Efficacy of Pilot-Scale Wastewater Treatment upon a Commercial Recirculating Aquaculture Facility Effluent - Aquaculture and the Environment: A Shared Destiny - page 156

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. We built and operated a pilot-scale wastewater treatment station at
a large commercial recirculating aquaculture facility in order to evaluate treatment
strategies for effluent recovery and reuse. The treatment train consisted of sedimentation,
denitrification, ozonation, nitrification and chemical flocculation. We report the dynamics of
alkalinity, pH, hardness and nitrogenous compounds through the treatment process.
Alkalinity lost by water exchange was recovered due to nitrification, and alkalinity in
treated effluent was 26-33% higher than initial alkalinity. pH increased from a mean of 7.21
in the initial influent to 7.60 in the final effluent after larger changes through the treatment
train. Hardness decreased by approximately 10%, with the degree of decrease positively
correlated with ozone dose and with associated removal of total suspended solids. Up to
96% of total Kjeldall nitrogen was removed, mostly as organics. Although ammonia was
produced during ozonation, it was partially removed in the trickling filter, decreasing by 35-
40% after treatment. Over 94% of NO 3 - -N was removed by the treatment train, declining to
2.0-2.7 mg/l. The biological yield for denitrification, Y b (g biomass volatile suspended
solids/g NO 3 - -N), was 0.69, and maximum nitrogen removal was 23.4 kg NO 3 - -N /m 3 -day.
The nitrogen removal in the denitrification reactor was between 16 and 23 kg NO 3 - -N /m 3 -
day. Nitrogen removal was higher than generally expected from wastewater treatment, in
part because of the high temperature of operation, 28-30°C. We conclude that the pilot
station design was effective for conserving alkalinity and hardness and for removing
nutrients, and could be scaled up to treat and reuse the entire effluent stream. Should the
system be scaled up, our results predict significant savings in operations costs, largely due
to savings in energy required to heat the exchange water. While the treatability of
aquaculture effluent and cost structure for treatment were specific to BRA, the approach we
took to assess treatability and to evaluate the treatment train are general and will have
applicability to a range of recirculating aquaculture system operations.
5. Acknowledgement
S.S. was supported by a Commercial Fish and Shellfish Technologies grant award to E.H.
and by the Department of Fish and Wildlife Conservation at Virginia Polytechnic Institute
and State University. We are grateful for access to the production facilities at Blue Ridge
Aquaculture and to the water quality laboratory of the Department of Civil and
Environmental Engineering at Virginia Tech University, and for the technical training and
advice of Dr. Nancy Love and Julie Petruska.
6. References
APHA (American Public Health Association), American Water Works Association and
Water Environment Federation (1998). Standard Methods for the Examination of Water
and Wastewater, 20 th edition . American Public Health Association, ISBN 0-87553-235-
7, Washington, DC
Beltran, F.J.; Garcia-Araya, J.F. & Alvarez, P.M. (2001). pH sequential ozonation of domestic
and wine-distillery wastewaters. Water Research , Vol. 35, No. 4, pp. 929-936, ISSN:
0043-1354