The students at the University of Miami will know firsthand the importance of rethinking the way we handle wastewater and water with a Net-Zero water treatment system on site. The project showed the viability and feasibility to take buildings off the water grid to provide water recycling and how it can be achieved without raising the cost of high quality water.
The research team behind this Autonomous Net-Zero Water Project designed and built a 4-bedroom dorm located a “special interest” floor of Eaton Residential College on the University of Miami Campus. Dr. James Englehardt, principal investigator for the project, described one of the project's main goals: to be able to do this for a single stand-alone building (decentralized) with a low-energy and low-emission water-reuse treatment system. The engineering techniques used in this eco-friendly project allows many functions of water-monitoring, water quality control, and operation/maintenance of wastewater and water treatment systems.
This project, funded by a $2-million, multi-year NSF Emerging Frontiers in Research and Innovation grant, demonstrated the approach. Technologies considered for the project to remove ions or natural minerals, such as reverse osmosis (RO) or infrared distillation, in the water use too much energy. The multi-stage flow involved a pretreatment method of a settling tank, BioBarrier Membrane Bioreactor (to provide biological treatment and ultrafiltration of the wastewater to remove 99.9% of the contaminants), and holding tank. When water is needed, it passes through an iron-mediated aeration/vacuum ultrafiltration system, UV system and peroxone advanced oxidation with rainwater makeup. The water then passes through activated carbon and stored back in a holding tank. At this point, the water is tested to see if it contains any contaminants. To prevent minerals from accumulating to concentrations that are too high, they will recycle 80% of the water and dispose up to 20% of the treated water to the sewer, and use rainwater collected from cisterns to make up the difference. The recycled water meets drinking water standards, but used only for irrigation and other non-potable uses due to no current regulations for potable water reuse and made regulatory permission easier for this research project.
Englehardt explains that, on average in the U.S., water and wastewater conveyance costs consumers four times the amount of energy moving back and forth from centralized treatment plants. The project was to:
Study social motivations for adoption of net-zero water technology
Develop real-time risk detection technology using machine learning and evidence processing techniques
Monitor the total electrical consumption and compare the savings used for conveyance and desalination of water and wastewater in the US.
Allow treatment to focus on permanently destroying the pharmaceuticals and cleaning chemicals that go down our drains, removing them from the environment.
Replace the notion that we need to use “water rationing” and “low-flow” fixtures.
The concept of net-zero water buildings involves treating and re-using all of the wastewater from the building's sinks, laundry, toilets, dishwasher, and showers in four bathrooms and a kitchen. The students will use the treated water for everything but drinking and cooking – which this water will be supplied from a well. With no sewer to contend with, infrastructure is simplified. All the physical, chemical, and biological processes to remove these contaminants and produce environmentally safe treated wastewater happen within feet of the building and available for reuse, instead of pumping miles away to be discharged somewhere else.
'We're developing design principles for future buildings that are off the water and wastewater grids, and the basic research includes many aspects of system design. We selected the Bio-Microbics® BioBarrier® system based on its competitive cost and projected effluent quality, including our particular need to bring total nitrogen to below drinking water standards in the effluent. In fact, with the addition of alkalinity and ethanol feeders, nitrogen was never an issue, and the system ran trouble-free for the duration of the 2-year experiment with no attention other than chemical tank recharge,” said Englehardt.