Low Energy Baffled Bioreactor BBR-based Water Re-use System for Energy and Water Security
Dr. Christopher Griggs | U.S.Army ERDC
The overall goals of this project are to evaluate the use of a baffled bioreactor (BBR)-based greywater reuse system, capable of harvesting 8,000 gallons of freshwater out of greywater per day, at a power rating of 1-2 kilowatt per meter cubed (kW/m3), maintenance time of less than 2 hours per week, and recovery efficiency of 95%, and to assess the long-term system performance with respect to operation and maintenance (O&M) and energy demand. The research team will achieve these goals by performing a field-scale pilot demonstration, with “real” greywater from training areas, with specific objectives to include the following:
- Low energy demand compatible with solar energy (1-2 kW/m3),
- Minimal operator requirements and maintenance,
- Determination of the wastewater strength/ biological oxygen demand (BOD) / total nitrogen (TN) /greywater chemistry needed to maintain effective treatment rates (95% recovery), and
- Blackwater treatment/recovery capability.
BBR is the core component for the system. In principle, it uses Modified Ludzack-Ettinger (MLE) process with intermittent aeration to biologically remove pollutants including nutrients. It has a pre-anoxic zone to perform denitrification, an intermittent aeration zone to oxidize organic matter and ammonia (when the aeration is on) and denitrify residue nitrate (when the aeration is off), an internal settler to retain sludge, and a final clarifier to polish effluent. In the research team's previous test, its energy use to treat 1 m3 of wastewater is approximately 0.6 kWh, similar to that used in large, centralized treatment plants. The system includes a proven BBR technology for advanced wastewater treatment, a dynamic carbon filter for depth treatment, a contact filtration process to mimic conventional drinking water treatment, and a second dynamic carbon filter for polishing. Bleach is used for final effluent disinfection.
The successful completion of this project is expected to provide a demonstration of a simple but effective technology to mitigate risks of energy and water disruptions/security, showing the BBR treatment and energy advantages over high pressure/energy intensive membrane systems. This system will be in a deployable 20-ft shipping container, suitable for both forward operating bases (FOBs) as well as large, fixed installations. Its performance parameters, such as effluent quality, labor use, power use, and waste generation are significantly better than the military requirements, providing water resilience with minimal operator requirements and amenable to alternative energy sources such as solar.