How clean is LA’s water? INFEWS Trainees head to Los Angeles Aqueduct Filtration Plant to find out!

LAAFP engineers Vee and Jackie give an overview of the filtration steps at the plant.

LAAFP engineers Vee and Jackie give an overview of the filtration steps at the plant.

There is a public stigma that tap water is not fit for drinking. And given the experiences of people in third world countries battling bacterial and viral infections to residents in Flint, Michigan being exposed to high levels of lead and other pollutants from water contamination, can you really blame anyone who feels this way? Los Angeles Department of Water and Power (LADWP), however, claims that the tap water in the City of Los Angeles is safe for consumption and is, in fact, held to a higher standard than bottled water. This past Friday, INFEWS trainees had a chance to get an inside look at the practices that bring Angelenos clean drinking water every day, by touring the LADWP’s Los Angeles Aqueduct Filtration Plant (LAAFP) in Sylmar, California. We were lucky to have Vee and Jackie, engineers at the plant, lead the tour and explain how water is cleaned and distributed throughout Los Angeles.

With a capacity to treat up to 600 million gallons of water per day, LAAFP supplies 60-70% of drinking water for 3.8 million residents of LA. Most of the water, about 85%, is imported from the Owens river in the Eastern Sierra Nevada Mountains via the 338 mile long Los Angeles Aqueduct, the San Francisco Bay Delta via the 700 mile long California aqueduct, or it is supplied to LA by the Metropolitan Water District of Southern California, a water wholesaler which sources water from the Colorado River and Northern California. Additional groundwater from a massive underground reservoir located under the San Fernando Valley is brought in. Once the water reaches the filtration plant, it only takes about 30-45 minutes for it to enter the city’s water main system. So what happens in this short time frame that ensures the safety of LA’s tap water? Check out this short (and adorable) video by LADWP and keep reading to find out!

The first step is a screening process which removes large debris like twigs, rocks and leaves. Next, fluoride is added to the water to promote oral health. Water then undergoes ozonation, the process of bubbling ozone into water, which helps smaller dirt particles clump together, kills bacteria, and improves the smell and appearance of water. Ozone molecules are made by subjecting oxygen to high electrical voltage. To supply the plant with the oxygen need for this process, LAAFP has a large oxygen plant which cryogenically separates air to produce pure oxygen. After interacting with ozone, the water undergoes a rapid mixing with treatment compounds that help remove tiny particles. Once mixed, the water travels to flocculation basins to slow the flow down and further clump particles together for easier filtering. From here, water is run through biologically-active anthracite coal filters, which remove large particles created during flocculation and sterilizes bacteria that may be in the water. These filters are frequently cleaned by a process called backwashing. Water from this process is moved to an underground pond where impurities are allowed to settle before recirculating the water through the whole filtration process again. With frequent cleaning, these coal filters can be used for up to 30 years.

Clear, filtered water after being chemically treated.

Clear, filtered water after being chemically treated.

Once the water is filtered, the flow continues to the Dr. Pankaj Parekh UV Disinfection Facility where pathogens like giardia and cryptosporidium are sterilized. Finally, chlorine and ammonia are added in small amounts to form chloramines which protects water as it travels to its final destination, whether that be straight to consumers or to a reservoir for storage. None of the operations at LAAFP would be possible without 24/7 surveillance from the control room where water treatment operators monitor and adjust water conditions as needed at each step. INFEWS trainees gained insight into these processes by viewing each step from the control room all the way to the UV Disinfection Facility, and we were truly impressed by the scale and care put into these operations.

Inside the Dr. Pankaj Parekh UV Disinfection Facility where UV disinfection of water removes pathogens like giardia and cryptosporidium.

Inside the Dr. Pankaj Parekh UV Disinfection Facility where UV disinfection of water removes pathogens like giardia and cryptosporidium.

Perhaps even more stunning is the Los Angeles Reservoir which contains up to 3.3 billion gallons of water and sits in the back of the LAAFP. The color of the the reservoir is particularly interesting: a greyish-black, rather than the natural blue we expect. The peculiar color of the reservoir comes from 96 million black “shade balls” which lie on top of the reservoir. The idea was first proposed by LADWP biologist Brian White who envisioned them as a way to save water and improve water quality from reservoirs. The balls do this by creating an insulating layer on top of the reservoir, which helps keep the water cool, in turn reducing evaporation and making it less susceptible to bacterial and algae growth. They also prevent a sunlight-dependent chemical reaction that can produce harmful substances. Although it seems like a large tarp/covering could be a more straightforward approach towards these goals, it is estimated that the balls, which are very cheaply made from plastics, saved Los Angeles $250 million dollars. One can’t help but wonder if the plastics, which require large quantities of water to manufacture and could be harmful to the environment once they’re thrown out, are a sustainable solution. However, scientists have estimated the amount of water needed to manufacture the balls and the amount saved through their use and found that it would take at least 2.5 years of use to recover the water used to make the balls. LADWP plans to replace the balls and recycle the old ones every 10 years, easily making up for  water consumed during their production.

Although this approach is innovative, ultimately, LA has saved the most amount of water in recent years through water conservation, both mandatory and incentivized. Water is becoming more and more scarce, even from imported sources, so LADWP offers financial incentives from installing water-saving shower heads, toilets, and washing machines. Water-saving toilets alone save LA more than 14 billion gallons of water each year! So, consider upgrading to water-saving appliances (and getting a sweet hundreds-of-dollars rebate from LADWP) to help conserve our water.

All-in-all, with water that’s cleaner than big name bottled water coming from our very own Los Angeles Aqueduct Filtration Plant, save yourself a buck and cut down on single-use plastics by reaching for the tap next time you’re thirsty.

Post and pictures submitted by Jack Hoeniges and Priera Panescu. This blog is part of the INFEWS social media series “FEW and Far Between”.