Dewatering with Geotube® Containers; A Good Fit for a Midwest Wastewater Facility?

Abstract

Wastewater treatment facilities across the Midwest typically operate at > 80% capacity and run out of biosolids/sludge storage capacity when land application contractors (if applicable), drying beds, storage lagoons, and tanks are unable to keep up with volume demands. Several mechanical dewatering options (e.g., belt filter press, centrifuge, etc.) are available as short-term or long-term remedies but are capital intensive for facilities already operating on a tight budget. The objective of this study was to evaluate Geotube® containers as a biosolids dewatering option for a wastewater treatment facility including cost effectiveness, ease of operation, solids retention, solids handling time, flow and volume rates, seasonality, and footprint required to operate. Geotube® containers, with the aid of dewatering polymers, were recommended to and implemented by a wastewater treatment facility into which biosolids were pumped directly from an above ground liquids storage tank. After inline flocculation, the permeable geotextile that forms the Geotube® container allows efficient dewatering while containing the fine grain solids. Overall, this dewatering methodology greatly reduced the volume and mass of residual solids and costs associated with hauling and disposal while allowing continual operation of the facility. For containment and dewatering of biosolids, this Geotube® project (including dewatering polymer and feed equipment) cost less than $0.03/gallon, required minimal technical assistance to install and operate, retained >95% solids, solids were only handled once they were dried sufficiently for hauling and disposal (18 to 40% cake solids), did not interfere with plant operations, and the lay-down area was 6,050 ft 2 . Compared to the previous biosolids management technique (i.e., belt filter press), this Geotube® project saved the facility nearly $25,000 after the first year of operations.