Water reclamation plant supplies desert city with alternative

Located in a desert region with limited resources, San Diego’s North City Water Reclamation Plant serves a vital function. This $194 million facility is capable of treating up to 30 million gallons of wastewater per day to standards suitable for landscape irrigation, industrial processes and recreational uses like swimming and fishing.

The facility is the first large-scale water reclamation plant in San Diego’s history and represents the single largest system expansion in more than 30 years. Located in a business park/industrial environment, the plant was designed with extensive input from residents and businesses in the surrounding community.

The water reclamation project was necessary because more than 90 percent of San Diego’s water is imported from the Colorado River and Northern California. Water reclamation provides an environmentally sensitive and cost-effective alternative to using limited imported supplies.

The reclaimed water produced at the North City Plant will provide a reliable and uninterruptible source of water, available even during droughts, that can be used to keep golf courses lush and fountains full, thereby freeing potable water supplies for other uses.

The North City Water Reclamation Plant also provides additional wastewater treatment capacity for the region, lessening the demands placed on the 35-year-old Point Loma Plant, San Diego’s primary treatment facility.

The project was divided into smaller construction packages to help meet financial and scheduling requirements and was bid as 15 different construction packages to reduce costs and maximize local contractor participation. The contractors worked successfully in a limited area and completed their portions within budget and on time.

Now, plans are being made to repurify the reclaimed water from the plant to drinking water standards, blending it with San Diego’s potable water supply in the future.

This repurification program would use the tertiary treated water from the North City Plant for a potential new water source for the community by the year 2000. By incorporating reverse osmosis filtration and disinfection in a multiple-barrier process, the plant can provide an additional 20 million gallons a day of safe, clean water to city residents.

The architectural team worked closely with the community to develop a facility that looks like an industrial park, not a wastewater treatment plant. With translucent panels, skylights, huge columns and rounded corners, the plant resembles a college campus.

Native plants and flowers are planted in the demonstration landscaping gardens.

As mitigation for the biological and habitat disruption, the Metropolitan Wastewater Department purchased and set aside a pristine habitat covering 30 acres. Impacts like traffic and noise were addressed by limiting construction hours, employee work hours and delivery times.

During the treatment of wastewater, biosolids residue is produced. This organic product is beneficially recycled rather than being placed in landfills. By composting biosolids and combining them with soil amendments, San Diego is successfully returning valuable organic resources back into the ground, saving landfill space and providing mineral-rich fertilizer to the agricultural community.

Proximity to both commercial and residential areas has made odor and noise control a priority, so the plant is equipped with devices that control both. The design ensures there will be no detectable odors at the plant’s fence line. Fully-enclosed treatment basins were also used to control odors and resolve the nearby military base’s concern that its flight operations would be affected by birds and waterfowl attracted to open water structures.

Heat is used to break down organic material in wastewater during the treatment process. This produces large quantities of methane gas which have traditionally been burned off into the atmosphere. However, the city has devised a way to use this gas as a fuel to produce electricity and thermal energy at the facilities, ultimately saving residents millions of dollars in energy costs and preserving gas and oil that would have been used to create electricity.

To connect all elements of San Diego’s wastewater collection, treatment and disposal systems in the future, a citywide computer network called the Wastewater Operations Management Network (COMNET), is being installed throughout the projects at the Metropolitan Wastewater Department.

While manual controls are provided as a backup throughout the North City plant, when COMNET is fully operational, the city may consider operating the plant through a remote system.

Who helped: R.E. Hazard, Mingus Constructors, J.R. Filanc Construction Company, Hunter Corporation, Taylor Ball, Western Summit Constructors, C.E. Wylie Construction, Nielsen/ Dillingham, L.R. Hubbard, Westinghouse, California Sheet Metal