Sludges generated during purification of water for human consumption are produced in large volumes and have high environmental polluting potential. The sludge dewatering technique using geotextile closed systems has been used to reduce the sludge volume for final disposal. It is a system that allows encapsulation, insulation, dewatering and disposal of sludge, which allows control of the input and output variables of the system. Also known as geotextile tubes, geotextile containers and geotextile bags are a function of their size. This work presents a discussion about the main factors influencing this sludge dewatering technique and its applicability for sludges generated in a water treatment plant. The study includes tests with single filling and with refilling the small geotextile bags in equipment constructed to simulate control of operational conditions, such as flow rate and pumping pressure. The evaluated performance of this system according to parameters proposed in the literature is also presented. The results obtained indicate that the efficiency of the dewatering technique depends on both the characteristics of the sludge and the geotextile properties. This study indicates the importance and efficiency of the dewatering technique in geotextile closed systems in reducing the sludge volume for final disposal.

Maintaining satisfactory properties in geosynthetics exposed to factors that could lead to their degradation needs to be considered in projects employing these materials. Geosynthetics subjected to tensile creep and weathering can undergo premature degradation over time. It is essential to study the influence of these factors, since they could act simultaneously in some applications. To assess the synergetic effects, frames were developed and four groups of a woven geotextile polypropylene sample were tested. The first and second groups were subjected to tensile creep at 5% and 10% of the tensile strength in conjunction with weathering for 2160 h. The third group was exposed to the same weathering conditions without tensile load. The fourth group was subjected to tensile creep at 10% of the tensile strength in laboratory conditions. Frames were built with a slope similar to the location of exposure to guarantee greater effects of weathering on the material surface. A meteorological station at the site monitored the meteorological parameters. The degradation suffered by the geotextile was determined by comparing tensile strength test results. The results presented show the importance of the constructed frames in assesssing tensile creep and weathering in the field under small loads.

The durability of geosynthetics against degradation agents is a relevant issue to be considered for the analysis of their life cycle and relevance to their application. Sunlight, high temperatures, oxygen, environments with acidic or alkaline pH and the presence of water are some of main degradation agents of polymeric materials. The purpose of this study is to evaluate the durability of a polypropylene woven geotextile against some climatic and chemical degradation agents that have been simulated in the laboratory, as well as to analyze the influence of the sum of these agents on the geotextile durability. Reduction factors were also defined for both weathering and chemical degradation, acting both in isolation and as the sum of degradation agents. The results showed that geotextile degradation occurs by both climatic and chemical agents and that the degradation increases with the sum of degradation agents. Furthermore, different results were obtained for the reduction factors with respect to particular conditions of degradation, which are important in defining reduction factors for the specification of geosynthetics based on conditions as similar as possible to that of the site and of the project requests. This study contributes to a better understanding of geotextile durability, which is a subject of considerable relevance in the geotechnical, environmental and scientific fields.

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