USE AND REUSE OF A GEOTUBE® TO CAPTURE SOLID WASTE IN A FLOWING WATER SYSTEM
In aquaculture systems geotextile membranes are used to capture solid waste and remove BOD. This demonstration was designed to determine whether a Geotube® could be used, emptied, and reused. In this experiment, two Geotube® units (70 m2 ), one new and the other used were evaluated with regard to removal of total solids, total suspended solids, BOD, particle size, and the soluble constituents NH3, NO2, NO3, and PO4. The Geotube® units were used year round periodically receiving effluent obtained by cleaning of quiescent zones in a set of eight raceway units stocked with approximately 2800 kg of trout fed daily. The reused unit had been in service about a year before this demonstration. The seams were cut, collected solids were removed, the material was cleaned with a pressure washer, and the seams were resealed by folding the edges, sandwiching them between two wooden boards and screwing the boards together. Rather than receiving a constant stream of effluent the units alternately received approximately 6000 L of effluent as the quiescent zones in each of the raceways were cleaned on alternate days. Each unit drained fully between uses. The evaluation was conducted over a period of 660 days with samples taken on eight occasions.
Both the new and used units performed equally well removing about 70% of total solids, 93% of total suspended solids, and about 86% of BOD. There were no significant differences in soluble nutrient concentrations between the new and reused units. Soluble nutrient concentrations were elevated over influent indicating that mineralization was occurring within the unit.
This Geotube® product is a heavy material designed for use at high pressure, but was used in a low pressure system. We expect that this product used in this manner will allow depreciation of the $1800 investment over a five year interval. When a unit is removed from service, material inside appeared to have dried and composted yielding an appealing soil amendment. This system has also been labor efficient and requires removal of solid waste only once each year.