Extracting liquid fertilizer from ammonia-laden pharmaceutical wastewater using Hollow fiber membrane contactors

Abstract

Production of certain pharmaceuticals generates wastewater with a high ammonia load, posing economic and environmental burdens. Recovering ammonia as a nitrogen fertilizer can alleviate these burdens and is vital from a circular economy perspective. For this purpose, this study, jointly performed by a research university and a large pharma company, evaluated the use of Hollow fiber membrane contactors (HFMC). The experiments were conducted using real pharmaceutical wastewater in two separate laboratories at two process scales (bench and pilot) and two operating modes (batch and continuous). The study evaluated the effect of feed concentration, flow rate, and process configuration and described the results using a single-parameter (mass transfer coefficient K) mathematical model. We then used the model to design scaled-up batch and continuous processes, based on which we performed a detailed economic assessment. A robust and consistent ammonia removal and recovery were obtained for all the experimental conditions tested. The model adequately described the empirical results, and K was similar across all the experiments in this study, which were conducted in practically relevant conditions. Both batch and continuous process designs were found feasible, increasing process flexibility. The economic evaluation revealed that acid and base consumption, rather than the initial investment, is the most significant expense. The cost of membranes, although relatively high, had little contribution to the overall expenses. Revenues from selling the recovered nitrogen as ammonium-sulfate fertilizer reduces the evaluated net cost of the novel treatment to a minimum of $3.76 per kgN - a potential cost savings of up to 29% relative to the current treatment ($5.28). Therefore, applying HFMC to recover nitrogen from pharmaceutical wastewater is promising from both economic and environmental viewpoints.