Los Alisos Pumps (copy)

Pumps at the Los Alisos Wastewater Treatment Plant in Nogales, Sonora began malfunctioning in January.

A sewage treatment plant in Nogales, Sonora, whose malfunctioning pumps resulted in the flow of contaminants across the border and into Santa Cruz County earlier this year, is still struggling to reach 50 percent of its wastewater processing capacity as Mexican authorities try to repair and replace faulty equipment.

With only two of its five water pumps partly working, the Los Alisos Wastewater Treatment Plant is currently able to process a maximum of 220 liters of water per second – well below its full power of 400 liters, an official said.

However, according to agricultural engineer José de Jesús Quintanar Guadarrama of Mexico’s International Boundary and Water Commission, also known as CILA, the facility isn’t even meeting the reduced capacity.

“There’s some equipment that’s damaged and some equipment that is sort of functioning, so right now we’re sending 180 liters per second with that,” Quintanar said during a meeting of the U.S. International Boundary and Water Commission (USIBWC) Southeast Arizona Citizens Forum last Thursday evening at Nogales City Hall.

In January, the Arizona Department of Environmental Quality announced that raw sewage was flowing north through the Nogales Wash on the U.S. side of the border after four of five water pumps at Los Alisos stopped working due to excessive grit buildup. In late July, a spokeswoman for the USIBWC said the agency was not aware of any “fugitive flows” in the wash related to the pumping problem.

Quintanar noted last Thursday that while the wastewater at the plant passes through a sand remover before reaching the pumps, officials didn’t realize the amount of sand that was still reaching the processing facility.

He explained that the Chimenea Wash, which flows along Avenida Tecnológico on the west side of Nogales, Sonora, connects with the sanitation system and eventually feeds directly into the Los Alisos facility.

“The sand was reaching us directly and it wasn’t only in the sand remover, but it would flow over to the pumping area,” Quintanar said about the damages at the plant.

He added that ADEQ provided funding to repair two of the broken pumps, one of which has already been reinstalled and is in working condition.

As for the remaining broken equipment, he said, CILA was able to secure funding from the Mexican federal government for two new water pumps, which they expect to receive in November.

“The population is growing, so our (wastewater) volume is also increasing,” Quintanar said of the challenges faced by the city. “That’s why we’re working to accelerate the work at Los Alisos, so that those spillovers don’t affect” the Nogales International Wastewater Treatment Plant in Rio Rico, which processes runoff from the Nogales Wash, as well as wastewater from Nogales, Sonora sent north through a cross-border pipeline known as the IOI.

Quintanar, who spoke to forum members through an interpreter, did not provide a clear answer to their questions about what Nogales, Sonora is doing with any wastewater that can’t be treated at the under-performing Los Alisos plant.

Water contaminants

In addition to hearing the Los Alisos status report last Thursday, members of the USIBWC Southeast Arizona Citizens Forum also contemplated new types of contaminants that have been found in waters around the world, including Arizona cities.

Professor Mark Brusseau of the University of Arizona explained that ADEQ conducted a study of contaminants known as per- and poly-fluoroalkyl substances last November, and found high levels in Tucson and Prescott. However, it wasn’t clear if any studies had been conducted in the Nogales area.

“These are what we call emerging contaminants, so that means that right now they are not regulated,” Brusseau said.

He explained that military bases and fire departments release the highest volumes of these contaminants into the environment. They’re also found in consumer products such as detergent, food wrappers and stain-proofing products.

He continued that while research on the contaminants, also known as PFAS and PFOS, is very limited, it has already been linked to health risks such as affecting children’s growth and learning development, increases in cholesterol levels and increases in the risk of cancer.

And while the contaminants aren’t federally regulated and can be very difficult to destroy, he said, some filtering techniques can remove the substances from drinking water, such as those that use granular-activated carbon or resin beads.

The members of the citizens forum, which is meant to serve as an intermediary between the USIBWC and the public about commission projects and issues in Southeast Arizona, voted to ask ADEQ whether any studies have already been conducted in the Nogales area, and to further ask the agency to test local waters in order to move forward in addressing the issue – if the contaminants are present.

“If those pollutants are present in this area, which nobody knows if they are right now, they can be treated with conventional wastewater treatment, which neither plant is equipped to do,” forum chair John Light said of the two treatment plants in Ambos Nogales. “And since (the contaminants) currently aren’t regulated, it might be difficult to find funding.”

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