Article Index
Water and Wastewater Use in the Food Processing Industry
Fruit and Dairy Processing
Meat and Poultry Processing
Grain Processing for Oils
All Pages


Fruit Processing (Canning, Freezing, Fermenting, etc.)
The initial preparation processes for canned, frozen, and fermented fruits are washing, sorting, trimming, peeling, pitting, cutting or slicing, inspecting, and grading. Unwanted and undesirable materials must be removed before the fruits undergo additional processing, but not all fruits are subject to each step. For example, cherries and plums may be canned whole and unpeeled whereas apples, peaches, and pears must be peeled and either cored or pitted before being canned. Peeling can be by hand or with machines, chemicals, or steam. After inspection and grading, the peeled fruits are conveyed mechanically or flumed to product handling equipment for processing.

Figure 35. Wastewater Loadings Per ton of Product from Canned Fruits
Fruit Flow (gallon/ton)
Apple 500,000
Apricot 500,000
Cherry 200,000
Citrus 300,000
Peach 400,000
Pear 400,000
Pineapple 50,000
Other Fruit 800,000

The converted fruit handling processes are can filling, syrup adding, exhausting and sealing, thermoprocessing, can cooling, and storing. Processing equip- ment and plant floor usually are cleaned at the end of each shift and so constitute a final source of waste materials.

Water and Wastewater Management
Several water conservation and waste prevention techniques are available by which to decrease water volume. These techniques include

  • The use of high-pressure sprays for clean-up.
  • The elimination of excessive overflow from washing and soaking tanks.
  • The substitution of mechanical conveyors for flumes, the use of automatic shut-off valves on water hoses.
  • The separation of can cooling water from composite wasteflow.
  • The recirculation of can cooling water. When can cooling water is not recirculated, it may be reused in caustic soda (NaOH) or in water peeling baths, in removal of NaOH after peeling, in primary wash of the raw material, in canning belt lubrication, and in plant cleanup operations1.

Dairy Processing
The processing of dairy products often entails various unit operations. These generally include the receiving and the storing of raw materials, the processing of raw materials into finished products, the packing and the storing of finished goods, and a number of ancillary processes (e.g., heat transferring and cleaning) associated indirectly with processing and distributing.

Equipment and facilities for receiving, transporting, and storing raw materials are much the same industrywide. Bulk carriers unload products in receiving areas by means of flexible lines or dump mate- rial into hoppers connected to fixed lines subsequently transferred by pump to storage. Storage facilities can be of the refrigerator, vertical, or silo type, with storage tanks containing either liquid or dry products and ranging in volume from a few thousand gallons to one million gallons or more.

Milk, a perishable product made up of fat, protein, carbohydrates, salts, and vitamins, is an ideal food for microorganisms as well as for humans. Thus, it needs to be protected from contamination, and much of the efforts of the dairy industry are directed to this end. Milk and its by-products are processed according to approved procedures, on machinery normally run no longer than about 20 hours per day. Much equipment is dismantled daily. Systems may be cleaned in place or after they are taken apart. Automated cleaning systems, now pre- dominant in the industry, require less labor but more water and cleaning chemicals than hand washing dismantled equipment does.

Wastewater and Management
Dairy processing wastewaters are gener- ated during the pasteurization and the homogenization of fluid milk and the production of dairy products such as butter, ice cream, and cheese. The principal constituents of these wastewaters are whole and processed milk, whey from cheese production, and cleaning compounds.
Water use in the dairy products industry depends on plant complexity and water-management practices. Process wasteloads also differ considerably and are influenced greatly by the extent to which the plant controls raw material and product losses. Raw wastewater loading for the American dairy industry is summarized by commodity segment in Figure 36.

Figure 36. Summary of American Dairy and Milk Processing Plant Effluent Loadings
Products Wastewater (kg ww/kg milk) range Wastewater (kg ww/kg milk) average
Milk 0.10-5.40 3.25
Cheese 1.63-5.70 3.14
Ice cream 0.80-5.60 2.80
Condensed milk 1.00-3.30 2.10
Butter   0.80
Powder 1.50-5.90 3.70
Cottage cheese 0.80-12.40 6.00
Cottage cheese and milk 0.05-7.20 1.84
Cottage cheese, ice cream, and milk 1.40-3.90 2.52
Mixed products 0.80-4.60 2.34

Milk product losses typically range from 0.5 percent in large, technologically advanced plants to greater than 2.5 percent in small, old plants. Given redoubled effort by management, water usage in most plants could be decreased to approximately 0.50 L/kg milk equivalent processed. Considerable improvements in water and waste management remain important and realistic industry goals.

In recent years, technological innovations with membrane systems have provided many new opportunities. For example, ultrafiltration now can be used instead of the biological separation of organic material from liquid substrate. And instead of using reverse-osmosis systems for tertiary waste treatment, some food plants use them to recycle internal liquid wastestreams. The outflow from reverse-osmosis treatment can be of better quality than the native water.