Sewage Treatment in Los Angeles – Where Does the Waste Go?

City Seal / LA Sanitation Logo

Every time you flush your toilet you use the City of Los Angeles’ sewage treatment infrastructure. But what exactly happens to that waste once it enters the sewer system and where does it go? Those are just a few of the questions that I sought to answer when I arranged a tour of the Bureau of Sanitation’s Hyperion Treatment Plant (HTP), located on the coast in Playa del Rey.

I arrived at the plant in the early afternoon and checked in at the Los Angeles Environmental Learning Center (ELC). There I met my tour guide, Nancy Carr, who provided some background information about the plant before guiding me and several other people around the facility.

I find that tours such as these are really hit or miss. Sometimes you’re in the hands of someone who knows their subject and understands how to explain it in lay language. At other times you’re not. Fortunately for me and countless others, Nancy falls into the first category. She was personable, highly knowledgeable and willing and able to answer our questions.

The HTP is a massive 144-acre facility that serves 3.3 million people living in Los Angeles and 29 contracting cities. The L.A. Bureau of Sanitation also manages three other sewage treatment facilities, including the Terminal Island, Donald C. Tillman and Los Angeles – Glendale Water Reclamation Plants.

Hyperion Treatment Plant - aerial view

Photo from City of Los Angeles Bureau of Sanitation

The Sewage Treatment Process

Preliminary Treatment

The Hyperion Treatment Plant is fed by four main sewer lines, which together carry approximately 350 million gallons of wastewater into the facility on a typical day without rain. After entering the plant, the raw sewage undergoes preliminary treatment in the headworks, which removes large solids, such as plastic and rags, using a series of mechanical screens and bars. According to Nancy, workers have pulled a strange assortment of items out of the headworks over the years, such as a 17 foot long pole, a bowling ball, money and a 2×4.

This was definitely one of the more unpleasant stops on the tour. Not only can you see the raw sewage flowing through this part of the plant, you can smell it too. And let me tell you – that’s one unpleasant odor!

Hyperion Treatment Plant - Headworks

Hyperion Treatment Plant – Headworks

Hyperion Treatment Plant - Headworks debris removal

Hyperion Treatment Plant – Headworks debris removal

Primary Treatment

After leaving the headworks, gravity moves the sewage to primary treatment settling tanks, which separate sludge from the water. Any waste that does not sink to the bottom of the tanks is skimmed from the surface. Unlike the headworks equipment that is installed within an enclosed building, the primary treatment tanks are built outdoors, below grade. To reduce odors they’re covered.

The transfer of sewage from primary to secondary treatment is made possible by the Intermediate Pump Station, which uses the “largest wastewater related Archimedes screw pumps in the world” to move the liquid from the settling tanks to a sufficiently high elevation that gravity can transport it to secondary treatment and beyond. If you’re not familiar with this mechanism, it consists of a screw type device encased in a pipe that moves water when turned.

Archimedes Screw

Archimedes Screw with ball. © Silberwolf / Wikimedia Commons / CC BY-SA 2.5

Secondary Treatment

Secondary treatment begins inside large reactor tanks, where the bacteria rich wastewater is oxygenated to breakdown organic solids remaining from primary treatment. “These ‘plumped up’ bacteria settle to the bottom of the tanks where they are sent to the clarifiers for final settling and collection.” Since the effluent is no longer as pungent, the outdoor clarifying tanks are open to the air.

Wastewater Disposal in the Santa Monica Bay

After secondary treatment is complete, most of the effluent is pumped through a 12” diameter, five-mile long pipeline that empties into the Santa Monica Bay. The remainder is further processed at the West Basin Water Recycling Plant in El Segundo to provide water for industrial applications and landscape irrigation.

If you’re wondering what happens to rainwater and runoff from residential and commercial irrigation, it flows into a completely separate storm water system. That water is not treated and flows directly into the ocean, which is why it’s so important that people don’t dump chemicals and other pollutants down storm drains.

Biogas and Biosolids

Aside from non-potable water, the HTP produces other valuable byproducts, including biogas and biosolids. The plant has 20 digesters on site, each of which processes 2.5 million gallons of waste per year. These structures are 110 feet tall, 40 feet of which are underground so as to minimize their profile and maintain views for neighboring properties.

The large, egg-shaped digesters process the solids removed from sewage during primary and secondary treatment. That bacteriological process produces approximately 8 million cubic feet of methane gas everyday, which is used to generate electricity at the Scattergood Steam Power Plant located right next door to Hyperion. At the same time, the digesters transform biosolids into “a pathogen-free Class A organic product, suitable for many landscaping and agricultural applications.”

Hyperion Treatment Plant - Digesters

Hyperion Treatment Plant – Digesters

Transforming raw sewage into treated wastewater clean enough to protect the Santa Monica Bay, as well as harnessing the treatment process to generate power and produce fertilizer, are significant improvements over what used to happen at the plant. According to a 1995 LA Times article, prior to 1987 “the City of Los Angeles was pumping untreated sludge about seven miles off the coast of Santa Monica, in what scientists agree was an ecological catastrophe.”

Speaking of fertilizer, Los Angeles sends approximately 450,000 tons of treated biosolids produced every year at Hyperion to city-owned Green Acres Farm, located in Kern County. Farmers till the sludge into the farm’s soil to fertilize crops such as wheat and corn.

Green Acres Farm

Photo from City of Los Angeles Bureau of Sanitation

As you might expect, that arrangement was controversial in Kern County due to public fears about the perceived health hazards of applying human waste to open farmland. The City of Los Angeles spent over a decade fighting attempts to stop the transfer and use of treated sludge on the farm and finally prevailed in court on December 5, 2016.

As I toured the plant I couldn’t help but be impressed by the sheer magnitude of the sewage treatment facility. But then, it’s exactly what you’d expect to find in a large city like Los Angeles. It takes a lot of machinery, some chemistry, trained staff and a good deal of money (approximately $70 million / year) to turn massive quantities of human waste into a less environmentally destructive state, in addition to a resource with societal benefits (i.e. the non-potable water, power and fertilizer mentioned above).

Hollywood Calls and Good Design

The Hyperion Treatment Plant periodically serves as a backdrop for films and television shows. If you let your imagination run wild you can certainly understand why location scouts would covet the unusual structures and spaces found on the property. Nancy informed us that it’s been featured in Battle for the Planet of the Apes, Solient Green, Logen’s Run, The Terminator and the X-Files, among other productions.

While the plant is not as well known from a design perspective as the Donald C. Tillman Reclamation Plant, many of its key structures were actually designed by the same architect. The HTP’s major expansion and redesign, completed in 1998 and spearheaded by DMJM architect Anthony Lumsden, FAIA (1928-2011), gave the facility its distinctive appearance that we’ve come to recognize today.

Detail of the Hyperion Treatment Plant

Detail of the Hyperion Treatment Plant designed by Anthony J. Lumsden, FAIA (1998). Photo by the architect.

Looking Towards the Future

We concluded our tour where it began, back at the Environmental Learning Center, which received LEED Gold certification from the U.S. Green Building Council when it opened in 2013. There Nancy walked us through the exhibits and explained how the center supports the city’s environmental goals related to solid resource management and sustainable water education.

If you want to see first hand how the City of Los Angeles treats its sewage, I highly recommend touring the facility and spending time exploring the ELC. It’s a great way to learn about your personal “…role in Clean Water Treatment and Conservation, Watershed Protection and Solids Resources Management.”


Where: Hyperion Treatment Plant, located at 12000 Vista Del Mar, Playa Del Rey, CA 90293

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