Section 9. FOOD WASTES
ULTRAFILTRATION TREATMENT OF SEAFOOD
PROCESSING WASTEWATERS
Allen C. Chao, Assistant Professor
Department of Civil Engineering
Jeffy L. Machemehl, Associate Professor
Department of Marine Science & Engineering
Efren Galarranga. Graduate Student
Department of Civil Engineering
North Carolina State University
Raleigh, North Carolina 27650
BACKGROUND
This paper presents the preliminary results of a research funded by the Sea Grant College
Program, University of North Carolina on the use of an ultrafdtration technique as an
alternative method for treating seafood processing wastewaters. The research was initiated
in response to the needs of seafood industries for providing a suitable treatment of their
processing wastewaters.
Harvesting and processing seafood is an important source of income for residents of
the nation's coastal states. Over five bUlion pounds of seafood were landed annually in the
United States, and two million pounds were landed in North Carolina in 1977 [1, 2]
Water is needed for processing the harvest into marketable products. The annual water
consumption by the seafood processing industries is estimated to be 2.5 billion gallons
[3]. Most of the consumed water is discharged as seafood processing wastewaters.
In 1972 the U.S. Environmental Protection Agency (EPA) established the National
Effluent Limitations for all point discharges. The seafood industries must now treat their
wastewaters to meet discharge limitations. The best available control technology (BAT)
must be employed by the industries in order to meet the standards to be enforced in 1983
[4]. These standards are often referred to as the BAT standards or the 1983 standards.
The BAT standards are considered by most industries as being unreasonable because
they cannot be achieved economically. In 1978, the EPA reviewed the BAT standards
in light of section 304-D-4 of the clean water act and established the "best conventional
pollutant control technology" (BCT) to replace the BAT or the 1983 standards. The BCT
standards are less stringent. For seafood industries, however, the BAT standards are to be
enforced in the future. This has resulted because EPA was able to prove that the BAT
standards are reasonable for 14 of the 27 seafood industry subcategories [5]. Later in
1979, EPA further justified the reasonableness of ten additional seafood subcategories
[6]. Therefore, the 1983 standards wdl have to be achieved by the industries if current
requirements prevad.
The seafood industries seem to have inadequate treatment facUities for the treatment
of their processing wastewaters to meet the proposed effluent standards. Current treatment
practices are limited to dissolved air flotation and screening with fine mesh [7-11]. These
techniques can only remove coarse (and some colloidal) particles [12]. The treated
effluents may exceed the current limitations imposed by present guidelines (the 1977
standards). They wUl not meet the 1983 standards [12, 13].
The BAT technology recommended by EPA often refers to secondary biological systems.
Extended aeration and lagoons are generally mentioned as examples for treating seafood
wastewaters [4]. In the biological processes, the organic matter is converted into settleable
biological mass which is then separated from the liquid. The separated sludge must be
further dewatered prior to disposal.
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