California approves lavatory-to-faucet water recycling

'Water? Like out of the toilet?' It will get cleaned first and it'll be better than Brawndo

Taking a cue from water-starved environments like Arrakis in Frank Herbert's Dune books and the International Space Station, arid California is shortening the distance between wastewater and drinking water.

On Tuesday the US state, which experienced some drought relief in 2023, approved rules that allow treated wastewater to be added directly into the public water system, rather than requiring it to pass through an intermediary aquifer, reservoir, or groundwater source.

The five members of California's State Water Resources Control Board voted unanimously to adopt the rule change [PDF].

The rules govern Direct Potable Reuse – which is when municipal wastewater is cleaned and placed into a public water distribution system or a water supply that's immediately upstream of the system's water treatment plant.

Indirect Potable Reuse is when treated wastewater gets injected into the ground to replenish the groundwater basin – as is done with the Orange County Water District's Groundwater Replenishment System.

For decades, California has recycled treated wastewater as a non-potable resource – in toilets and urinals, in fountains, for firefighting, and for making artificial snow at ski resorts, among other uses.

But in light of governor Gavin Newsom's 2022 Water Supply Strategy – enacted to mitigate water shortages due to various factors such as climate change, drought, population growth, and groundwater overuse – the state aims to reuse more of the treated wastewater previously released into the Pacific Ocean. Now some of that reclaimed liquid, at the discretion of water utility operators, can head to tap in a less circuitous route.

A significant amount of water usage can be attributed to the technology industry. According to a recent UC Riverside study, AI software is a heavy drinker – consuming 17 ounces for every 20 to 50 ChatGPT queries.

The study observes that Microsoft's US datacenters burned through about 700,000 liters of water in the roughly two weeks of training required by GPT-3 and that the AI industry and supporting datacenters are expected to use far more water in the years ahead.

"[T]he global AI demand may be accountable for 4.2 to 6.6 billion cubic meters of water withdrawal in 2027 – which is more than the total annual water withdrawal of 4–6 Denmarks or half of the United Kingdom," the study observes. "This is very concerning, as freshwater scarcity has become one of the most pressing challenges shared by all of us in the wake of the rapidly growing population, depleting water resources, and aging water infrastructures."

And of course datacenters handle other workloads beyond training and running AI models. Google last year revealed that in 2021, its global fleet of datacenters consumed about 4.3 billion gallons of water. Meta is estimated to have consumed 2.57 million cubic meters of water (~679 million gallons) during 2021 – an increase of 16.67 percent over the previous year, according to Global Data.

The WateReuse Association, a trade association focused on promoting water recycling, sees the new rules giving communities more flexibility to take advantage of a tried and tested water source.

"These new regulations are a tremendous step forward as we develop Pure Water Southern California, which will be one of the largest recycled water facilities in the world and benefit 19 million people in our service area,” declared Deven Upadhyay, executive officer of the Metropolitan Water District of Southern California and vice president of the WateReuse Association, in a statement.

"Pursuing direct potable reuse for a portion of the supplies produced at our Pure Water facility will allow us to better manage the weather extremes we face from a changing climate. We applaud the state board for developing this new resource, while making public health the top priority." ®

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