Canadian Technology Removes Phosphates From Sewage

Unsightly green algae floating upon lakes and waterways is an ongoing problem around the world, and it is exacerbated by the release of phosphates from sewage treatment plants.

A new Canadian technology might have the answer. Dr. Donald Mavinic, P. Eng., who heads up the University of British Columbia’s environmental program, presented the patented PEARL technology before a group of Parliamentarians and others in Ottawa last fall.

The technology removes up to 90 per cent of the phosphorous as well as ammonia from the liquid sewage sludge stream. It involves an upflow fluidized bed reactor that has a roughly 30-m2 footprint. Magnesium is added to precipitate a chemical reaction, producing phosphoros pellets that can be harvested. The pellets are pure, slow release fertilizer in granular form that can be sold commercially and used for nurseries and other specialized crops.

Not only does the fertilizer provide a source of revenue, but also the process reduces the formation of struvite scale on plant equipment. Struvite scale can be as hard as concrete and must be removed from pipes, pumps and valves either using chisels or jackhammers, or by the application of strong chemicals.

By recycling the phosphorus, the technology saves mining a non-renewable resource. “The world is running out of phosphate rocks,” Mavinic points out.

Also, by capturing the phosphates from effluent, the technology stops them entering waterways.

Mavinic’s team at UBC developed the Pearl technology over 10 years. It is patented by UBC and licensed to Ostara, a Vancouver-based company. Ostara has one full-scale operating plant in Portland, Oregon that opened last year, and two more are under construction in the U.S.

So far the only plant in Canada is in Edmonton; EPCOR has an Ostara demonstration plant outside the city and will add five more units in 2012 to make it full-scale.