Sioux Falls, SD (KELO AM) - Sioux Falls Water Reclamation Plant and South Dakota State University work together to solve problems in wastewater treatment.
When wastewater utilities work with universities, it can be a beneficial relationship that can offer the best of both worlds for the two parties. Utilities gain access to young, eager minds; cutting-edge technologies and solutions; and a technical expertise that may not be available at their water resource recovery facility (WRRF).
University researchers can gain hands-on experience, conduct studies, and gather data that can later be used for long-term research projects; and students learn what it’s like to work in the field and gain experience that can help them find positions after graduation. The City of Sioux Falls, S.D., and South Dakota State University (Brookings) have engaged in this type of partnership for decades.
“Sioux Falls has partnered on research projects with South Dakota State University for over 20 years,” said Mark Perry, wastewater superintendent for the City of Sioux Falls. “The university is typically looking for graduate projects and the City of Sioux Falls has had good results in partnering with them.” Using an old technology to solve a problem
South Dakota State has been working at the Sioux Falls Water Reclamation Plant since 2007 when researchers conducted a digester-mixing study, said Christopher G. Schmit, associate professor of Civil and Environmental Engineering at South Dakota State and director of the university’s Water and Environmental Engineering Research Center.
In fact, the university has received $20,000 annually from the WRRF to conduct its research. The funding is included in the WRRF’s capital improvement budget.
The South Dakota State team has done Phase 1 and 2 nutrient removal studies and a filtration study. The team conducted the filtration study in 2010, after the WRRF decided to replace its existing filters that trap solids before treated wastewater is released into the Big Sioux River, according to a South Dakota State news release.
The old filters were dual media filters, made of anthracite and sand, according to the news release.
“They placed them after the final clarifier,” Schmit said. “They were used to meet the permit requirements for organics and suspended solids.” He said these filters also served as an insurance policy in case of failure of other mechanisms upstream, but the filters were starting to experience wear and tear.
“The media had lost its bottoms and was deteriorating,” Schmit said. “It needed to be replaced.”
So researchers decided to install a new filtration system that would increase the flow rate through the filters and automate the backwash system, according to the news release.
Schmit said they considered several replacements, including compressed media, cloth media, and traditional granular media filters. He said they finally settled on filters that were suggested by former Sioux Falls Public Works Director Lyle Johnson. These monomedia filters that use an older technology require less backwash than traditional filters because the particles in the monomedia filters are bigger than normal, Schmit said. “It allows for more pore space and therefore more solids removal before backwash,” he said.
The timeframe for having to backwash the filters was reduced from every 24 hours to every 2 to 3 days, therefore using half as much water and requiring less backwash water to be treated.
This helped the WRRF gain 3028 to 3407 m3/d (800,000 to 900,000 gal/d) of capacity, “because we don’t have to send the water to the head of the plant again,” Perry said in the news release. According to South Dakota State, backwashing the monomedia filters also saves the city approximately $12,000 per year in labor and energy costs.
Schmit said “the downside potentially is that you don’t get as much removal of solids, but since these filters are an insurance policy for the city, this isn’t important.”
In addition, stress tests with high solid levels showed that the WRRF could still achieve 2 or less turbidity units with the monomedia filters, which were still well within permit limits, Schmit said.
“We had a lot more success than we thought we would with this pilot,” Schmit said. Next on the list
Since the filtration study, Schmit said his research team completed a study on grease trap waste to help the Sioux Falls Water Reclamation Plant determine what type of loading would inhibit its anaerobic digester or whether fats, oils, and grease (FOG) would change behavior of the digester.
Schmit said the research team isn’t sure what it will do next at the WRRF. “We ran through the list we had,” he said.
We’ll have to find out what city wants us to do next, he said.