San Diego’s Unusual Water Recycling Program

Posted in: Drinking Water News, Drought, United States Water News
Tags: , , ,

Water is pumped through microfiltration membrane filtration modules (tubes) at the Advanced Water Purification Facility in University City at the city of San Diego’s North City Water Reclamation Plant, the first step to making the water comparable as pure distilled water in quality. (Photo Credit: Howard Lipin)

Article courtesy of David Garrick | July 11, 2015 | The San Diego Union Tribune | Shared as educational material

— San Diego’s $3.5 billion plan to fight the drought by recycling sewage into drinking water is forcing state regulators to rewrite their water recycling rule book.

State rules call for purified sewer water to be pumped into large natural basins under ground before it can enter the local water supply, partly because that’s how it’s done where water recycling essentially began in Orange County.

San Diego’s lack of adequate groundwater basins and aquifers, however, will force local officials to pump the recycled water directly into city reservoirs.

That nearly unprecedented approach, which will shrink the amount of time between water getting recycled and showing up in faucets, could create health concerns and make it harder for the public to embrace recycled water, which some critics call “toilet to tap.”

But it could also make San Diego a model for the many other drought-stricken cities in the West that lack ground water basins but still see recycling sewer water as their best option.

San Diego’s proposal has prompted state officials to begin crafting proposed regulations for pumping purified sewer water into reservoirs instead of into ground water, with a first draft of those regulations slated for release in late summer.

“Since there aren’t any regulations for doing this with reservoirs, we’re working hand-in-hand with the state to develop them,” said John Helminski, assistant director of the city’s Public Utilities Department. “There isn’t a precedent for how this works.”

San Diego needs state approval to move forward with its water purification program, which is expected to produce 83 million gallons a day of potable water by 2035 — a third of the city’s needed supply.

Helminski said he’s optimistic the state will approve San Diego’s use of the large San Vicente Reservoir by the end of 2016, but that approval for using smaller reservoirs, such as Lake Miramar or the Alvarado reservoir in La Mesa, will be trickier and isn’t expected until early 2018 at the earliest.

“From the feedback we’ve gotten so far, they feel we are taking the right approach,” said Helminski, adding that San Diego has conducted more than 9,000 tests and had outside doctors and scientists verify results. “They’re happy with the research and the outcomes and that we have an independent panel to help vet all this information.”

Randy Bernard, recycled water unit chief for the state’s Division of Drinking Water, said he’s also optimistic San Diego’s use of reservoirs will get approved.

“The technologies that they’re implementing and the methods that they’re using are right in line with what we feel are safe for public health,” Bernard said.

While using ground water has a track record, Bernard said there’s nothing magical about that approach that makes it superior to using a reservoir.

“The public health protections are equivalent,” he said.

The key to either approach is creating a buffer of some kind between the recycling of the water and it showing up in faucets, which officials call “retention time.” That time allows the recycled water to mix with imported water and rain, and also creates an opportunity for regulators to step in if something goes wrong during purification.

“When Orange County injects their water into the ground up in Anaheim, it takes nearly six months for it flow down to the Huntington Beach area where it’s drawn out,” Helminski said.

In contrast, retention time in San Diego will be much shorter because the distance is much less between the northern and southern ends of the San Vicente Reservoir.

That will force San Diego to purify the water more aggressively than the typical process, which includes micro-filtration, reverse osmosis and the use of ultraviolet light and hydrogen peroxide.

In addition to those efforts, Helminski said San Diego will seek to eliminate pharmaceuticals by treating the water before purification. That approach could be particularly crucial in getting approval for San Diego’s smaller reservoirs, where retention time would be even less.

While reservoirs can be as effective as basins, Bernard said San Diego’s approach might make it harder to convince the public to embrace drinking purified sewer water.

“Studies show that when people fully understand it the ‘yuck factor’ dies way down, but there’s a bigger disconnect when it goes in the ground,” he said. “Once you see it coming from the ground you forget where it came from, but in a reservoir there’s still that little connection because you see where it comes in and goes out.”

Bernard and Helminski said San Diego would likely become a model for many other cities and water agencies exploring water recycling.

But Bernard said most such cities plan to use Orange County’s ground water model if possible.

He also said San Diego might not be an ideal model because most other communities lack reservoirs as large as San Vicente.

“It’s huge and it’s got great retention time,” he said. “Other reservoirs around the state just don’t have the same capacity.”

The city plans to eventually have three water recycling plants.

One would be at the North City Reclamation Plant near Miramar Road, where a pilot project has been under way for several years. It’s slated to produce 15 million gallons of water per day by 2023.

The second facility, slated to begin producing another 15 million gallons by 2027, would be an expansion of the South Bay Wastewater Treatment Plant near the international border.

The third plant is tentatively slated to open by 2035 somewhere on Harbor Drive. It would produce an additional 53 million gallons per day.

Want to Donate?
Please contact us for gifts in kind - Mail your check to: P.O. Box 545934, Surfside, Fl 33154