Durham Advanced Wastewater Treatment Plant - Struvite Recovery Project
Clean Water Services is operating the first commercial phosphorus recovery facility in the United States at the Durham Advanced Wastewater Treatment Plant. This plant is producing approximately 40 tons per month of the struvite product Crystal Green™ fertilizer.
HDR provided final mechanical layout design services for Ostara Nutrient Recovery Technologies. Ostara is the company in Vancouver, British Columbia, which helps wastewater treatment systems turn sewage sludge liquids into the Crystal Green™ fertilizer that provides parks, golf courses, commercial nurseries, and specialty agricultural markets with a unique fertilizer that is produced without greenhouse gas emissions.
This three-reactor facility at the Durham facility began operations in May 2009. After the struvite is generated, it is sold as slow-release fertilizer.
The process utilizes a fluidized bed reactor (FBR) to grow struvite crystals. The reactor produces crystal pellets anywhere from 0.5 to 5 mm in diameter. The pellet size can be adjusted to meet individual market needs.
Following the initial startup seeding process, the operation becomes self-seeding, which means no external seeds have to be provided. The size is controlled by the rate of reaction and crystal retention time.
In addition to phosphorus recovery, the process offers additional benefits to the Durham AWWTP ABN facility, including:
- Reduction of recycled phosphorus load
- An increase in biological phosphorus removal reliability
- Reduction of struvite formation potential in the digester and dewatering centrate return system
- Reduction of chemicals needed for supplemental chemical phosphorus removal and alkalinity
- Associated sludge handling and disposal costs
Depending on the direct cost savings and the actual revenue generated by selling the product, the return on investment can be as little as five years.