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Fit for use
- Tom Smith
In Beyond the Yuck Factor, North Carolina State University soil scientists investigate ways to safely treat wastewater for reuse. They work to show that small-scale wastewater reuse can be a way to ensure a safe and plentiful water supply in the face of projected nationwide water shortages.
Dr. Sushama Pradhan, a soils and onsite water technology research scientist, and Dr. Mike Hoover, a soil science professor and expert on onsite wastewater treatment, are leading research and outreach efforts to show that wastewater doesn't have to be pumped all the way back to a municipal treatment plant to be safely treated and reused.
This is particularly true for producing non-potable water — not used for drinking, cooking, showering or bathing.
Decentralized reuse can be successful in rural, suburban and urban communities. Even inside the city, where public sewers already exist, decentralized reuse can occur using a process called sewer-mining.
The Visionaire is a 35-story building with 251 condominiums in lower Manhattan. Even though the building is served by New York City's drinking water and sewer systems, the building has an onsite wastewater treatment system in the basement.
Non-potable water produced from the sewage are pumped back into the building after treatment and used for toilet flushing, grounds irrigation, water display fountains and chillers.
This diverts about half of the sewage that would normally go into New York City sewers. Once the water is treated, it is used multiple times. This reduces drinking water use by 48 percent in the high-rise community, thus saving money and also extending the city's drinking water supply by 30,000 gallons per day.
In North Carolina, a new city park in Raleigh provides reclaimed water for toilet flushing. Recycled waters are also being used to irrigate golf courses. A middle-school complex in Greensboro, N.C. is using harvested rainwater and treated wastewater for toilet and urinal flushing as well as for athletic field irrigation.
While the N.C. State scientists stress the efficiency of decentralized wastewater reuse, they also emphasize the need to treat water to the safety level that matches the water's intended uses, instead of treating all water to drinking water standards.
Getting river water clean enough to drink gets expensive and requires a lot of energy. Yet every day the average American uses 400 gallons of water treated to drinking water standards. Only three of the 400 gallons are consumed. More is used for cooking food and taking showers. However, the vast majority of the water we bring into our houses doesn't need to be treated to the same level as drinking water.
Locally treating water supplies based on their intended use via a decentralized wastewater reuse approach is more efficient and less expensive than many centralized reuse options.
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6. Cost of liability for the designer, user, operator and owner
On the small scale whether voluntary or mandatory there could be millions of unregulated systems that could provide for potential for serious issues. There is no way to control what or when something is put down a grey water drain let alone a closed loop system that allows for unregulated discharge and operation. On a small scale you certainly lose the dillution factor as a potential method or way of controlling these concerns.
1. Operator Error
2. Compliance by user and operator
3. When the start up funds dry up costs can sky rocket
4. System maintenance and repair
5. Terrorism by intentional dischage of a toxic substance
6. Cost of liability for the designer, user, operator and owner
On the small scale whether voluntary or mandatory there could be millions of unregulated systems that could provide for potential for serious issues. There is no way to control what or when something is put down a grey water drain let alone a closed loop system that allows for unregulated discharge and operation. On a small scale you certainly lose the dillution factor as a potential method or way of controlling these concerns.