1 Evaluation of MF and UF as pretreatments prior to RO applied to reclaim municipal wastewater for freshwater substitution in a paper mill: a practical experience Ruth Ordóñez a , Daphne Hermosilla a , Ignacio San Pío b and Ángeles Blanco a* a Department of Chemical Engineering, Universidad Complutense de Madrid. Avda. Complutense s/n, 28040 Madrid, SPAIN b Department of Quality and Development, HOLMEN Paper Madrid. C/ del Papel 1, Parque Industrial “La Cantueña”, 28947, Fuenlabrada, Madrid, SPAIN * Corresponding author: Tel.: +34 91 394 4247; fax: +34 91 394 4243. E-mail address: ablanco@quim.ucm.es (A. Blanco)