When most people think about water harvesting, they think of rainwater harvesting. While rainwater harvesting is the bulk of what water harvesting is these days, there are other methods and systems of water harvesting that are used in commercial and non-commercial settings. These systems include grey water harvesting, cooling condensate, and multi-source harvesting systems.
Before we discuss the individual systems, there is a brief distinction that needs to be made about these systems. There are two main types of water harvesting: active and passive.
Active water harvesting systems consist of mechanisms and other active means of collecting water and the filtering, pumping and storing systems involved.
Passive water harvesting is a water harvesting method that is designed primarily for environmental reasons and includes the creation of natural green roofs and biological catchments that capture and store water. Your water harvesting needs and goals will usually determine what type of system you use.
Rainwater harvesting is as old as civilization itself. Ancient civilizations, especially those in dry areas, built elaborate systems of basins, catchments, and canals to harvest and use water for agriculture and as drinking water.
Since the advance of modern municipal systems and water distribution, rainwater harvesting loss its use and appeal. However, with water supply issues increasing and therefore the overall cost of municipal water increasing, rainwater harvesting has seen something of a resurgence. There are both residential and commercial applications of rainwater harvesting.
Rainwater can be harvested in a variety of ways and can use the design of the building to aid in its procurement. Rooftops and stormwater catchments in parking lots and other ground surface areas are the most common ways that rainwater is harvested in commercial applications. New regulations around building stormwater management has pushed the obligation and expense of managing stormwater runoff to the property owners in order to reduce the strain on municipalities. In response, building owners have begun to seek ways to make use of water that they are obligated to manage anyway. Stormwater harvesting systems allow building owners to use stormwater to provide water for toilets and irrigate their landscaping, thus reducing the total cost of stormwater management.
Every building with an HVAC system generates a remarkable amount of water during the summer months. Cooling condensate is generated by the cooling coils of HVAC systems. The moisture in the air condenses around the cool coils and is usually discarded into the sewer. For the average commercial building, cooling systems generate hundreds of thousands of gallons of water per year and some systems generate at rates of 15 gallons per minute. This is obviously a great way to reduce total water consumption. Cooling condensate water harvesting systems are designed to capture, collect, store and put this water to use.
Grey water is considered “gently used” water. It is usually non-potable and comes from showers, sinks and other non-sewage uses. Grey water is a usually wasted and sent back to the treatment plant. New technologies and building designs have made it easier to harvest grey water and use it for things like toilets and irrigation. Because greywater will often contain contaminants like soaps and biological agents, it is subject to a number of regulations that until recently made it difficult to harvest and reuse without running into regulatory issues. However, newer water harvesting systems are designed to capture and treat grey water to regulatory standards.