The technical feasibility of using ultratiltration (UF) to treat four types of liquid pig manure from different treatment stages in an experimental farm was studied. The determination of concentration factors and the optimization of operating parameters were conducted in batch mode. A tubular lab-scale UF unit featuring 0.1 m(2) PVDF membrane was used. Optimal operating parameters for transmembrane pressure and recirculation velocity were found to be 100 kPa and 2-2.5 m/s, respectively, for most manure types. The concentration factors reached were about 4.0 L/L. The performance-limiting factor is suggested to be the suspended solids concentration, which could be reduced with better pre-treatment. Operating costs of the UF cell ranged from 1.4 to 8.0 USD/m(3). Tertiary treatment by UF of pig manure appears to be expensive for small farms where the savings due to scale-up factors are not significant. However, for a compact and stable process that can completely remove suspended solids, total coliforms and constitute a good pre-treatment for reverse osmosis, UF appears promising. © 2005 Elsevier B.V. All rights reserved.