Reverse osmosis based treatment of brackish water and treated wastewater is one of the key solutions for solving the global challenge of water scarcity due to population growth and climate change

This Cooperative Agreement award from the U.S. Department of the Interior Bureau of Reclamation, under the Water Desalination Research and Development Program (CFDA 15.506), aims to demonstrate a continuous pilot photobioreactor operation using sunlight to remove scaling compounds from reverse osmosis concentrate. The project team at Texas State University has developed a new photobiological process that utilizes brackish diatoms and natural sunlight to remove scalants such as silica, phosphate, and hardness metals. This enables additional freshwater recovery from treated reverse osmosis concentrate, reduces the concentrate volume to less than 5%, absorbs carbon dioxide, and produces beneficial algal bioresources. The total federal funding for this project is $480,201.37, with an award date of July 25, 2024, and an ultimate completion date of September 30, 2027. The goal is to advance water treatment technologies to augment the United States' usable water supply by reducing the costs, energy requirements, and environmental impacts of desalinating and treating impaired waters.

However, 15% to 25% of the feed water becomes waste stream, called reverse osmosis concentrate or brine, presenting a disposal issue, especially critical for inland communities. Higher water recovery is limited by membrane scaling due to silica, phosphate, and hardness metals, such as calcium, associated with the brine. The project team has developed a new photobiological process that utilizes the biology of brackish diatoms and natural sunlight to remove these scalants, enables additional freshwater recovery from treated reverse osmosis concentrate using secondary reverse osmosis, reduces the concentrate volume to less than 5%, absorbs carbon dioxide, and produces beneficial algal bioresources. This project seeks to demonstrate continuous pilot photobioreactor operation using sunlight and reduction of the reactor footprint.