As a study on the safety of crop irrigation with produced water wraps up, the Cawelo Water District is seeking low-cost treatment technology to enable greater beneficial reuse.
For years, California’s Cawelo Water District (CWD) has used high-quality, minimally treated produced water from the west side of the Kern Valley to irrigate crops for human consumption. The CWD has recently turned its attention to the very poor-quality produced water from the east side of the valley and is preparing to carry out a pilot in Fall 2020 to remove boron salts.
The CWD is the state’s largest user of produced water for irrigation, receiving about 450,000 bbl/d of produced water from Chevron’s Kern River field and California Resources Corporation’s Kern Front field. After the operators perform oil-water separation, that produced water nearly meets drinking water standards. The CWD blends it with surface water at a ratio of about 1:1 before applying it to crops.
“If it’s a really wet year, [that produced water] could be half of our water supply, but in the really dry years, it’s well over half of our water supply,” David Ansolabehere, CWD general manager, told WiO. As California’s water stress rises due to drought, competition for resources and new regulations, the district has become increasingly interested in securing water from other sources.
The produced water from the valley’s east side would necessitate advanced water treatment such as reverse osmosis. That would raise the cost of the water to around $600-800 per acre foot (af), which is on par with surface water prices during dry years, but far above surface water prices during moderate to wet years – around $50-100/af – and the highest prices paid now for high-quality produced water – around $70-80/af.
“We’re looking at the most economical process to make this a feasible project. There’s plenty of water out there, but cleaning it up is a big issue,” Ansolabehere said. He added that the CWD, which relies heavily on water-intensive agriculture, is open to piloting any technology that could improve the economics of treating poor-quality produced water (see contact details below).
California regulators are also moving on beneficial reuse. In July, a panel of experts commissioned by the Central Valley Regional Water Quality Control Board (CVRWQCB) is expected to release a white paper summarizing years of regular reporting and lab analysis of produced water and the crops it has been used to irrigate. The paper will also include recommendations on the continued use of produced water for this purpose.
CVRWQCB assistant executive officer Clay Rodgers told WiO that following a public comment period, the paper will be presented to the board, which will hopefully pass a resolution to accept it. If it does, that could open the doors for greater beneficial reuse.
In Kern County, produced water has been used for around 40 years to irrigate crops such as almonds, pistachios, citrus and grapes. However, in 2015, growing concerns from environmental groups and questions from the CVRWQCB itself led it to assemble a panel including toxicologists and food safety experts to assess the impacts of produced water on food safety.
“We’re not aware of any issues that indicate that the use of this water is not safe, or that it has any discernible impact on fruits, nuts and vegetables, but we’re trying to be vigilant and make sure there isn’t something here that has unintended consequences,” Rodgers explained.
So far, the CVRWQCB has approved five permits allowing a total of 87,000 af of produced water to be discharged annually to about 94,000 acres of land, including in the CWD. In 2019, the actual cumulative discharge was 41,440 af, but growing water scarcity and regulations on groundwater use could see those volumes increase in years to come.
“Hopefully, the technology will continue to evolve to make [produced water treatment] cheaper. Once it gets to a level that is affordable for agriculture, you’ll see a tremendous explosion in the use of produced water,” Ansolabehere predicted.
To get in touch with David Ansolabehere about setting up a potential technology pilot, send an email to firstname.lastname@example.org.