The Sanitation Districts of Los Angeles County operate ten water reclamation plants and one ocean design facility (Joint Water Pollution Control Plant). It offers tours to schools, clubs, organizations, and the general public of any of their facilities.
Today, February 23, 2010 I toured the San Jose Creek Water Reclamation Plant located next to the City of Whittier. It is the Sanitation Districts’ largest reclamation plant (100 mgd) serving a population of approximately one million people. Fifty (50) percent of the reclaimed water produced at this plant is reused, mostly for groundwater recharge.
Water recycling significantly reduces the Los Angeles Basin’s dependence on costly imported water and helps to replenish a large percentage of the ground water used by the region. The remainder water treated is put into the San Gabriel River and flows to the ocean.
In densely population areas the sewage is collected by a network of underground pipes that convey raw sewer to a wastewater treatment facility. Once in the treatment plant, wastewater goes through a series of actions which will help to clean the water. A wastewater treatment plant’s basic function is to quicken the natural processes by which water purifies itself.
At present the San Jose Creek Water Reclamation Plant uses a basic three (3) stages in the treatment of wastes: primary, secondary, and tertiary treatment.
Primary Treatment Process
It starts with the screening of the wastewater entering the treatment facilities. Water flows through a screen to remove large objects such as wood, rocks, rags, and even dead animals that may cause problems later in the treatment process clogging pumps and small pipes. After the sewage has been screened it passes into what is called a grit chamber where sand, grit, cinders and small stones are allowed to settle to the bottom to later be disposed. With screening completed and grit removed, the sewage still contains suspended solids which are gradually allowed to settle to the bottom of a long concrete rectangular sedimentation tank. The settled material is called primary sludge and it is mechanically remove from the sedimentation tanks.
Secondary Treatment Process
After the sewage leaves the settling tank in the primary stage, it is pumped to an aeration tank where it is mixed with air and sludge loaded with microorganisms that use oxygen to breathe and break down the organic matter. Sewage at the aeration tank remains for several hours allowing the process to removes up to 90% of the organic matter.
Meanwhile, the sewage flows from the aeration tank to another sedimentation tank to remove the microorganisms were they clump together, settle to the bottom, and are removed and recycled back into the treatment process.
Tertiary Treatment Process
The final step uses filtering and chemical treatment. This allows the water to be in better condition before it is put back into the water cycle system. The San Jose Creek Water Reclamation Plant has installed filters containing layers of anthracite coal, sand, and gravel which remove any remaining suspended materials from the water. The reclaimed water is then disinfected with chlorine.
After completion of all treatment processes, reclaimed water, is now free of harmful bacteria and viruses and is safe for human contact. Recycled water is then discharged to the San Jose creek destined to recharge groundwater supplies.
Any remaining chlorine in the purified water is removed prior discharge to protect aquatic life in the receiving environment. Water quality measurement and analysis are completed at laboratories located at the treatment plant to ensure reclaimed water meets all requirements of the Regional Quality Control Board.
The cleaning process from preliminary treatment to final disinfection prior reuse or discharge takes approximately ten (10) hours.
Information about the Sanitation Districts of Los Angeles County’s tours and facilities can be found at their website:
http://www.lacsd.org/about/wastewater_facilities/default.asp
The California Water Environment Association awards “best treatment plant of the year” to those facilities employing a state-of-the- art cleansing process, green technologies such as solar panels, and effluents meet stringent state quality standards. Check their website to know which wastewater treament plants have been awarded best in California. http://www.cwea.org/
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