City opens nutrient recovery plant
The City of Saskatoon and Ostara Nutrient Recovery Technologies Inc. have opened Canada’s first commercial nutrient recovery facility at the city’s Wastewater Treatment Plant.
The project is the first commercial plant of its kind in Canada to use Ostara’s Pearl nutrient recovery process to recover phosphorus and nitrogen from the facility’s waste water stream and transform them into Crystal Green, a slow-release and environmentally responsible enhanced efficiency fertilizer.
“The example of responsible stewardship of our resources begins at home,” said Mayor Donald Atchison in a news release, noting that with the project, “we are proactively and cost-effectively tackling the growing issue of nutrient overload in our regional waterways. And that’s good for taxpayers and good for the environment.”
By removing potentially-polluting nutrients from the treatment facility’s waste water stream, the technology helps the city meet nutrient discharge limits and overcome operational issues caused by the unintentional buildup of struvite scale in plant equipment.
Struvite is a concrete-like mineral deposit that chokes process equipment, increases operating and maintenance costs, and undermines plant reliability. The formation of struvite is a common challenge in plants that practice biological nutrient removal and anaerobic digestion.
In Saskatoon, the sludge is handled at a bio-solid facility which is 12 kilometres away from the treatment plant where it is stored. The struvite challenges are exacerbated as the sludge must travel this distance through pipes from the treatment plant to this facility, and then pump decant water back to the treatment plant. Keeping the pipes clear of struvite is a significant operational challenge, especially in the winter. Chemical additives can sometimes be used to mitigate struvite problems, however they are costly and result in a higher volume of sludge waste requiring disposal.
The Ostara system will help the city overcome these challenges by recovering 75 per cent of the phosphorus and 10 per cent of the nitrogen from the waste water stream before they accumulate in the equipment.