Unintentional phosphate precipitation at water resource recovery facilities (WRRFs) causes operation and maintenance challenges. With global phosphorus (P) scarcity looming and receiving water eutrophication caused by excess discharges of P, intentional P recovery at WRRFs has been gaining traction. To date, struvite recovery as slow release fertilizer has been the focus of P recovery. However, struvite recovery is not always the most cost-effective approach, especially when phosphate fertilizers cost considerably less than the cost to recover struvite as fertilizer. The aim of this state-of-an-art review paper is to discuss P recovery as calcium phosphate, which could be a fertilizer feedstock and incurs less chemical costs to produce. Calcium phosphate also offers broader applications for other industrial uses beyond fertilizers since the composition is close to mined phosphate rock. A strategic approach for a regional reclaimed phosphate reserve is proposed to secure the most economical future supply of P.

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A protocol to select nutrient removal technologies that can achieve low nutrient effluents (total nitrogen (TN) < 5 mg/L and total phosphorus (TP) < 0.5 mg/L) was developed for different wastewater treatment plant (WWTP) sizes based on the research conducted during a Water Environment Research Foundation funded project. The adaptable protocol includes technology and cost assessment of feasible (pre-screened) nutrient removal technologies that are being successfully implemented at full scale. The information collected from the full scale nutrient removal plants to develop this protocol includes design, operational, performance, and cost data through a direct survey of plants, and published data. The protocol includes a "technology threshold" approach consisting of Tier I (TN < 5.0 mg/L; TP < 0.5 mg/L) and Tier II (TN < 3.0 mg/L; TP < 0.1 mg/L) effluent nutrient levels for different plant sizes. A very large WWTP (1,250,000 m(3)/day flow) in Chicago, Illinois, USA adapted this protocol for master planning and design of future nutrient removal facilities based on plant and site specific criteria.

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Wastewater treatment plants in Illinois are exploring different nutrient removal technologies for future plant expansions because of the potential for future NPDES permits with limits on effluent nitrogen and phosphorus. During a master planning project for the North Side Water Reclamation Plant (NSWRP) of the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC), a 333 MGD wastewater treatment plant located in Skokie Illinois, a "technology threshold" approach was used to screen a wide range of nutrient removal technologies into a short-list of five to six proven technologies for large wastewater treatment plants. In order to select a technology from the short list, GPS-X process modelling was used. This paper will present the process of evaluating and selecting nutrient removal technologies at the NSWRP.