A B S T R AC TThis work addresses the assessment of nanofi ltration (NF) in terms of membrane characteristics, operating transmembrane pressure and feed composition for the maximal removal of anionic surfactants in wastewater from a detergent industry. Model solutions of linear alkylbenzene sulphonates (LAS) and sodium lauryl ether sulphates (SLES) covering a wide range of SLES/LAS ratios are used as surrogates of the wastewaters with 0.43 g l −1 of methylene blue active substances (MSAS). The NF experiments are carried out in a unit equipped with NF-90, NF-200 and NF-270 membranes (FilmTec Corp., USA). The applied pressure varied from 15 to 25 bar. The rejection coeffi cients to total organic carbon (TOC) are practically independent of pressure and are higher than 95% for all model solutions and higher than 92% for the wastewater. The SLES solutions have the highest permeation fl uxes of 20-33, 121-207 and 242-371 kg h −1 m −2 for NF90, NF200 and NF270 membranes, respectively. The permeation fl uxes for the other model solutions have intermediate values between the ones of the SLES solution and the ones of the wastewater. These present permeations fl uxes as low as 10-11 kg h −1 m −2 for the NF 200 and the NF 270 membranes.

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The main goal of the work developed is to present the results from a set of studies conducted in different regions of Portugal where a conceptual model of sludge management was applied. In order to achieve the objective of the use of organic resources on land, all the partnerships (producers, users, authorities, regulators) should be convince that the sludge/biosolid is safe, sustainable, trusted and welcome. The selection of the use/disposal method or management system was based on technical factors such as, local geography, climate, land use, availability or disposal sites and regulatory constrains, giving also emphasis to the local traditions, personnel experience and public opinion. The wide spread of different WWTP by region in study (size, treatment process and local specific parameters) led us to the construction of hypothetical sludge management scenarios. The decision depends on several factors, namely, economical, environmental, logistical, energy recovery and land use. This tool can be used, not only for the region in study, but also for different municipalities, although it should be adapted to the different “municipality specific” and “site specific” parameters. The results were thoroughly analysed to identify parameters that could have a potential influence on the results.