Rafters and anglers can thank upgrades at the Santa Rita Water Reclamation Facility for a safer and healthier Animas River.

A study by Mountain Studies Institute, the city of Durango and the Colorado Department of Public Health and Environment released late last year has revealed that upgrades made to the Santa Rita Water Reclamation Facility from 2017 to 2020 have improved water quality in the Animas River.

The improvements have decreased the nutrients and bacteria the reclamation facility discharges into the Animas River, creating a healthier ecosystem for aquatic life and making the river safer for recreation.

“If you looked at water quality changes as the Animas moves past Santa Rita, in the past you would see an increase in nutrients and bacteria as you went past the effluent (where the facility discharges cleaned water). After the upgrades, that decreased so that the downstream water quality was more similar to the upstream water quality,” said Scott Roberts, an aquatic ecologist and the water programs director for MSI.

In 2014, CDPHE and the state of Colorado gave the city of Durango more than $64 million in low- or no-interest loans to upgrade the reclamation facility south of town. The upgrades were meant to increase the capacity of the facility as Durango grows while also improving the efficacy of its wastewater treatment to meet state water quality standards and align with Regulation 85, which Colorado passed in 2012 to reduce nutrient pollution in rivers and lakes.

The improvements were extensive and included new headworks, which is where the wastewater enters the plant, secondary processing infrastructure and an ultraviolet disinfection system. They completely changed parts of the water treatment process at Santa Rita.

“What we were doing for disinfection previously was chlorinating and then dechlorinating the water, so adding chlorine into the water to do disinfection and then bringing that level of chlorine back down before we discharged the water into the Animas,” said Justin Elkins, Santa Rita Water Reclamation Facility manager for the city of Durango. “What we do now is we use UV light.”

From 2017 to 2020, the city, CDPHE and MSI conducted a study to quantify the water quality improvements in the Animas River from the facility’s upgrades as a part of CDPHE’s Measurable Results Program.

They took water samples above and below Santa Rita, as well as at the point where the facility discharged treated water back into the river, and measured the concentrations of nutrients and E. coli.

The changes were significant.

The study found the upgrades reduced phosphorous by 93%, nitrogen by 59% and E. coli by 90% in the water the treatment plant releases into the Animas.

Santa Rita’s May 2020 permit allowed for 100 mg/L of nitrogen in the water it released. After the improvements, it was releasing 7.16 mg/L.

For E. coli, the facility’s permit allows 1,756 mpn/ml. With the new UV system, it now releases less than 10 mpn/ml, Elkins said. Mpn/ml stands for most probable number per milliliter and is a measurement of the concentration of bacteria in water.

“That should give you an idea of how well we’re doing,” Elkins said.

Those who participated in the study were less sure if they would be able to detect improvements directly in the Animas River, in part because the river has many other sources of pollution, Roberts said.

The study again found significant reductions in phosphorous, nitrogen and E. coli.

Water samples showed a 90% decrease in phosphorous, 58% decrease in nitrogen and 67% decrease in E. coli with less nutrients and bacteria downstream of the facility.

The water quality improvements have significant implications for recreation and the Animas River’s ecosystem.

“The E. coli reduction definitely makes the water safer for recreating (and) for agricultural use downstream,” Elkins said. “Pulling out the nitrogen, phosphorus and E. coli are huge helps to both the aquatic life and other downstream users.”

Rafters and anglers are now at less risk of E. coli infection if they ingest water from the Animas River. Santa Rita’s May 2020 permit shows concentrations of E. coli in treated water from the plant well below limits.

E. coli is usually an indicator of other harmful organisms, such as giardia and cryptosporidium, Elkins said.

For fish and aquatic inspections, the reduction in nutrients has myriad benefits, the first of which is improving habitat.

Nitrogen and phosphorous spur the growth of algae. When algae grows on rocks and other surfaces on the bottom of the river, it reduces the places where insects and fish at different life stages can live, Roberts said.

Nitrogen and phosphorous can also create algal blooms that take over bodies of water. When algae dies, bacteria decompose it. As they do, they also consume oxygen, which depletes the oxygen in the water for fish and other aquatic life. This process is known as eutrophication and can lead to expansive die-offs and dead zones like those seen in the Gulf of Mexico.

While eutrophication usually happens in more stagnant and warmer water, algae growth in the Animas River helped by nitrogen and phosphorous can still reduce oxygen in the water, affecting fish species such as trout that need more oxygen.

Though eutrophication in the Animas River is not much of a concern now, it could become more of a problem with climate change, Roberts said.

“It’s not a huge problem on the Animas yet, but it could be especially with the more frequent drought conditions that we’re experiencing that are leading to warmer summer temperatures in the river and less water in the river, especially later in the summer,” he said.

The water quality improvements from the upgrades to the Santa Rita Water Reclamation Facility will extend far beyond the few miles of the Animas River immediately below the water treatment plant.

Farther downstream, the Animas River has concentrations of excessive nutrients and bacteria, Roberts said.

“Any kind of reduction we can have on the (river) system could help lessen cumulative impacts downstream,” he said.

Roberts said he hoped the study showed those who live in Durango the tangible water quality improvements made by the upgrades at Santa Rita Water Reclamation Facility, while also raising awareness about water use and the wide-ranging impacts of water quality in Durango.

“What maybe people don’t think about as much is when they flush the toilet in Durango, it’s going to Santa Rita to be treated and now treated at a really high quality,” he said. “That benefit is passed on to downstream users and downstream communities.”

ahannon@durangoherald.com