As water conservation efforts across the United States continue to increase, building owners are no longer just looking for ways to reduce usage – they’re also looking for opportunities to reuse water when possible.
Greywater, which makes up between 30 and 50 percent of total wastewater, is nonpotable water from bathrooms and laundry areas. It is generated from showers, bathtubs, basins, and washing machines. Because of how it’s used, it’s often contaminated with soap, detergent, saliva, and dirt. Blackwater is classified as wastewater from a toilet; it contains bodily waste. Although greywater and blackwater aren’t drinking-water quality, they can still be used to flush toilets and urinals, in surface irrigation and cooling towers, and for laundry – if they’re handled correctly.
That’s where blackwater recycling systems enter the picture: These systems use a rigorous filtration, disinfection, and biological treatment process to rid blackwater of contaminants. Here’s how the process works:
- Once used, water moves from the building to a collection point
- The water is screened to reduce any solids down to negligible residue
- Air diffused into the water allows bacteria to consume contaminants
- An ultrafiltration process prevents particles, bacteria, and viruses from passing through
- Water is exposed to ultraviolet lamps, providing protection against pathogens
- Any total dissolved solids (TDS) and nutrients are removed
- The water is stored along with a chlorine residual to protect the water
Once this recycling process is complete, the treated water can be used for a variety of nonpotable applications.
When this water is being used within a commercial building, local regulations may require building owners to post signage that alerts tenants and occupants of its use.
Blackwater Systems in Action
The Solaire in New York City – a 27-story, 357,000-square-foot residential tower with 293 units – makes use of a blackwater system to reuse 100 percent of the building’s wastewater. After treatment, this recycled blackwater is then used for irrigation, cooling towers, and toilet/urinal flushing. It’s estimated that the system supplies 9,000 gallons per day for flushing toilets, 11,500 gallons per day for cooling tower water, and 6,000 gallons per day for irrigation.
By recycling blackwater, The Solaire also ensures that wastewater from its occupants isn’t sent to the municipal sewer system or discharged to rivers and streams. This ultimately lessens strain on New York’s water and sewer infrastructure (and reduces the building’s utility bills).
Because of the space requirements for blackwater recycling systems, it’s often easier to design them into a project during the construction phase; however, retrofitting them into existing buildings is possible.
New in Blackwater Systems
Municipal and state codes may be a hindrance to commercial building owners who are interested in reusing blackwater, depending on geographic location. In some cases, installation of a blackwater recycling system may require special permitting through the U.S. Department of Public Health.
But given recent drought conditions, some states like Oklahoma are implementing tactics to reuse wastewater citywide, whether it’s to water golf courses and school yards, fill lakes, or fight fires. According to The Pew Charitable Trusts, reclaimed water is also being used in the Northeast to make snow for ski resorts.
But even with these new water-conservation approaches in place, The Pew Charitable Trusts says that water reuse still only accounts for less than one percent of total water usage in the United States.