62    TREATMENT OF SEAFOOD PROCESSING WASTEWATER
BY DISSOLVED AIR FLOTATION CARBON
ADSORPTION AND FREE CHLORINATION
Milos Krofta, President
Krofta Engineering Corporation
Lenox, Massachusetts 01240
Lawrence K. Wang, Director & Professor
Lenox Institute for Research
Lenox, Massachusetts 01240
Curtis D. Pullman, Principal Scientist
KBN Engineering & Applied Science Inc.
Gainsville, Florida 32602
INTRODUCTION
A system consisting of a microstrainer, a dissolved air flotation (DAF) clarifier and a granular
activated carbon (GAC) column was proven to be feasible for treatment of the 200-gpm Homer Smith
scallop processing wastewater containing 3184 mg/L COD, 1905 mg/L TSS, 122 ppb cadmium, 387
ppb zinc and 27.7 mg/L ammonia nitrogen. DAF alone removed 83.5% COD, 97.4% TSS, 19%
ammonia nitrogen, 56.6% cadmium, and 67.4% zinc when 70 mg/L alum and 70 mg/L activated
sodium aluminate (both as A1203), and 6 mg/L polymer 2PD-462 were dosed to DAF. DAF chemical
cost is estimated to be $0.8146/1000 gal. Bioassay testing indicates that the DAF effluent was not
toxic to fish. With an additional 10 mg/L sodium carbonate and 10 mg/L H3P04 at pH 6.9, removals
of cadmium and zinc by DAF were increased to 82% and 92.5%, respectively. Combined DAF-GAC
treatment gave 97.5% COD removal and 94.6% ammonia nitrogen removal. Free chlorination
removed 100% bacteria and ammonia nitrogen.
RESEARCH APPROACH AND OBJECTIVES
The authors conducted preliminary studies at the existing scallop processing facility of Homer
Smith Seafood Company (HSSC) in Green Cove Springs, Florida, toward developing a feasible
permanent wastewater treatment plant for HSSC which currently has only a microstraining unit and a
small holding tank for grit removal.
Relative to major improvements at the existing HSSC waste treatment facility, the author's joint
preliminary evaluations indicate that dissolved air flotation may be a feasible method for clarification
of the HSSC scallop processing wastewater prior to discharge into a near-by creek eventually flowing
to St. Johns River, near Jacksonville, Florida.
In March 1985, the Lenox Institute for Research (LIR) was retained by HSSC through Environmental Science and Engineering Inc. (ESE), Gainsville, Florida, to participate in a professional engineering study for treatment of the HSSC wastewater by dissolved air flotation and any other necessary
supplemental processes. The LIR Chemical and Microbiological Laboratory is approved by the
Commonwealth of Massachusetts and the U.S. Environmental Protection Agency for water quality
testing.
More specifically, the primary objective of the LIR laboratory and pilot plant testings was to
determine the efficiency of dissolved air flotation (DAF) and necessary supplemental processes for
wastewater treatment in order to meet the following tentative target effluent standards:
pH = 6.5 -8.5 units
TSS = 100 mg/L or less
Total Coliform = 1 coliform/100 iriL
COD Removal = over 90%
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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