Overcoming water scarcity and meeting future water demand for rapidly growing populations are some of the biggest challenges facing the water industry, scientific community, and government agencies. To achieve the goal of reducing water scarcity and meeting demand water utilities and agencies have looked to rely on more unconventional and local resources such as recycled wastewater, brackish groundwater, and brackish surface water to bolster drinking water supplies. These supplies are most effectively treated with reverse osmosis (RO) at advanced water purification facilities (AWPF) or brackish water desalination facilities (BWDF) which can obtain 75% to 85% recovery of highly purified water. While the RO process is advantages for producing water from those? unconventional water sources it also produces a concentrate/brine which is filled with inorganics (e.g., metals, nutrients) and organic compounds [e.g., disinfection by products (DBPs), pharmaceuticals and personal care products (PPCPs)] (Romeyn et al. 2015). The RO concentrate (ROC) needs to be properly managed using methods such as surface water discharge, ocean outfall, evaporation ponds, and deep well injection. Many facilities are built with cost effective ROC management methods in mind; however, these choices are limited for facilities located inland which do not have access to ocean outfall, the least expensive management method (Panagopoulos et al. 2019). Whether it is ROC minimization in order to minimize process costs or maximize water production facilities are looking for methods to increase water recovery. Currently technologies such as antiscalants, chemical softening, implementation of ion exchange to remove scalants, and variations of RO processes enhanced with vibration and precise control of concentrate discharge and non-RO desalination processes have been proposed and tested to improve the water recovery for RO facilities (Venkatesan et al. 2011; Subramani et al. 2012; Efraty et al. 2011; Hancock et al. 2013). The methods above are highly energy and/or chemically intensive and often require complex process control and do not offer overall removal constituents such as nutrients, organics, or metals. Alternatively, the incorporation of a diatom based photobiological reactor with secondary RO treatment recently introduced in 2017 (Ikehata et al. 2017; 2018a; 2018b; 2018c; 2019) is one of the newest enhanced water recovery methods. Increased water recovery could be achieved with the implementation of a photobiological reactor containing brackish diatoms which remove scalants (e.g., silica, calcium carbonate), nutrients (i.e., ammonia, nitrate, and phosphate), and organics (e.g., DBPs, PPCPs); thus providing a low energy alternative with the potential production of valuable products from algal biomass. In bench scale testing the diatoms have performed well in AWPF and BWDF ROC’s; However, a long-term continuous flow pilot scale feasibility study has not been conducted. To perform such a pilot study the fabrication of a 45-gallon acrylic glass continuous flow photobioreactor and the construction of a 100-gallon per day RO skid is underway. The first run of the pilot study will be performed under light emitting diodes (LEDs) inside a full-sale brackish groundwater desalination facility in Texas. The flow rate of the photobiological reactor will vary between 24 and 135 gallons per day with a hydraulic retention time of 24 to 8 hours, respectively.
This presentation is available to AMTA Members only.
- Jacob Palmer
- Texas State University, San Marcos
- AMTA Fellowship Recipients: Advancements in Membrane Research - Part 2, Online
- AMTA Fellowship Recipients Series
- Concentrate Management, Water Recovery, Photobiological Process