Renewable phosphate fertiliser from sewage: a UK first

Sept. 28, 2010 - PRLog -- A state-of-the-art nutrient recovery facility will remove struvite, a compound containing phosphorus and ammonia, from sewage at Slough sewage works in Berkshire and turn it into premium-grade, slow-release fertiliser.

If left untreated struvite settles as scale on the inside of sewage pipes and valves, narrowing them like furred arteries, increasing pumping and maintenance costs, and in some cases blocking pipes completely. The new plant will solve this problem.

The £2m Slough project, a partnership between Thames Water and Ostara Nutrient Recovery Technologies, is timely because mineable reserves of phosphorus are running out - down to 6% in North America, 1% in Russia and 39% in China - and experts predict these non-sustainable stocks will last only for about another 30 years. Mining the nutrient is also very carbon-intensive.

The phosphorous extracted from Slough wastewater, a sustainable source, forms crystalline pellets which can be spread as fertiliser on crops, lawns, and gardens. The nutrient recovery facility will be built by Ostara, a company based in Vancouver, Canada, whose slow-release fertiliser, Crystal Green, is sold in America and has just received Environment Agency approval for sale in the UK.

Lord Peter Melchett, Policy Director at the Soil Association, said:

"Along with sun and rain, all of our fruit, vegetables and other food need phosphate and nitrogen to grow. For more than 50 years, we have mined phosphate, mainly from North Africa as we have none in the UK, but supplies are running out.

"We must learn to recycle all the phosphate in wastewater to have secure food supplies in future, and this initiative by Thames Water and Ostara is a significant step in the right direction."

The new facility will also help Thames Water meet environmental regulations on nutrient levels in the treated effluent which is recycled back to the environment after leaving the works.

Sewage sludge at the Slough works is particularly rich in struvite because of the high-strength organic waste from nearby businesses. This is a particular problem but it also means Slough is an ideal place for struvite recovery.

When operational in the middle of 2011, the nutrient recovery plant will yield 150 tonnes a year of high-value fertiliser and will save Thames Water £130,000 to £200,000 a year in chemical dosing, which is the traditional method of ridding the plant of struvite build-up.

Slough is not the first place to experience this headache: struvite is also known to have scaled the waste pipes of the Ancient Greeks as far back as 300BC.

Dr Piers Clark, Director of Asset Management at Thames Water, said:

"This project is a classic win:win - we solve a costly problem and in so doing provide a renewable source of phosphate, a nutrient in increasingly short supply, in a convenient and slow-release form, which will please gardeners and golf course green keepers, and help to protect our local waterways.

"We constantly recycle our product, water, back to the environment from which we first borrow it. We are always looking to make use of local, renewable options and this marks the start of an exciting new chapter. The experience gained at Slough will help establish the feasibility of installing the process elsewhere."

Phillip Abrary, Ostara's Chief Executive, said:

"Our new facility will be a model for sustainable innovation in the UK. Ostara's Nutrient Recovery Process integrates directly into Slough's treatment system, processes the sludge liquids, and recovers a high-quality, environmentally-friendly fertiliser that generates revenue for the water company. There is also no risk to Thames Water from a financial or technical perspective.

"Several hundred plants in Europe are potential candidates for the technology, which provides a solution to any sewage treatment works faced with high phosphate concentrations in their (sewage) sludge systems."

Robert F Kennedy Jr, board member at Ostara and leading US environmentalist, said:

"This partnership between Thames Water and Ostara provides a cost-effective solution that benefits the environment at all stages, and truly exhibits the shift that we are seeing towards closed-loop sustainable technologies."