Determining design parameters for recovery of aquaculture wastewater usingsand beds

Design information for the use of sand beds to remove suspended solids from wastewater discharged from recirculating aquaculture systems (RAS) was dev eloped. Wastewater from a commercial RAS tilapia farm with 2% total solids and 1.6% total suspended solids (TSS) was applied to sand columns to determ ine infiltration rates and phosphorus capture. Various hydraulic loading ra tes and drying periods between application events were evaluated. Infiltrat ion rates stabilized after five application events to 3.5 cm/day (S.D. = 1. 7). Practically, all suspended solids were captured at the top of the colum ns, creating the primary resistance to infiltration. Concrete sand removed approximately 93% of the soluble phosphorous in the wastewater and wollasto nite, an economical aggregate alternative to sand, removed at least 98%. A modified Darcy equation is presented to predict infiltration based upon TSS and the number of sequential applications. (C) 2001 Elsevier Science B.V. All rights reserved.