Waste phosphorus recovery a 'win-win'

Even if they choose not to believe it, most people have by now heard scientists’ warnings that we’re pushing the planet’s climate and biodiversity beyond their limits. What many might not realise, however, is that the Earth’s phosphorus cycle could also be in danger of reaching a tipping point.

Some phosphorus enters the planet’s oceans and waterways naturally every year through normal weathering. But society has been dumping far more phosphorus into the environment thanks to its heavy use of fertilisers in agriculture and rising livestock production. Fertiliser- and manure-laden runoff adds a growing amount of phosphorus to waterways, where it can fuel blooms of algae that suck the oxygen out of the water with deadly consequences for marine life.

For example, in China, now one of the world’s largest users of phosphorus-containing fertilisers, runoff from farms is causing significant pollution problems in rivers, lakes and coastal waters. One lake that’s experienced serious eutrophication — oxygen depletion — receives agricultural runoff delivering more than six kilograms of phosphate per hectare, more than six times the amount that would be considered the limit in developed countries.

In addition to creating environmental problems, phosphorus-laden runoff represents a massive waste of resources: not only are the world’s phosphorus reserves dwindling, but the extraction process is very carbon-intensive.

One company that sees a great opportunity in that is Canada’s Ostara Nutrient Recovery Technologies. Built on technology developed at the University of British Columbia and founded in 2005, Ostara helps water treatment plants recover both phosphorus and ammonia from wastewater. The process not only helps treatment facilities meet environmental requirements for nutrient content in discharged water but transforms the captured resources into an eco-friendly commercial fertiliser. It also reduces a persistent problem for sewage treatment plants: buildup of the phosphate mineral struvite that can clog system pipes and lines.

This week, Thames Water’s Slough Sewage Treatment Works in London became the first such facility in the UK to announce it will extract phosphorus from wastewater through a partnership with Ostara. The plant’s nutrient recovery system is expected to be completed and operational by the middle of next year.

“Resource recovery is a key principal underlying Thames Water’s sludge management strategy — this technology fits very well with that principal,” said Piers Clark, asset management director for Thames Water. “The implementation of this innovative technology has the potential to help improve the operational efficiency of our treatment plants, reduce their energy usage and protect water quality — benefits that extend beyond the treatment plant.”

Thames Water will pay a monthly fee to Ostara but will not have to make any capital investment of its own to build and implement the system. In addition to an expected savings of £130,000 to £200,000 a year in chemical costs, Thames Water will also receive revenues from Ostara’s sale of Crystal Green, the fertiliser produced from recovered waste nutrients. Already being sold in North America, Crystal Green is on track to soon being marketed in the UK as well. Ostara says the fertiliser not only “recycles” waste nutrients but is environmentally friendly as it dissolves slowly over six to nine months, rather than leaching into the environment.

The Thames Water facility is eventually expected to yield about 150 tonnes a year of the Ostara fertiliser.

“This project is a classic win-win: we are transforming the problem of excess nutrients into a valuable product, reducing our maintenance costs and helping the environment by producing a fertiliser that will not leach and damage local ecosystems,” Clark said. “The exciting thing is that this product is derived from a renewable source of phosphate, and will be marketed and sold to growers, horticulturists and the turf industry in the UK.”

Phillip Abrary, Ostara’s president and CEO, said many sewage treatment works are effective at removing phosphorus and other pollutants and diverting them into a sludge stream of liquids and solids, but are then left with the problem of disposing of these nutrients, along with the operational challenges created by the buildup of struvite in pipes and equipment. He added that several hundred plants in Europe are potential candidates for the technology.