A Scrolling Geotextile Fabric Filter Device for Primary Clarification

Abstract

This study investigated the feasibility of using a portable geotextile fabric based filtering device to remove suspended solids from raw sewage. This device was considered to replace a conventional primary clarifier. The proposed filtration process directs wastewater influent through a geotextile fabric filter. As filtering progresses, and solids accumulate on the fabric, the loaded fabric is scrolled to present a fresh surface.

Only non-woven polypropylene geotextile fabrics were investigated. These products are constructed by spunbonding or needle-punch technique. Needle-punched fabrics proved superior in terms of Total Suspended Solids (TSS) filtering performance and fabric usage rates. Spunbonded products absorbed less moisture, reducing loaded fabric weight. Fabric thickness did not affect filtration efficiencies for either type of geotextile.

Process variables affecting unit performance were investigated. Flow rate, head level, and fabric tension did not affect TSS removal. Fabric tension, however, is limited by tensile strength of the geotextile material.

Two wastewater receving basin configurations for the device were investigated. An influent basin with two 450 angled walls forming a V-shape performed better in terms of fabric feed rates. It is recommended for full-scale applications.

Finally, several methods were used in an effort to improve treatment performance. Polymer use, and polymer use in conjunction with pre-screening of wastewater, were both used. Polymer use alone did not increase the operating efficiency. Polymer use, along with pre-screening, was promising enough to consider this as a stand-alone treatment system.