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Making the Most of Wastewater

Delta Diablo, a wastewater recovery center in Antioch, California has become a showcase for how to save water and energy, while turning 12 million gallons a day of wastewater into something usable.

Written by Nick Hansen Published on Read time Approx. 6 minutes
Recycled water can be seen cooling exhaust steam at the Delta Energy Center (Calpine, Pittsburg) situated next to Delta Diablo in Antioch, California.Nick Hansen

What does it take to be a water resource recovery leader? Easy, first recover as much water as possible from wastewater influent; second, utilize the resources in the waste to do something sustainable; third, recover power used by some renewable process; and fourth, be a leader while doing so.

Who comes to mind when this is applied? Delta Diablo.

Located in Antioch, California, Delta Diablo is a water resource recovery leader. They create high-quality, recycled water for parks, schools, sporting facilities and industrial use. They receive fats, oils and grease from restaurants and a local commercial rotisserie establishment to aid in biogas production in digesters and have also installed two massive solar arrays to generate clean electricity from the sun. On top of that, Delta Diablo is the lead agency for recycled-water policy change in the western United States and are staying tuned in to their local communities in the process.

But first, why should we think about a wastewater treatment plant as a water resource recovery facility instead? The response is simple. It just makes sense. We need to view these important assets in our communities for what they actually do: recovering resources.

Delta Diablo began to transform the industry 16 years ago with the state’s first industrial recycled water facility. Dean Eckerson, resource recovery services director at Delta Diablo said, “It’s our duty and responsibility to our customers.”

Delta Diablo provides resource recovery services for the city of Antioch, city of Pittsburg and the unincorporated community of Bay Point, serving nearly 200,000 people. They process 12 million gallons a day of wastewater and turn it into a variety of reusable things. Delta Diablo also operates a household hazardous waste collection facility to keep toxins out of the environment, such as old home and garden products – automotive fluids, paint, personal care products, e-waste (electronic waste) and a variety of other things.

But that’s not all, Delta Diablo is also responsible for street sweeping – “It’s an important pollution prevention function provided” to their communities, they report.

Recycled Water

Large water pumps supply recycled water to numerous customers throughout distribution pipeline at Delta Diablo in Antioch, California. (Nick Hansen)

Large water pumps supply recycled water to numerous customers throughout distribution pipeline at Delta Diablo in Antioch, California. (Nick Hansen)

When it comes to reusing water, Delta Diablo is near the top. Situated next to the Delta Energy Center (Calpine, Pittsburg) Power Plant Project, Delta Diablo is required to provide recycled water for power plant cooling towers. Calpine built Delta Diablo’s state-of-the-art recycled water facility in 2000. Recycled water is plumbed to the energy centers and circulated through the cooling towers to cool exhaust steam from their turbine generators.

Ninety percent of the recycled water produced at Delta Diablo is pumped to two power plants – Los Medanos Energy Center, which produces up to 572MW power and Delta Energy Center, which produces 880MW power.

The remaining 10 percent of recycled water produced is plumbed through a pipeline that extends deep into Pittsburg and Antioch and provides for landscape irrigation at two golf courses (Delta View Golf Course in Pittsburg and Lone Tree Golf Course in Antioch), 12 city parks, 16 schools in Pittsburg Unified School District, City Hall and Civic Park in Pittsburg. The recycled water pipeline was strategically placed to be close to parks and sports fields so that when they were ready to utilize recycled water, it was already available.

Delta Diablo operates a residential recycled water fill station which gave away 2 million gallons to nearly 500 permitted users in 2015. The board of directors said they provide this “service on a complimentary basis for users to supplement their existing irrigation water supplies.”


Six years ago, just as many Bay Area homeowners saw the benefits of installing solar at home, Delta Diablo brought those ambitions to fruition. Five large solar panel shade structures were built, providing 450kW for their plant operations building, cutting a large percentage of their power needs. The array was set up over the employee parking lot, keeping employee cars cool under the blazing sun.

On the treatment plant side, the anaerobic digester (think of it like your gut) produces methane gas that is used in a cogeneration facility to produce 800kW. This power is utilized in the treatment to keep the treatment plant moving.

Recently, their co-digestion process was upgraded to receive fats, oils and grease – FOG as it is known in the industry – which helps produce more methane in their digester. By contracting with local grease haulers, Delta Diablo can receive up to 10,000 gallons (45,460 litres) per day, five days a week. This has virtually eliminated any grease buildup in their collection system as restaurant FOG is injected into the digester where it goes to work immediately.

Three digesters receive this slurry of sludge, FOG and food scraps – all of which aid in biogas creation. This operational change improved the quality of the biogas.

Greg Kester, director of renewable resource programs at CASA, told the California Water Environment Association, “There has been a steady increase in co-digestion, especially with FOG and in some cases, food wastes. New costs for co-digestion of FOG are pretty minimal, generally. But through the use of existing digesters, new anaerobic digesters generally don’t have to be built, and there are new options like converting the biogas to transportation fuel (that may help make co-digesting cost positive).”


Digested material from the digesters, now called biosolids, is made up mostly of organic materials. These are then land applied after a quick trip through a dewatering unit called a centrifuge.

A pilot demonstration project called CANDO – Coupled Aerobic-anoxic Nitrous Decomposition Operation, which was developed by Dr. Yaniv Scherson of Stanford University, “is a new treatment process that removes and recovers energy from ammonia nitrogen sidestreams, specifically the centrate [water leaving a centrifuge] from sludge dewatering devices such as from centrifuges,” said public information manager Angela Lowrey.

The recovered gas is called nitrous oxide – yes, the same gas you’d expect to see in the latest Fast and Furious movie to propel cars to unbelievable speeds. When it comes to generating power however, it can be slipped in with methane gas to produce more power in a cogeneration engine.

“A lot of processes use the anammox bacteria to convert ammonia to nitrogen gas,” Amanda Roa, environmental compliance engineer, told Treatment Plant Operator magazine. “CANDO adds a twist by converting ammonia to nitrous oxide. The pilot will determine how much ammonia can be removed and how much nitrous oxide can be recovered.”

Funding for the project comes from the TomKat Center for Sustainable Energy at Stanford, as well as from the National Science Foundation’s Engineering Research Center for Reinventing the Nation’s Urban Water Infrastructure (ReNUWIt) and grants from the National Science Foundation and Veolia Water.

Delta Diablo is part of a regional coalition made up of 19 agencies across the San Francisco Bay Area called Bay Area Biosolids to Energy (BAB2E). This coalition strives to “create a local sustainable solution to biosolids management by utilizing the remaining energy” in biosolids, according to its website. Just because the organic material has already gasified doesn’t mean it should be discarded at a landfill. Unfortunately, there are increasingly restrictive regulations on what can be used with the biosolids.


When it comes to recycled water projects in the western United States, look no further than the Western Recycled Water Coalition (WRWC). Since its inception, Delta Diablo has been the lead agency behind this group of 24 agencies in California, Washington, New Mexico and Hawaii, representing over 4 million people.

WRWC has successfully secured $38 million in federal funding to construct eight projects and prepare feasibility studies for 14 other projects. For 2016 alone, there are 34 projects in the pipeline totaling $1.5 billion in project cost but creating 197,350 acre feet (243.4 million cubic meters) of water. A list of those projects is available here.

There is a lot that goes into being a water resource recovery leader. Delta Diablo has exemplified that through sharing what they’ve done with RecycledH2O. If you’re in the area, I encourage you to tour their facility to learn about the awesome things they are doing to advance the industry.

This story first appeared on Recycled H2O.

The views expressed in this article belong to the author and do not necessarily reflect the editorial policy of Water Deeply.

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