Towards a Renewable Future: Assessing Resource Recovery as a Viable Treatment Alternative: State of the Science and Market Assessment

Extractive nutrient recovery, defined as the production of chemical nutrient products devoid of significant organic matter, represents a complementary strategy for managing nutrients in multiple waste streams. In this option, energy and resources are used to accumulate and produce a chemical nutrient product that is recyclable and has a resale value that could potentially help offset operating costs while reducing nutrient production from raw materials for agricultural or other uses. These products include a variety of nitrogen, phosphorus, and iron compounds; however, products like phosphorus-enriched biosolids are excluded from this current report.

This report represents the state of the science review of extractive nutrient recovery technologies with a special emphasis on bridging the knowledge gap currently faced by utilities when considering nutrient recovery for nutrient management. A complementary interactive electronic technology summary matrix is also available. Based on the review of technology, it is proposed that extractive nutrient recovery will likely be most viable if employed within a three-step framework including accumulation, release, and extraction steps.

At the time of this report (2015), phosphorus recovery in the form of struvite was the most established technology for facilitating extractive nutrient recovery at full-scale water resource recovery facilities (WRRFs). Nitrogen only recovery is also feasible but has not been implemented extensively at WRRFs. Taking this into account, it is estimated that the domestic wastewater treatment industry can optimistically bring between 100,000 and 210,000 metric tonnes of P2O5/yr (as struvite) and up to 220,000 metric tonnes N/yr to the fertilizer market. Using historical market data, this suggests that the wastewater treatment industry can optimistically meet between 2 and 5% of the total P2O5 fertilizer demand, between 30 and 100% of the specialty ornamental P2O5 fertilizer demand, up to 2% of the total N fertilizer demand, and between 30 and 194% of the specialty and ornamental N fertilizer demand. The corresponding estimated market price for the nutrient products (2012 U.S. dollars) is approximately U.S.$1.25 to 2.50 /kg of N and U.S.$5.80 to 7.50/kg of P.

Strategies that could be used facilitate the implementation of struvite recovery and other extractive nutrient recovery technologies are provided. These strategies include performing a complete benefits analysis. This analysis should quantify reductions in supplemental carbon requirements, reduction in aeration requirements, reduction in biosolids production for nutrient recovery versus conventional alternative, reduction in costs associated with mitigating nuisance precipitate formation, impacts to sludge dewaterability, and benefits associated with manipulating the N and P content of the biosolids.