ENVIRONMETRICS Environmetrics 2003; 14: 743–759 (DOI: 10.1002/env.618) Statistical sensitivity analysis of packed column reactors for contaminated wastewater A. Fasso ` 1, * ,y , A. Esposito 2 , E. Porcu 3 , A. P. Reverberi 2 and F. Veglio ` 4 1 Department of Engineering, University of Bergamo, Italy 2 Department of Chemical and Process Engineering ‘G.B. Bonino’, University of Genova, Italy 3 Department of Quantitative Methods, University of Milano Bicocca, Italy 4 University of L’Aquila, Italy SUMMARY In this article we consider the statistical sensitivity analysis of heavy metal biosorption in contaminated wastewater packed column reactors. In particular, the model describes the biosorption phenomenon using the Advection Dispersion Reaction equation under rapid local equilibrium. This allows computer simulation with random input parameters chosen from appropriate probability distributions. In order to have a statistical framework for analyzing the simulated data and assessing input importance, we introduce heteroskedastic and multivariate sensitivity analysis, which extends standard sensitivity analysis. Copyright # 2003 John Wiley & Sons, Ltd. key words: multivariate SA; heteroskedastic SA; heavy metals biosorption 1. INTRODUCTION Heavy metals are toxic pollutants released into the environment by industrial, mining and agricultural activities. Due to non-biodegradability of these pollutants, environmental risk increases as accumula- tion and concentration take place. The main treatments used to remove heavy metals from wastewaters are precipitation, ion exchange and reverse osmosis. The application of such processes is often limited because of technical and/or economic constraints. For example, precipitation, which is used as a preliminary process, does not guarantee the metal concentration limits required by regulatory standards. Moreover, it produces wastes which are difficult to be disposed. On the other hand ion exchange and adsorption processes are very effective but need expensive adsorbent materials and difficult plant management (Volesky, 2001). There are two main reasons for considering biosorption in wastewater treatment. The first is good performance in metal removal, often comparable with reverse osmosis. The second is low cost and availability in nature of adsorbent bio-material (Volesky, 2001). Received 15 July 2002 Copyright # 2003 John Wiley & Sons, Ltd. Accepted 29 January 2003 *Correspondence to: A. Fasso `, Department IGI, via Marconi 5, 24044 Dalmine BG, Italy. y E-mail: fasso@unibg.it