A Simplified Transfer Function for Estimating Saturated Hydraulic Conductivity of Porous Drainage Filters Eriona Canga & Bo Vangsø Iversen & Charlotte Kjaergaard Received: 17 July 2013 /Accepted: 22 October 2013 /Published online: 29 November 2013 # Springer Science+Business Media Dordrecht 2013 Abstract Knowledge of the saturated hydraulic con- ductivity (K sat ) of porous filters used in water treatment technologies is important for optimizing the retention of nutrients and pollutants. This parameter determines the hydraulic capacity, which together with the chemical properties of the filter media, affects the treatment per- formance of the filter system. However, measuring K sat is time consuming and expensive. This study developed a novel transfer function to predict K sat of coarse porous media from easily measured parameters. The hydro- physical parameters determined were K sat , grain size distribution, bulk density, uniformity coefficient, parti- cle density, and porosity of 46 porous media fractions. The fractions ranged in grain size from 0.5 to 20 mm and were obtained from seven commercial available coarse filter materials. A backward stepwise regression analysis was performed between K sat and 10 variables obtained from the grain size distribution and bulk den- sity. The optimal model for predicting K sat contained two parameters, D 20 and D 50 , which describe respec- tively the particle diameters, where 20 and 50 % of all particles are finer by weight. The predicted K sat values were in good agreement with the measured values (R 2 =0.91). The transfer function can find potential us- age in relation to dimensioning of permeable agricultural drainage filters or subsurface-flow con- structed wetlands. The predicted values of K sat can also be used as input to numerical models that simulate filter treatment performance. Keywords Saturated hydraulic conductivity . Predictive function . Porous filter material . Grain size distribution . Water treatment technology List of symbols D x Grain size diameter, where x % of all particles are finer by weight U C Coefficient of uniformity, U C =D 60 /D 10 K sat Saturated hydraulic conductivity A Cross-sectional area q Darcy Flux Q Water discharge L Length of the column filter ΔH Hydraulic head n Number of replicates N Number of data (fractions) ρ b Dry bulk density ρ s Particle (solid) density θ tot Total porosity 1 Introduction Porous media are used as filters that physically or bio- geochemically retain nutrients and pollutants present in wastewater from different sources. Water treatment technologies that use porous media as a bed filter are Water Air Soil Pollut (2014) 225:1794 DOI 10.1007/s11270-013-1794-8 E. Canga (*) : B. V. Iversen : C. Kjaergaard Department of Agroecology, Aarhus University, Blichers Allé 20, P.O. Box 50, 8830 Tjele, Denmark e-mail: eriona.canga@agrsci.dk E. Canga e-mail: eriona_canga@yahoo.it