LOS ANGELES – The Metropolitan Water District of Southern California is in talks with Los Angeles County sanitation districts about developing what could be one of the largest recycled water programs in the world.
In a committee meeting Monday, the agency’s staff presented the framework of a plan to purify and reuse as much as 168,000 acre-feet of water a year – enough to serve about twice that number of households for a year.
Doing so would require MWD to build a treatment plant and delivery facilities and comply with various environmental regulations. Officials say similar projects have cost about $1 billion.
It would also signal a shift for the region’s water titan away from the business of importing water from elsewhere and toward developing local supply.
“I’m not afraid of talking about another business model,” said Board Chairman Randy Record. “None of us should be.”
Currently, coastal communities in California flush hundreds of billions of gallons of treated sewage into the Pacific Ocean each year. In the last couple of decades, however, water managers have attempted to recycle some of this water for human use.
So-called purple pipe systems take sewage that has been filtered and cleansed and use it to irrigate crops, parks and golf courses. This water, however, is not used as drinking water.
Potable reuse systems, on the other hand, use a variety of methods to purify water that has already been processed at a sewage treatment facility. The end result of this “toilet to tap” process is a substance that is cleaner than most bottled waters, and is intended for human consumption.
Recycled potable water can either be added to municipal water systems directly or indirectly. In an indirect potable reuse system, such as the Orange County Groundwater Replenishment System, purified water is placed in an “environmental buffer,” such as an underground aquifer or surface water reservoir. After a period of storage, the water undergoes processing at a traditional drinking water treatment plant and enters the tap system.
As drought places increasing strain on traditional sources of drinking water, water managers have looked to expand water recycling systems and thereby increase local water supply.
In the city of Los Angeles, Mayor Eric Garcetti has directed the Department of Water and Power to reduce its purchase of imported potable water by 50% by 2024. He has also called for the creation of an “integrated water strategy that increases local water supplies and that improves water security.”
Officials in Orange County say their Groundwater Replenishment System — which can treat up to 100 million gallons per day – will eventually be able to purify 130 million gallons a day for reuse. They say it is the largest such system in the world.
MWD officials hope that in about a decade, their treatment plant will produce 150 million gallons per day, eclipsing their neighbors to the south.
“Met has always been very supportive of water recycling,” said MWD Assistant General Manager Debra Man in an interview. “This takes it to the next level.”
MWD and a partnership of two dozen county wastewater purveyors – known as Sanitation Districts of Los Angeles County – have been working together on feasibility reports and pilot studies since 2010, according to informational documents on the recycling project. MWD officials said they want the board to authorize a memorandum of understanding between the two groups as early as November.
If the board gives its OK, the agencies could launch on a “demonstration project” at the sanitation districts’ Joint Water Pollution Control Plant in Carson in about 20 months. There, the treatment processes would be perfected on 1 million gallons of water per day while officials conduct additional studies and develop a financing plan, according to an MWD memo.
Man told board members the demonstration phase would cost about $15 million. In an interview, she said it was not clear where the funding would come from, though MWD officials have said it is possible that some of the costs may be covered by a water bond passed by voters last year.