Some important benefits include creating a locally controlled, sustainable, and high-quality water supply and increasing water reliability because purified water is drought proof. Purified water also reduces dependency on water from the Sacramento-San Joaquin River Delta and helps protect the region’s groundwater supplies and environment. Recycling is good for the environment. The more recycled water we use, the less we need to take out of rivers, streams and groundwater basins. All water on the planet is reused. There exists the same amount of water on the plant as there always has been. Water is too precious a resource to use only once!

The treated effluent – already having gone through a two-step advanced process and safe enough for release to the San Francisco Bay — is further purified using three advanced purification processes: microfiltration, reverse osmosis and ultraviolet light.

Microfiltration
In this initial filtration process, treated effluent is forced through filtration membrane modules made up of thousands of hollow fibers, similar to straws. These fibers have very fine pores in the sides that are 0.1 micron in diameter, or about 1/300th the width of human hair. As the water is drawn through the pores into the center of the fibers, solids, bacteria, protozoa and some viruses are filtered out of the water.

Reverse Osmosis
During the reverse osmosis (RO) process, water is forced under high pressure through membranes with holes so small that a water molecule is essentially the only substance that can pass through. The process removes constituents such as salts, viruses and most contaminants of emerging concern, such as pharmaceuticals, personal care products and pesticides.

Ultraviolet Light
Now the water is very clean, but as a further safety back-up, the water is sent through chambers that emit strong ultraviolet light to inactivate any remaining viruses and break down some of the remaining trace organic compounds. Ultraviolet light is a powerful disinfection process that creates water of very high quality. The technique is often used to sterilize medicines, food and fruit juices.

Indirect Potable Reuse (IPR) – is adding purified water to augment groundwater or surface waters. Groundwater and surface waters are considered natural buffers before final treatment and distribution into the drinking water system.

Direct Potable Reuse (DPR) – is the delivery of purified water to a drinking water plant or a drinking water distribution system without an isolating environmental buffer.

A multi-barrier treatment process uses advanced technology to replicate the natural water cycle, only faster. This is being done at the Silicon Valley Advanced Water Purification Center (SVAWPC). The water purification process includes microfiltration, reverse osmosis, and ultraviolet light disinfection. An additional final Advanced Oxidation UV step would be added to the purified water if it were to be used for more than traditional recycled water uses such and to be used to augment drinking water supply, which is regulated by the Division of Drinking Water under the State Water Resources Control Board.