Efficacy of Pilot-Scale Wastewater Treatment upon a Commercial Recirculating Aquaculture Facility Effluent - Aquaculture and the Environment: A Shared Destiny - page 141

8
Efficacy of Pilot-Scale
Wastewater Treatment upon a Commercial
Recirculating Aquaculture Facility Effluent
Simonel Sandu 1 , Brian Brazil 2,3 and Eric Hallerman 1
1 Virginia Polytechnic Institute and State University
2 U.S. Department of Agriculture - Agricultural Research Service
3 Geosyntec Consultants, N.W., Kennesaw, GA
USA
1. Introduction
Recirculating aquaculture systems have been developed to produce high-value species for
year-round supply of markets, to free production from site-related constraints, to minimize
environmental impacts of aquaculture, and to make efficient use of limited high-quality
water supplies. Effective treatment and reuse of aquaculture effluent has been demonstrated
at an experimental scale. Blue Ridge Aquaculture (BRA, Martinsville, Virginia, USA) is a
commercial venture producing 1360 metric tons of hybrid tilapia ( Oreochromis sp.) per year
in recirculating aquaculture systems. To our knowledge, BRA is the largest recirculating
aquaculture enterprise under one roof in existence. Increased production at BRA is
constrained by the availability of high-quality influent water. Meanwhile, BRA discharges
an estimated 2290 m 3 of wastewater per day to the municipal sewer system, equivalent to an
average of 1 m 3 discharged per 3.0 kg feed. Importantly, discharge of this effluent also loses
heat energy, as water temperature is maintained at about 28 - 30ºC to optimize tilapia
growth. Concerned about the reliability and costs of their wells and the city water system,
BRA seeks a technical solution. Developing a wastewater treatment system that recovers
and reuses the water presently discharged could minimize these problems. The discharge
issues faced by BRA typify intensive aquaculture, and evaluation of possible treatment
strategies would have general interest to the aquaculture sector.
The BRA waste stream was characterized over eight-hour sampling periods during 12
different days. The results indicated that solids, chemical oxygen demand (COD), and
nitrate were the most significant waste components by concentration and weight. All these
forms of pollutants were targeted by unit processes in a treatment train. Following an ozone
treatability study (Sandu, 2004), a pilot-scale wastewater treatment station was built in order
to initiate, characterize and optimize the operation of this more complex treatment strategy.
The ultimate goal was to obtain an effluent clean enough to be reused in the recirculating
systems. The need to eliminate settable solids, colloids, dissolved organic substances and
nitrogenous compounds led to selection of a sequential treatment process employing
physical, biological, chemical, and again, biological steps. The performance of the pilot-scale
wastewater treatment train with regard to solids and carbonaceous compounds was