Reverse osmosis (RO)-based treatment of brackish water and recycled water is one of the key solutions for solving the global challenge of water scarcity due to excessive drought, population growth, and climate change. While the RO process produces 75% to 85% of fresh water, 15% to 25% of the feed water becomes a waste stream called concentrate or brine. The management and proper disposal of brine is a critical issue in RO-based water reuse and desalination projects. To reduce the volume of brine and improve water recovery, an additional stage of RO treatment may be added. However, serious scaling due to the presence of inorganic scalants, including silica (SiO2), phosphate (PO43-), calcium carbonate (calcite, CaCO3), calcium sulfate (gypsum, CaSO4), and barium, becomes a major problem. Also, the impacts of wastewater-derived constituents, such as nutrients and trace organics including disinfection byproducts within the concentrate on the receiving environment is becoming a major concern. A novel photobiological treatment process using brackish diatoms has been developed recently. Diatoms naturally take up dissolved silica, along with macronutrients, including ammonia (NH3/NH4+), nitrate (NO3-), and orthophosphate, which are often present in RO concentrate. After the photobiological treatment, RO concentrate can be further desalinated with an off-the-shelf secondary RO process. Our previous proof-of-concept study showed the great promise of this approach using RO concentrates from a full-scale advanced water purification facility (AWPF) (Ikehata et al. 2018) and brackish groundwater desalination (Kulkarni et al. 2019; Ikehata and Kulkarni 2018) in California and New Mexico, respectively. One of the unexpected, but very interesting findings was the precipitation of calcium carbonate, which also happens to be another typical scaling factor in the RO process of brackish water and reclaimed water. This current study extended our proof-of-concept to RO facilities in Texas with the investigation of the removal of calcium carbonate, as well as reactive silica and nutrients.
This presentation is available to AMTA Members only.
Speaker
- Keisuke Ikehata
Company
- Texas State University
Event
- AMTA/AWWA Membrane Technology Conference, West Palm Beach, FL
Session
- AMTA/AWWA Membrane Technology Conference
Date
- 07/20/21
Media
Keywords
- Reverse Osmosis, brine, brackish
Reference
- 9710-DP2723