May 2008, Vol. 20, No.5
Recycling Nutrients Into Environmentally Safe Commercial Fertilizer
Problem: Meet nutrient removal goals while reducing expenses.
Solution: Struvite recovery process.
The city of Edmonton, Alberta’s Gold Bar wastewater treatment plant recently met a milestone by successfully operating for more than 6 months as the world’s first industrial-size nutrient treatment facility to remove phosphorus and other nutrients from municipal biosolids and recycle them into environmentally safe commercial fertilizer.
Located on 19.5 ha of land in the North Saskatchewan River Valley, the Gold Bar wastewater treatment plant handles wastewater requirements for more than 700,000 people in the greater Edmonton area. The Gold Bar site is also home to the Edmonton Waste Management Centre of Excellence, a research facility specializing in technology demonstration, research facilitation, and operator training for the solid waste and wastewater industries.
The technology, developed by Ostara Nutrient Recovery Technologies Inc. (Vancouver, British Columbia), assisted Gold Bar in achieving its goals of nutrient removal, increasing plant capacity, and reducing maintenance costs while also creating a revenue-producing product in the form of a high-value fertilizer.
Phillip Abrary, president and CEO of Ostara, explained that many wastewater treatment plants, such as Gold Bar, remove phosphorus and other pollutants from wastewater to reduce their nutrient loading on the receiving water environment. When the biosolids are dewatered, the nutrient-rich liquid left in the recycle stream can clog pipes with struvite, a concretelike scale. The result of phosphorus and ammonia (nitrogen) combining with magnesium, struvite can occupy up to 25% to 50% of the system’s capacity, Abrary said.
The Ostara process works by treating the recycled liquids. A proprietary fluidized-bed reactor recovers these fluids in the form of a slow-release fertilizer known as Crystal Green™.
Vince Corkery, director of wastewater treatment at Gold Bar, said that the reactor, which was commissioned last spring, “has extracted more than 80% of the phosphorus on average — achieving the design objective of 75%, and 10% to 15% of the ammonia from a flow of 500,000 liters per day — approximately 20% of the Gold Bar plant’s liquid biosolids stream.”
Crystal Green has a formulation of nitrogen, phosphorus, and magnesium. It dissolves slowly over a 9-month period, making it environmentally safe, as it does not leach into the water table. It works well for parks, golf courses, container nurseries, specialty agriculture, and other markets that value slow-release fertilizers.
The Ostara reactor at Gold Bar produces approximately 500 kg of Crystal Green per day. The product is sorted, dried, and bagged onsite and is immediately ready for commercial sale. No further processing is required, although for some applications, fertilizer distributors may wish to blend it with other fertilizer components to match the agronomic needs of the crop.
As part of the commercial marketing campaign, 23-kg (50-lb) and 1-Mg samples of Gold Bar’s production of Crystal Green are being sent to large fertilizer distributors that will conduct large nursery trials. Commercial sales are expected to commence later this year.
For more information, see www.ostara.com
, or call (604) 408-6697. Vince Corkery can be reached at (780) 496-4322.