This study had as objectives to assess water quality using macroinvertebrate communities in Gaviao artificial reservoir (Brazil), used to supply potable water to 2.5 million people, and to evaluate how these organisms responded to the discharge of water treatment sludge into a natural wetland. A total of 1,621 specimens across 23 taxa were identified. Mollusca were the dominant and most frequent group while Insecta presented the most richness. Based on feeding mode, there were more predator organisms than scrapers. The Biological Monitoring Working Party (BMWP') method showed to be more sensible to water quality variations than ASPT index, going from polluted to questionable water quality more frequently. The chemical parameters analysed showed no significant variations and were not a sensitive method for assessing water quality. No organisms could be found downstream of the sludge discharge point, indicating a high impact of sludge disposal on local biota. Costa et al. 26 T.R. Alves Abreu da

This study had as objectives to assess water quality using macroinvertebrate communities in Gaviao artificial reservoir (Brazil), used to supply potable water to 2.5 million people, and to evaluate how these organisms responded to the discharge of water treatment sludge into a natural wetland. A total of 1,621 specimens across 23 taxa were identified. Mollusca were the dominant and most frequent group while Insecta presented the most richness. Based on feeding mode, there were more predator organisms than scrapers. The Biological Monitoring Working Party (BMWP') method showed to be more sensible to water quality variations than ASPT index, going from polluted to questionable water quality more frequently. The chemical parameters analysed showed no significant variations and were not a sensitive method for assessing water quality. No organisms could be found downstream of the sludge discharge point, indicating a high impact of sludge disposal on local biota. Costa et al. 26 T.R. Alves Abreu da