Research Paper: PMdPower and Machinery Performance and backwashing efficiency of disc and screen filters in microirrigation systems M. Duran-Ros a , J. Puig-Bargue ´s a, *, G. Arbat a , J. Barraga ´n b , F. Ramı´rez de Cartagena a a Department of Chemical and Agricultural Engineering and Technology, University of Girona, Campus Montilivi s/n, 17071 Girona, Spain b Department of Agricultural and Forestry Engineering, University of Lleida, Avda. Rovira Roure 177, 25198 Lleida, Spain article info Article history: Received 27 October 2008 Received in revised form 22 January 2009 Accepted 30 January 2009 Published online 26 February 2009 The performance of three filtration systems (screen, disc and a combination of screen and disc filters) used in microirrigation systems and their automatic backwashing efficiency were studied at inlet pressures of 300 and 500 kPa. The filters were used for more than 900 h with a biological effluent. The physical parameters of the effluent such as turbidity, total suspended solids (TSS) and number of particles were not affected significantly by the different filtration systems at both pressures. Automatic backwashings were classified as being inefficient depending on the value of the initial head loss across the filter after a backwashing took place. The number of filter backwashings required for the screen filter was reduced at 500 kPa, especially due to an increase in efficient backwashings at this inlet pressure. Filtered volume was significantly larger at the beginning of the experiment than after 800 operation hours. The disc filter at both 300 and 500 kPa consumed more water for backwashing than the other filtration systems. ª 2009 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction Effluents are used in agriculture as a viable alternative to freshwater in areas where water is scarce or there is strong competition for its use. Although microirrigation is the most advantageous irrigation system for applying effluents, espe- cially from public health and environmental points of view, the use of effluents can increase emitter clogging (Bucks et al., 1979), which affects water distribution and, consequently, crop yields (Tajrishy et al., 1994). As a result, filtration is an essential operation that can prevent emitters from becoming clogged (Oron et al., 1979), although it does not avoid it completely (Tajrishy et al., 1994). The three common filter types used in microirrigation systems are screen, disc and sand media filters. In screen filters, particles are trapped on the surface of a perforated cylinder. Disc filters have many grooved discs pressed together, and the particles are retained in the grooves of the discs. In media filters, solids are caught by the particles of gravel or sand. In screen and disc filters, the particles larger than the pores of the filtering media are retained on the surface of the media and accumulate layer by layer, forming a cake of increasing thickness that reduces the diameter of pores and allows smaller particles to be retained. In sand filters, the particles to be removed can be smaller than the filter pores since particle capture is controlled by both phys- ical and chemical mechanisms (Adin and Alon, 1986). Screen and disc filters are simple, economical, and easy to manage but sand filters are more complex and expensive, and are only appropriate for farms with high technical and professional standards. Sand filters are also more suitable for waters with high suspended solids content, but disc filters, if * Corresponding author. E-mail address: jaume.puig@udg.edu (J. Puig-Bargue ´ s). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/issn/15375110 1537-5110/$ – see front matter ª 2009 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2009.01.017 biosystems engineering 103 (2009) 35–42