Development of Warp Knitted-Based Filtration Media

Abstract

Biological wastewater treatment based on the removal of various nitrogen forms using activated sludge is a highly efficient and economical method with environmental benefits. The activated sludge comprises bacteria that form colonies on solid carriers (e.g., the most commonly used carrier, AnoxKaldnes). The initial concept behind designing a warp knitted fabric structure (i.e., spacer fabric) with holes is based on the appearance similarity of a three-dimensional fabric and a solid carrier, focusing on potential industrial production. In this study, the longitudinal textile properties of multi- and monofilament materials are measured. A structural analysis is conducted to produce samples unraveled and separated by mono and multifilaments. Density, weight, loop length, filament consumption, specific surface area, and effective area are calculated. Through a basic experiment in a laboratory nitrification reactor, a biofilm is formed on the carriers. The analysis results of the O2 consumption rate of individual design variants reveals minimal differences after 6 and 14 weeks. The efficient carrier area on the outer and inner front and back sides of four developed carrier variants is measured after cutting the monofilaments with the image analysis support. This study might be helpful in designing other textile-based carriers. The warp knitted carrier presented herein demonstrates the capture and presence of an active biofilm evidenced by a higher oxygen consumption rate of up to 8 mg/L/h in 6 weeks. It also shows the benefit of commercially available warp knitted carrier manufacturing.