Nutrients recovery from treated secondary mainstream in an urban wastewater treatment plant: A financial assessment case study

Abstract

This study presents the financial assessment for implementing an ammonium and phosphate simultaneous recovery process based on the use of calcium activated synthetic zeolites in a large urban Waste Water Treatment Plant (WWTP) located in the Metropolitan Area of Barcelona.A calcium activated synthetic zeolites was selected, after a benchmarking analysis, as it reported capability for simultaneously recover ammonium and phosphate by a combined mechanism of ion exchange for ammonium and formation of insoluble mineral phase for phosphate. The loaded sorbent, rich in ammonium and phosphate, can be used as slow-release fertilizer.Financial indexes such as the net present value, the internal return rate, the return of investment and the payback period were calculated concluding that the integration of a zeolite-based sorption treatment stage in the main stream is economically feasible, with a reasonable payback period. The need, to achieve low-levels of P and N on the discharged waters and the need to develop more sustainable WWTP facilities indicate that the deployment of nutrient recovery solutions will be encouraged. The sensitivity analysis carried out to define the critical parameters of the economic performance of the technology allows concluding that the main variable in the viability of the nutrient recovery unit is related to the nutrients sorbent, both in the cost of purchase and in the market for the sorbent loaded with nutrients.