Enhanced treatment dramatically improves water quality in the Santa Cruz River
The U.S. Environmental Protection Agency (EPA) recently celebrated the completion of the newly upgraded Nogales International Wastewater Treatment Plant, located in Rio Rico, Ariz., near the border with Mexico.
The facility, upgraded at a cost of $66 million, is now capable of meeting all required permit limits for the 15 million gal per day of wastewater it discharges to the Santa Cruz River.
“We’re celebrating completion of this project which dramatically improves water quality in the Santa Cruz River. Local citizens have already noticed the difference,” said Alexis Strauss, water division director for EPA’s Pacific Southwest Region. “Over the past several years, many partners worked tirelessly to overcome extraordinary obstacles and complete this upgrade.”
Joining the EPA to celebrate the completion of this binational effort were representatives of the cities of Nogales, Ariz., and Nogales, Sonora, the U.S. and Mexican Sections of the International Boundary and Water Commission (IBWC), the Governor of Arizona’s office, Senator Jon Kyl’s office, Representative Raul Grijalva’s office, and the Arizona Department of Environmental Quality.
The facility, which is co-owned by the City of Nogales, Ariz. and the IBWC, has been using an aerated lagoon system since 1991 to treat the sewage from the more than 200,000 residents of Nogales, Ariz., and Nogales Sonora. The lagoon technology was not capable of eliminating toxic ammonia compounds or meeting state permit limits for suspended solids. The facility’s discharge was affecting the Santa Cruz River, home to the endangered Gila topminnow.
In 2000, a federal consent decree required the City of Nogales and the IBWC to improve effluent quality and meet discharge permit limits. A team of state, federal and University of Arizona engineers helped the plant’s co-owners develop and implement a technically feasible, cost-effective solution. The newly upgraded facility, using a conventional activated sludge process with nitrogen treatment, discharges treated wastewater to the Santa Cruz River with lower concentrations of organic and ammonia compounds and significantly improved clarity.