FISHERY BULLETIN: VOL, 74, NO. 4 



COD {Chemical oxygen demand): oxidation by 

 potassium dichromate. 



Residue: This term does not necessarily mean 

 solids, rather it is the results of or the substance 

 remaining from a separation process such as 

 filtering or drying. For example, if a solvent is 

 evaporated from oil, the resulting residue is a 

 liquid, not a solid. 



TR {Total residue): is the weight of material 

 remaining from a sample of the original screened 

 effluent after overnight drying at 103°C. 



FR {Filterable residue): is the residue of the 

 filtrate (GF/A glass filter) dried at 103°C. Drying 

 seafood effluents at 180°C (Environmental Pro- 

 tection Agency 1974) produced results that could 

 not be related to the TR and nonfilterable residue. 



NFR {Nonfilterable residue): is the residue 

 remaining on the glass filter after drying at 103°C. 

 Since the three residue terms are related and 

 provided drying conditions are the same, NFR can 

 be determined indirectly, i.e., TR - FR. 



5S {Settleable and floatable solids): This term has 

 caused considerable trouble to the industry and 

 researchers. By custom, the volume of the settled 

 portion in the Imhoff cone is measured and con- 

 sidered SS. However, this measurement does not 

 actually measure SS, because floatables are not 

 included in the reading. The term only has correct 

 meaning when SS is determined in milli- 

 grams/liter by difference: the NFR minus the 

 NFR of a sample taken from near the center of the 

 Imhoff cone after 1 h of settling. 



Sus. Sol. {Suspended solids): are the particulate 

 matter suspended in the center of the Imhoff cone, 

 i.e., the NFR of that area. 



TSS {Total suspended nonfilterable solids): This 

 term has also caused confusion. It means the dry 

 weight of all particulate matter (settleable, sus- 

 pended, floatable), i.e., the NFR. For both tech- 

 nical and grammatical reasons, NFR is the 

 preferred term. 



O&G {Oil and grease): content was determined 

 by a method in which the precipitated, filtered- 

 solids material plus Celite^ (used as a precipitation 

 aid) is extracted directly under anhydrous condi- 

 tions, using 2-propanol and petroleum ether 

 (Collins 1976). This technique extracts all lipidlike 

 material, including carotenoids. 



Protein: The nitrogen content was determined 

 by the macro-Kjeldahl method on 100- to 200-g 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



726 



samples and expressed as protein by multiplying 

 N by 6.25 (Horwitz 1965:273). 



Salt: Chloride was determined by the standard 

 AgNOs method and expressed as NaCl (Horwitz 

 1965:273). 



Subscripts: In this paper, we use subscripts to 

 identify the particular portion of the sample 

 tested. For example, CODtr is the COD of the 

 screened waste effluent, and COD^r is the COD of 

 the FR, i.e., the filtrate, not the actual dried FR. If 

 no subscript is used, we are referring to the test in 

 general or to the test on the original screened 

 sample, i.e., COD is the same as COD-tr. 



Industrially screened shrimp and crab effluents 

 were obtained from November 1973 through Feb- 

 ruary 1974 and from salmon effluents July 

 through September 1974. Since our purpose was to 

 compare data rather than characterize the level of 

 pollution in a plant, we took grab samples at 

 specific times during the production to get a useful 

 range of values. The following analyses were 

 made: COD^r, CODpR, TR, FR, NFR (i.e., TSS), SS, 

 protein, O&G, salt, and the COD of a sample from 

 the center of the Imhoff cone after 1 h of settling. 



In conducting these analyses we used the meth- 

 ods of the Environmental Protection Agency 

 (1974), unless otherwise indicated. The particulate 

 matter in our samples of fishery waste was so high 

 that the filter clogged frequently before the entire 

 sample had been filtered. For this reason, sample 

 sizes were reduced, where necessary, to 25 ml. 



The degree of pollutant in an effluent is affected 

 by the processes employed, species processed, and 

 the use of fresh or salt water in varying degrees 

 during processing. Mechanical shrimp peelers use 

 about 7 gallons of water per pound of shrimp. Salt 

 water from wells close to the shore or from the 

 ocean is sometimes used on the mechanical peelers. 

 The two main types of peelers vary in their 

 relative waste load. The Model A peeler peels raw 

 shrimp and generally has a higher waste load than 

 the Model PCA peeler that peels a steam-blanched 

 shrimp. 



RESULTS 



Study I— Shrimp: Analyses of effluents from a 

 shrimp plant processing with fresh water and 

 mechanical peelers (Model A). 



Over a 10-day period in December 1973, eight 

 samples of waste effluents were taken from the 

 underflow of the Bauer Hydrasieve (tangential 

 screen, 0.04-inch) and analyzed (Table 1). Aver- 

 ages for COD by analysis are as follows: 



