To certify a new building as “green” requires 40-49 points. More points are required to achieve the higher certification levels of Silver (50-59 points), Gold (60-79 points) and Platinum (80 points or more). Those higher certification levels almost certainly must include achievements in categories related to water conservation.
The water efficiency goals of the LEED program encourage smart water use both inside and outside of the building and can provide up to 12 possible points toward certification. In the area of Water Savings points can be accumulated in the following categories: 1) water efficient landscaping, 2) innovative wastewater technology and 3) water use reduction.
Harvested water can be a key component to obtaining LEED water savings points. For example, using captured rainwater or greywater for irrigation can provide points for the “water efficient landscaping” category. A 50% reduction of potable water for landscaping is worth two LEED points and a 100% reduction is worth four points. Water harvesting can also be used to gain two points in the “innovative wastewater technology” category. Reusing rainwater and greywater not only helps to reduce potable water consumption, but it also reduces the amount of water sent into the municipal storm system. Finally, up to four points can be awarded for overall water use reduction (irrigation is not included since it has a dedicated category.) A baseline for water usage is calculated for the building and the amount of points received corresponds to the amount of water saved:
- 30% reduction from baseline = two points
- 35% reduction from baseline = three points
- 40% reduction from baseline = four points
Additionally, water harvesting can earn points in the area of Sustainable Site Development. Harvesting stormwater for reuse can earn one point for minimizing run-off and one point for reducing the amount of contaminants that enter the storm system.
Our most efficient systems often capture multiple sources of on-site water for multiple uses. So a single system might capture rainwater, greywater and condensate to flush toilets and irrigate landscaping, saving as much as 90% of the total municipal water an office building would otherwise use. These systems can earn points from all four categories and help boost a project into the Gold or Platinum point levels.
The benefits of LEED certification are both environmental and financial. Not only does reducing water consumption help to conserve a vital resource, but it also reduces costs for municipal water use and stormwater management. LEED certification is also shown to increase a property’s resale value, making the investment in a water harvesting system a winning proposition.