Request the Study: “Disinfection in Post-Lagoon SAGR Processes”
A Canadian wastewater treatment innovation has revealed itself to be more capable than previously thought, information that may have come at an important time for many of Canada’s small towns.
“The SAGR has been a technology of choice for cold climate post-lagoon nitrification (ammonia removal) for well over a decade,” says Dr. Damian Kruk. “Although the treatment system was not specifically designed for disinfection, a recent study involving six unique wastewater treatment plants indicated very low E. coli counts in the effluent”.
Kruk has a Ph.D in Civil Engineering from the University of Manitoba. He is also a Senior Applications Engineer with Nexom, the Canadian-based company who pioneered the fully aerated submerged gravel bed technology known as SAGR. The SAGR has been shown to fully remove ammonia from lagoon effluent at more than 60 treatment plants across North America, even in water below 1°C.
“In our recent study, we observed 94% of samples were below the common compliance limit of 100 MPN/100mL,” Kruk explains, adding that a total of 403 discrete effluent samples were collected from the six locations, with the seasonal distribution of the samples being relatively uniform. Kruk adds, “this is even more remarkable when you consider the overall simplicity of a SAGR system.”
How the study worked
The study involved six independent wastewater treatment plants who had E. coli monitoring data as part of the regular testing of their SAGR effluent. These included four Canadian sites (Balcarres, Saskatchewan; Brights Grove, Ontario; Glencoe, Ontario; and Sundridge, Ontario) as well as two US-based sites (Kingsley and Walker, both in Iowa). All six are active municipal wastewater treatment plants involving either facultative or aerated lagoons, followed by a SAGR.
The study was triggered by initial data analysis collected as part of Nexom’s regular follow-up and monitoring of existing SAGR plants to ensure continued compliance with regulations. As Kruk notes, “the study contains data generated over a period of 5 years, with each data set encompassing at least one full year of sampling specifically for the purposes of this study.”
The first six months of operation for each plant were excluded as a start-up condition, but no other data points were removed from the analysis. While some plants do have UV disinfection installed downstream of the SAGR, in these cases, only the values for the effluent directly from the SAGR were included in the study.
A total of 403 discrete effluent E. Coli samples were collected from the six locations, with the seasonal distribution of the samples being relatively uniform. Of the 403 unique samples, only 22 were over the disinfection limit of 125 MPN/100 mL. “That’s a 94% compliance rate with E. coli limits, across six different treatment plants,” says Kruk, adding, “Which is even more remarkable when you consider the overall simplicity of a SAGR system.”
Public and Regulatory Pressure on E. coli
E. coli (Escherichia coli) is a common bacteria found in the digestive system of humans and animals. The presence of the organism itself isn’t usually cause for concern, but the manifestation of E. coli is often an indicator of more harmful microbes, including Cryptosporidium, Giardia, Shigella, and norovirus. Common side effects of contact with contaminated water are stomach cramps, diarrhea, nausea, vomiting, and low-grade fever, but other effects include gastrointestinal illness, skin, ear, respiratory, eye, neurologic, and wound infections.
Canada’s strict Wastewater Systems Effluent Regulations (WSER) have already been in place for ammonia in water discharged into public waterways since 2012. Historically, lagoon based WWTPs have relied solely on natural disinfection via long exposure to sunlight. But with disinfection monitoring requirements now in place, they are often facing higher costs on municipal budgets already stretched tight to meet other nutrient removal limits.
Public awareness and anxiety about the presence of various bacteria, specifically E. coli, has increased dramatically, as news outlets regularly announce product recalls on everything from flour to meat products. The same occurs with public waterways, resulting in the closing of swimming areas and fishing locales.
“With greater public concern, comes a greater need for governing bodies to respond”, says Kruk, who has spent his career working in the wastewater industry and has seen the evolution on how municipalities and companies deal with their nutrient limits.
The best performance result came via the Glencoe SAGR, which recorded a maximum E. coli level of just 16 MPN/100 mL during the period for which data was available. The SAGR system was monitored specifically for E. coli for 15 months with weekly sampling as part of the study. “Glencoe’s system not only outperformed expectations, but of the 61 unique samples taken, 87% of them were also under the detection limit of 2 MPN/100 mL,” says Kruk. “That’s pretty impressive.”
The results from this study is welcome news for wastewater treatment plans needing to address non-compliant E. coli levels in their effluent. The high disinfection capabilities of the SAGR are being increasingly recognized by regulators in both Canada and the US, and the performance results have already benefitted several additional locations, enabling the WWTP to avoid the additional costs to install a disinfection system.
Susan Rennie is the Content Marketing Coordinator for Nexom, based in Winnipeg.
This article was edited November 20, 2019.