Techno-economic analysis of resource recovery technologies for wastewater treatment plants

The high nutrient content of domestic wastewater can be efficiently recovered through specific technologies included in dedicated wastewater treatment plants (WWTPs). Nevertheless, the operational costs linked to the implementation of these technologies can make them economically unfeasible. It is therefore important to evaluate the best way to upgrade an already existing WWTP from an economic point of view. In the present work, this is virtually done by using a simulation model, namely the Benchmark Simulation Model n°2 (BSM2), as base case study. The BSM2 is extended by including the following resource-recovery treatment units: (a) a chemical precipitation process, for recovery of iron phosphate fertilizer; (b) the Exelys technology, for increased biogas production; and, (c) the Phosnix technology, for recovery of struvite fertilizer. Seven upgrade strategies/flowsheets employing different combinations of the recovery technologies are generated and evaluated. The evaluation results have shown that the most economically beneficial strategy to upgrade the WWTP is to employ a Phosnix reactor in the side-stream to recover phosphorus from the bottom of the dewatering treatment unit. All other upgrading combinations involving chemical precipitation and Exelys technologies were not found economical for the given plant. Sensitivity analyses on the economic evaluation criteria have demonstrated that the results obtained are robust against uncertainties in influent wastewater characteristics and technical (e.g. recovery yield) performance parameters.