The water we use every day keeps our bodies hydrated, our homes clean, and our communities functional. If many of us give little thought to where our water comes from before it reaches the tap, even fewer of us have a good idea of where it goes once it has passed down the drain. The San Diego region imports more than 80 percent of our freshwater from regions hundreds of miles away. You may already know that much of the water in your glass passed through the Grand Canyon on its way to your home, but do you know where it goes next?
Water that has been recently used in your home, a business, or in industrial processing is known as “wastewater.” Once it has passed down the drain, wastewater is sent to a treatment facility for processing. At the wastewater treatment facility, various biological and chemical processes are used to remove some (but not all) of the pollutants from the water. The partially treated wastewater is then discharged into the ocean, a river, or other waterway. Here in San Diego County, there are several wastewater treatment plants of various sizes that work to process and discharge our wastewater. The largest of these is the Point Loma Wastewater Treatment Plant, which currently processes over 150 million gallons of wastewater each day before discharging the partially treated wastewater into the Pacific Ocean through a deep ocean outfall several miles off the coast of Point Loma.
Though the San Diego region is heavily dependent on imported water to provide over 80 percent of our freshwater needs, very little of the water we receive is used more than once before it is discharged into the ocean. In general, cities “upstream” of us on the water supply chain – that is, cities who use our freshwater before we do – are required to treat their wastewater to a higher standard (called “secondary treatment”), and then return that treated water to the environment for “downstream” users like us. Because – as a coastal city – San Diego is at the end of the line in terms of water supply, and has no downstream neighbors dependent on using its wastewater flows, our region does not treat wastewater to secondary treatment standards. Instead, we treat our wastewater to a lower standard (called “primary treatment”) and then discharge it into the ocean. The water we use in our homes, gardens, offices, restaurants, and more has been used and discharged many times by upstream cities before it reaches San Diego. Historically, our city has done very little recycling of that same water. Instead, we dump it into the ocean after one use and remain heavily dependent on imported water that has already gone through many uses and treatment processes, and has traveled far distances at great environmental and economic cost. Thanks to the ongoing implementation of Pure Water San Diego, our region is at long last poised to recycle a meaningful amount of our wastewater, providing a local, sustainable supply of freshwater to San Diegans.