Relocating First Nation Town Meant Building a Completely New Wastewater Treatment System
The following article was originally published in Environmental Science & Engineering’s February 2019 issue.
In May 2011, excessive snow melt, frozen soil conditions and spring rainfall at a rate 200% over normal meant the Assiniboine River at Portage La Prairie, Manitoba, would have had to handle 1,690 m3/s of floodwater, the highest on record dating back to the 1890s. As such, the decision was made to use the Portage Diversion to its full capacity, directing more than 980 m3/s of water into Lake Manitoba, the Fairford River, and ultimately Lake St. Martin.
Already at its maximum recommended level of just over 244 m, the extra water increased this by an additional 1.4 m. As a result, the surrounding lowlands flooded, and the 1,400 people that lived in Lake St. Martin First Nation were relocated to Winnipeg.
By the time the waters receded, more than 80% of the Lake St. Martin First Nation’s homes were left unsalvageable, and the town was uninhabitable.
A NEW BEGINNING
In May 2013, it was announced that Lake St. Martin First Nation would be moved from its existing location to an adjacent parcel of land north of the existing reserve, close to original ancestral sites but also elevated an average of 6.10 m above the lake.
“It’s a whole new community, a brand-new community, and it will put Lake St. Martin on the map,” said Chief Adrian Sinclair, when speaking about the agreement to the Winnipeg Free Press in 2014.
The agreement made Lake St. Martin the second-largest reserve in Manitoba and formed a blueprint for the new townsite. This included a new K-12 school and housing, a church, graveyard, daycare centre, community centre, band office and medical centre. Finally, it included the necessary infrastructure required for a new community of now 2,500 people, including a new wastewater treatment plant.
SOLVING THE WASTEWATER ISSUE
The new wastewater treatment system had to meet two key issues. The first was operations and maintenance (O&M), since it can be difficult to find individuals who possess the qualifications needed to run O&M-intensive treatment facilities in remote communities.
Also, should repairs to the facility be required, it is expensive and time-consuming to get the needed parts and expertise on site, particularly where funding is required from the federal government. This meant the new facility needed to be relatively simple to run and easy to maintain.
Secondly, the system needed to meet Canada’s 2012 Wastewater System Effluent Regulations (WSER), which stipulate not only that effluent un-ionized ammonia cannot exceed 1.25 mg/L, but it also cannot be acutely lethal under the Fisheries Act. A study done by the Saskatchewan Water Security Agency found that this consistently occurs at levels as low as 0.2 mg/L.
But, the stakes for the performance of the Lake St Martin wastewater treatment system were higher. Any system installed would be discharging into the lake, so non-compliance might not just mean a fine, but it would poison the water, land and wildlife with which the First Nations peoples have a unique relationship.
At Lake St. Martin, the average low temperature from December to March is below -20°C, a merciless cold that exposes flaws in any number of treatment processes and leaves little margin for error.
In order to take advantage of the low O&M requirements of a lagoon but still produce the effluent quality needed to protect fish and wildlife, while also continuously discharging throughout the winter, the engineers for Lake St. Martin First Nation identified an aerated lagoon followed by a SAGR® attached-growth reactor for cold-water post-lagoon nitrification as their preferred solution.
A SIMPLE SOLUTION
“Simple in maintenance. Simple in operation. Even simple to construct,” says Liliya Chunderova, speaking specifically about the wastewater treatment plant she designed for Northlands Denesuline First Nation. “In extreme cold conditions, like those in northern Manitoba, a facultative lagoon would need a bigger footprint and it still wouldn’t meet WSER requirements. But, an aerated lagoon with a SAGR for nitrification will.”
Chunderova was referencing a made-in-Manitoba innovation created by Nexom, which is being used at 50 locations across North America, with 21 additional systems being installed. It is used to consistently reduce total ammonia-nitrogen (TAN) levels in near-freezing water to levels below 1 mg/L.
The un-ionized ammonia mentioned in WSER is a component of TAN, the proportion of which is related to water temperature and pH.
The SAGR features a clean gravel bed with the influent wastewater’s flow evenly distributed across the width of the cell, to be collected by a horizontal chamber at the end of the treatment zone.
Linear aeration throughout the floor of the system provides aerobic conditions that are required for nitrification. The gravel bed is then covered with a layer of wood chips or mulch for insulation.
The SAGR’s performance met Lake St. Martin’s required criteria. It nurtures the nitrifying bacteria needed to reduce ammonia to <1 mg/L in <1°C water, while polishing BOD and TSS, and can even provide substantial fecal and total coliform removal.
But, of particular importance was the low level of O&M. The only moving parts are the positive-displacement blowers feeding the in-bed aeration. Routine maintenance of the blowers as well as infrequent opening and closing of valves (part of the step-feed process) are the only operational tasks required beyond a rudimentary daily visual inspection. It is estimated that the O&M at Lake St. Martin requires an average of 15 minutes of an operator’s daily time.
“The ease of operating and maintaining a SAGR really sets it apart,” says Ken Mattes, the long-time Manitoba coordinator for an INAC-funded circuit rider program, working with wastewater treatment operations on First Nations. “When you get into Level 3 plants, you need two years of post-secondary education just to operate it. But, with the SAGR, sewage goes into the lagoon and clean effluent comes out with very little effort.”
CONSTRUCTION AND COMMISSIONING
The aerated lagoon and SAGR for Lake St. Martin First Nation were constructed in 2016, engineered by J.R. Cousin Consultants of Winnipeg and built by Penn-Co of Blumenort, Manitoba. First commissioned in late fall, biomass within the bed was established in early spring, and the system entered its first full winter in 2017.
Without the benefit of detailed data from Lake St. Martin, conclusions about its performance can be drawn from similar systems. Located in southwestern Manitoba and spared from the flooding that affected Lake St. Martin, in 2012, Long Plain First Nation built a nearly identical process train to that built later at Lake St. Martin.
This included a green-field two-cell, partial mix aerated lagoon-based system and a SAGR process for BOD, TSS and ammonia removal. This was followed by two vertical flow, continuous backwash sand filters with alum addition for phosphorus removal. Since commissioning, the Long Plain plant has been shown to reduce lagoon effluent ammonia that can peak at 17 mg/L, down to effluent levels averaging 0.15 mg/L.
Merle Kroeker and Susan Rennie are with Nexom.
References are available upon request.