- Hyperion sewage treatment plant
The Hyperion
Wastewater Treatment plant is located in southwestLos Angeles, California next toDockweiler State Beach onSanta Monica Bay . The largest such facility in theLos Angeles Metropolitan Area , Hyperion is operated by the City of Los Angeles, Department of Public Works, Bureau of Sanitation.History
Until 1925, raw sewage from the city of
Los Angeles was discharged untreated directly intoSanta Monica Bay in the region of today’s Hyperion Treatment Plant cite news |title=City of Los Angeles - Dept. Public Works| url=http://www.lacity.org/SAN/WPD/Siteorg/general/hyprnhist.htm ] .With the population increase, the amount of sewage became a major problem to the beaches, so in 1925 the city of
Los Angeles built a simple screening plant in the 200 acres the city had acquired in 1892 .Even with the screening plant, the quality of the water in the
Santa Monica Bay was unacceptable, and in 1950 the city ofLos Angeles opened the Hyperion Treatment Plant with full secondary treatment processes. In addition, the new plant included capture of biogas from anaerobic digesters to produce heat dried fertilizer .In order to keep up with the increase of influent wastewater produced by the ever growing city of
Los Angeles , by 1957 the plant engineers had cut back treatment levels and increased the discharge of a blend of primary and secondary effluent through a five-mile pipe into the ocean. They also opted to halt the production of fertilizers and started discharging digested sludge into theSanta Monica Bay through a seven-mile pipe .Environmental forces
The discharge of sewage effluent into
Santa Monica Bay changed the ecosystem so dramatically that by the 1970s, only worms and hardy clams existed in the ocean floor of the bay . The increasing volume of treated sewage being dumped intoSanta Monica Bay captured the attention of a group of concerned users of the bay, who started to observe a decrease in the number and quality of fish in the bay, sick dolphins and people cite news |title=Heal the Bay|url=http://www.healthebay.org/aboutus] . From this movement,Heal the Bay was founded by Dorothy Green in 1985.Heal the Bay joined the Environmental Protection Agency in a lawsuit against the city ofLos Angeles to force the sewage treatment done by Hyperion to comply with the Clean Water Act .Heal the Bay andEPA succeeded and by November 1987, Hyperion stopped discharging sludge into theSanta Monica Bay and by December 1998, Hyperion had a full secondary treatment plant. For its significance and impact to quality of life, in 2001 the Hyperion Treatment Plan was named one of the Top Ten Public Works project of the 20th century by the American Public Works Association cite news | title=American Public Works Association| url=http://www.apwa.net/About/Awards/TopTenCentury ] .Treatment system
The plant treats approximately 350-450 million gallons per day of raw sewage. The sewage undergoes both primary and secondary treatment.
The wastewater produced by houses, businesses, and industries, flows in the sewer system, separately from the storm drain system to the Hyperion treatment plant cite news |title=City of Los Angeles - Bureau of Sanitation |url=http://www.ci.la.ca.us/SAN/biosolidsems/flowchart/flowchart.html ] .
Once the wastewater reached the plant, the first treatment stage is to remove large objects such as plastic, rags, metals, and wood . The wastewater then flows into sedimentation tanks where about 15 tons of sand and other materials settle to the bottom of the tank and are removed every day.
The chemical treatment starts with the addition of coagulants to the wastewater to improve the settling of small particles. At Hyperion, the wastewater flows during one hour in underground tanks after the addition of coagulants . The settled solids are pumped to digesters and oil and grease are skimmed off the top of the wastewater .
After the removal of solids, the wastewater is pumped to tanks where aerators deliver 96% oxygen to the wastewater, providing microorganisms with the necessary conditions to decompose organic solids in the wastewater . The wastewater spends about one to two hours in the oxygen reactors .
Now that the microorganisms fed on most of the organics, they are able to settle to the bottom in quiescent conditions. The wastewater is pumped into settling, clarifying tanks where it stays for about four hours . After this time, about 90-95% of the solids have been removed from the wastewater and the effluent is clean enough to be discharged or recycled . About 94% of the water is discharged into the
Santa Monica Bay through a pipe 5 miles out from the shore and 190 feet deep . Approximately 30 million gallons of secondary effluent per day is pumped to the [http://www.westbasin.org/index.html West Basin Municipal Water District] where the water is filtered further and reused for various purposes.All the solids settled throughout the several stages in the treatment are treated in anaerobic digesters . The idea is to destroy pathogens before the sludge can be dumped in landfills. At Hyperion, the biosolids stay about 15 days in the digesters – enough time for the anaerobic bacteria to consume pathogens . One by-product of this process is the production of methane gas, which is captured and processed by a nearby power plant . After the “sterilization”, the biosolids have their water removed to reduce volume and thus reduce transportation costs . The dewatering is achieved by using centrifuges with variable settings and addition of polymers (Horenstein et al, 1990). Each 1% decrease in volume results in an economy of $1 million in disposal costs (Horenstein et al, 1990). The dewatered biosolids are then transported to landfills or to locations where it can be reused .
Future challenges
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