The Santa Clara Valley Water District is working on an innovative pilot project that uses the power of the sun, ozone and an artificial wetland to treat and dispose of wastewater produced during the process of purifying recycled water.
The district operates the Silicon Valley Advanced Water Purification Center (SVAWPC), the largest advanced water purification plant in Northern California. Purified water is a component of the region’s complex, integrated water supply portfolio to ensure continued safe, clean water for a healthy life, environment, and economy in our communities.
Plans to develop potable reuse projects have been unfolding steadily since the launch of the SVAWPC in 2014. The district’s goal has been to develop recycled water to provide for at least 10 percent of total county water demands by 2025. To achieve this, the water district plans to develop increasing quantities of advanced purified water to augment water supplies.
We have the technology to move us towards securing our future water supplies with recycled and purified water. Reverse osmosis is the second in a three-step process used to purify water, a process in which water is forced through sheets with holes so small that only water molecules could pass through. The process removes salts, pesticides, viruses, and other containments which end up in the reverse osmosis waste water, called “concentrate.”
The challenge before us is the treatment and disposal of the concentrate. The water district is investing in a research project to identify environmentally friendly methods for the management of the concentrate. The water district has partnered with University of California, Berkeley, NSF Engineering Research Center for Reinventing the Nation’s Urban Water Infrastructure, Stanford University, and the San Francisco Estuary Institute on a pilot project to study the use of sunlight photolysis, ozone oxidation, and a biological mat made of algae and bacteria to remove nutrients, metals, and contaminates from the concentrate. Ozone is also used to assist with the process by making contaminants weaker and easier to destroy.
The diagram below describes the treatment process. The pilot project is scheduled to sunset at the end of 2019. We expect the results will yield new and innovative solutions that could potentially be applied in other water reuse projects around the world.