Project
Textile curved screen - filter system for separating solids from wastewater streams with a low-maintenance cleaning concept based on structured pile textiles with defined separation behavior
Filters for solids separation have long been used successfully in environmental and wastewater technology. However, increasing demands on the planning, operation and maintenance of wastewater treatment plants are leading to a constant need for new, robust and efficient materials.
The cleaning units currently in use, such as curved screens made of welded stainless steel, are often custom-made products with high acquisition and maintenance costs due to the individual requirements.
The aim of this project was to develop a continuous solids separation system for wastewater streams with a low-maintenance cleaning concept based on structured pile textiles with defined separation behaviour.
At the beginning, the requirements for the filter in terms of mechanical load capacity and filter properties were defined. The materials to be used for the textile filter and initial approaches for the design of the textile filter with pile structure were derived from this.
Tufting technology was used to create the pile structure, as it is very variable and economical compared to other textile processes for producing three-dimensional structures. Thermobonding (using a calender) was chosen to consolidate the pile structure. This process ensures the necessary permeability of the primary backing to maintain the filter properties. The textile filters produced with a pile structure were then tested on an adapted test rig with regard to the requirements defined in the project, evaluated and systematically developed further.
In the course of the project, it became apparent that the textile filter constructions did not meet the defined requirements of a continuously moving filter textile and that the high mechanical loads favored the fiber discharge to be avoided. As a result, textile filter constructions for a static filter process were pushed forward and a special focus was placed on tuft bonding through thermobonding (using a calender).
The target groups for this project are users (local authorities, water boards), filter manufacturers and plant constructors as well as companies in the textile value chain (yarn and textile fabric manufacturers).
Results:
As part of the project, the secondary clarification of a wastewater treatment plant was defined as an application for the use of the textile curved screen. The requirements derived from this for the filtration properties of the textile filter constructions, such as the dry residue, were not achieved in the development carried out. One possible reason for this is the restriction of the titer of the man-made fibre yarns used to a single filament titer of > 24 dtex. The reason for this restriction was to minimize the possible introduction of microplastics into the aquatic environment through broken single filaments. Despite this requirement, the fibre discharge was high depending on the tufting construction. However, it was significantly reduced by the further development of the thermal pile nub integration used. One approach to minimizing the potential environmental impact of fibres would be to use biodegradable polymers. With such polymers, breakage of the fibers is less critical due to their better environmental compatibility, so that the use of microfibers would also be possible. In addition, there is a need to simulate the mechanical and hydraulic loads on a laboratory scale in order to advance the development of pile nap integration in line with requirements.
Based on the filtration tests carried out with the manufactured textile filter constructions, the basic influences of the construction parameters such as tuft and filament density can be derived.
The final report on the research project can be obtained from the research institute as TFI publication series no. 2022/121.
Project partners and/or other research institutes
Research Institute for Water Management and Climate Future at RWTH Aachen University (FiW) e. V.
Acknowledgement
The IGF project “Textile curved screen – filter system for solids separation from wastewater streams with low-maintenance cleaning concept based on structured pile textiles with defined separation behavior” 21147 N of the research association Forschungskuratorium Textil e.V., Reinhardtstraße 14 – 16, 10117 Berlin was funded by the Federal Ministry of Economics and Climate Protection as part of the program for the promotion of joint industrial research and development (IGF) on the basis of a resolution of the German Bundestag.