Parametros

Aquacultural Engineering 24 (2001) 289– 299
www.elsevier.nl/locate/aqua-online

Determining design parameters for recovery of
aquaculture wastewater using sand beds
G.L. Palacios, M.B. Timmons *
Department of Biological and En6ironmental Engineering, Cornell Uni6ersity, Riley Robb Hall, Ithaca,
NY 14853 -5701, USA
Received 10 October 2000; accepted 31 March 2001

Abstract
Designinformation for the use of sand beds to remove suspended solids from wastewater
discharged from recirculating aquaculture systems (RAS) was developed. Wastewater from a
commercial RAS tilapia farm with 2% total solids and 1.6% total suspended solids (TSS) was
applied to sand columns to determine infiltration rates and phosphorus capture. Various
hydraulic loading rates and drying periods betweenapplication events were evaluated.
Infiltration 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 columns, creating the primary
resistance to infiltration. Concrete sand removed approximately 93% of the soluble phosphorous in the wastewater and wollastonite, an economical aggregate alternative to sand,
removedat least 98%. A modified Darcy equation is presented to predict infiltration based
upon TSS and the number of sequential applications. © 2001 Elsevier Science B.V. All rights
reserved.
Keywords: Infiltration; Sand bed; Tilapia; Manure; Phosphorus; Solids; Darcy equation

1. Introduction
Water and land availability constraints have created a growing interest in
recirculating systems inaquaculture. In order to maximize efficiency and be truly
site-independent, recirculating aquaculture systems (RAS) are being designed to
discharge as little water as possible each day. Currently, many of these facilities
* Corresponding author. Tel.: + 1-607-2551630; fax: + 1-607-2554080.
E -mail address: mbt3@cornell.edu (M.B. Timmons).
0144-8609/01/$ - see front matter © 2001 Elsevier Science B.V.All rights reserved.
PII: S0144-8609(01)00070-X

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G.L. Palacios, M.B. Timmons / Aquacultural Engineering 24 (2001) 289 – 299

replace less than 10% per day of the total water in the system (Kristiansen and
Cripps, 1996; Twarowska et al., 1997). One way to reduce water loss from a
recirculating aquaculture facility would be to reclaim this effluent discharge after
the suspended solidshave been removed.
Handling wastewater is a major problem in all animal agriculture systems, but
there are substantial differences between aquaculture wastewater and manure from
hog or dairy systems. The latter are typically in the range of 5 – 15% suspended
solids, while fish wastewater can be anywhere from 0.2 to 4.0% suspended solids
(Bergheim et al., 1993; Kristiansen and Cripps, 1996;Twarowska et al., 1997).
Typical suspended solids concentrations from drum filters used in intensive aquaculture operations are around 0.5% (personal communication, Mr. Glenn Snapp,
Water Management Technologies, Baton Rouge, LA). Waste production from
aquaculture systems will be from 0.2 to 0.5 kg of waste per kg of feed fed (Drennan
et al., 1995; Chen et al., 1997); thus, water usage rates canbe quickly estimated
from RAS.
Suspended solids are captured in a variety of ways, but primarily rely on
straining, settling or a combination of these techniques (Drennan et al., 1995).
These systems are reasonably effective for removing suspended solids from the
culture water, but rely on periodic flushing of the device to maintain removal
efficiency between flushings. Flushing waters must bereplaced with clean or new
makeup water.
Sand beds have been used in a variety of ways to treat wastewaters. Since the
footprint of a sand bed will be inversely proportional to its hydraulic conductivity,
ways to increase hydraulic conductivity are also common. Using coarse sands and
aggregates with subsurface drainage to remove infiltrate to prevent water accumulation will increase or...