PRE-FILTRATION IN BOULDER AND SLOW SAND FILTRATION WITH NON-WOVEN SYNTHETIC LAYERS AND GRANULATED VEGETAL COAL TO IMPROVE QUALITY IN WASTEWATER TREATED BY CONSTRUCTED WETLANDS

The objective of this study was the comparison between two filtration systems, being one composed of a boulder pre-filter followed by a slow filter with sand as filtration media and a non-woven synthetic fabric in the upper part, and the other one composed of a boulder pre-filter followed by a slow filter with sand as filtration media and granular activated charcoal and a non-woven synthetic fabric in the upper part, for the purification of household effluents treated in cultivated beds, to be applied in fertigation. The filtration systems were compared to assess the efficiency in the removal of the parameters: suspended solids, turbidity, apparent color, chemical oxygen demand, dissolved oxygen, iron, manganese, total coliforms and E. coli. The two systems operated 24 hours a day, with the same application rate, treating a total final flow of 1.5 m(3) day(-1), while the application rate for the pre-filtration unit was 8.4 m(3) m(-2) day(-1) on average and for each of the slow filtration units it was 2.7 m(3) m(-2) day(-1) on average. The pre-filtration and slow filtration units were efficient in the reduction of suspended solids concentrations, turbidity, apparent color and COD, for the purification of previously treated domestic sewage. The use of granular activated charcoal combined with sand in the slow filter allowed a higher efficiency in the removal of suspended solids, color, turbidity, total coliforms and E. Coli., without increasing the initial head loss. The use of effluents is possible in the fertigation practice, where the disinfection process may be necessary or not, depending on the cultivation and the irrigation system adopted.31480381

Effect of waterfalls and the flood pulse on the structure of fish assemblages of the middle Xingu River in the eastern Amazon basin

Abstract The structure of fish assemblages in Neotropical rivers is influenced by a series of environmental, spatial and/or temporal factors, given that different species will occupy the habitats that present the most favourable conditions to their survival. The present study aims to identify the principal factors responsible for the structuring of the fish assemblages found in the middle Xingu River, examining the influence of environmental, spatial, and temporal factors, in addition to the presence of natural barriers (waterfalls). For this, data were collected every three months between July 2012 and April 2013, using gillnets of different sizes and meshes. In addition to biotic data, 17 environmental variables were measured. A total of 8,485 fish specimens were collected during the study, representing 188 species. Total dissolved solids, conductivity, total suspended matter, and dissolved oxygen concentrations were the variables that had the greatest influence on the characteristics of the fish fauna of the middle Xingu. Only the barriers and hydrological periods played a significant deterministic role, resulting in both longitudinal and lateral gradients. This emphasizes the role of the connectivity of the different habitats found within the study area in the structuring of its fish assemblages

Baited remote underwater video as a promising nondestructive tool to assess fish assemblages in clearwater Amazonian rivers: Testing the effect of bait and habitat type

Baited remote underwater video (BRUV) systems are being used in marine ecosystems as a nonextractive, cost-effective method of assessing the fish fauna with minimal species bias. This technique has had limited applications in freshwater ecosystems. Rheophilic fish assemblages of the Xingu River, a clearwater Amazonian river in Northern Brazil, were sampled with BRUV systems. Two-hour video recordings were collected using five different bait treatments (sardine, croaker, cat food, sweet corn, and no bait) in two lotic habitat categories (rocky and sandy bottoms). A total of 2460 fish from 56 taxa and 13 families were recorded from the 80 BRUV deployments. Significantly different fish assemblages, species richness, and abundance were detected between habitat types and among treatments. Our results suggest that the use of crushed sardines as a standardized bait optimizes the sampling recording the highest species richness, relative abundance, and number of exclusive species of rheophilic fish in clearwater Amazonian rivers. The data also highlight the unique fish diversity of the Xingu River prior to the expected large-scale environmental degradation resulting from the forthcoming operation of the Belo Monte hydroelectric power plant