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Water and Wastewater Use in the Food Processing Industry
Fruit and Dairy Processing
Meat and Poultry Processing
Grain Processing for Oils
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Grain Processing for Oils
The extracting, refining, and processing of edible oils produces a variety of waste products. This chapter, which focuses on conventional caustic refinements and on related downstream processes, briefly reviews major processes and facilities, especially as they relate to waste generation and control.

Process Components and Major Wastewater Sources
Figure 38 lists primary processes and associated wastewater loadings from a well-run fat and oil processing facility. Separate totals are presented with and without salad dressing and mayonnaise because these processes often are absent in a facility. Certain oil processing and refining operations have no oil seed processing facilities, but instead bring in crude vegetable oil. To account for this practice, adjustments can be made to the figures in the table. Data presented in Figure 38 are based on these operating parameters:
  1. Milling and extracting: 80,000 bushels per day.
  2. Caustic refining with single-stage water wash:60,000 lb/hr, nondegummed soybean oil.
  3. Semicontinual deodorizing with scrub cooler, barometric condenser with atmospheric cooling tower.
  4. Acidulating of soapstock and washwater with 90 to 95 percent recovery efficiency.
  5. Bottling line and/or other extensive liquid-oil packaging.
  6. Margarine, mayonnaise, and salad dressing production and packaging.
  7. Washing of tank cars for finished oil only (cars carrying crude oil excluded).
Figure 38. Fats and Oils Processes and Wastewater Loads from a Well-run Facility
Process Flow (gallons/daya, avg.)
Milling and extraction 75,000
Caustic refining 11,000
Further processing 5,000
Deodorizing 5,000
Acidulating 19,000
Tank car washing 5,000
Packaging 10,000
Subtotal 130,000
Margarine 70,000
Salad dressing/mayonnaise 50,000
Total 250,000
agallons/day = gallons per day

Obviously, operations of an atypical size or those omitting certain processes will have different waste loads. This applies especially to operations involved in acidulation or in mayonnaise and salad dressing processing. The effects of process control and its impacts on wastewater loading are outlined in the next section. As noted, these loadings are representative for an operation running reasonably well from a process loss control standpoint. But actual loadings depend on how well plants are run.

A final source of wastewater is contaminated runoff from truck and rail loadout areas and from tank farm drainage. During rainy periods, runoff from these sources can contribute the equivalent of five to 10 gal/min to total daily average flow and, in fact, may affect peak flows to a much greater extent.