Fruit and Vegetable Processing
The fruit and vegetable processing indus- tries may be described as consisting of two segments: fresh pack and processing. The former collects crops and field packs them into lug boxes or bulk bins for shipment to a produce finishing plant. Crops are cooled to preserve integrity and fumigated or treated to control insect infesta- tion or microbial disease development. The processing segment, or packers, includes all unit operations, extending the shelf life of food being processed and adding value through produce modification to satisfy market niches.

The fresh pack segment of the industry shares unit operations with the processing segment. These operations are the sorting/trimming, washing, grading, and packing lines. But after the packing lines, additional unit operations may add to the waste generating scheme for the processing segment alone. Additional operations may include combinations of peeling, stemming, snipping, pitting, trimming, chopping, and blanching. In some instances, the final product is dehydrated (e.g., chopped onions). In others, it is packaged and processed. Processing can include one treatment or a combination of several treatments (e.g., acidifying, brining, freezing, or cooking).

Major water use and waste generation points associated with the fruit and vegetable industry include the washing steps for raw and processed produce, peeling and pitting practices, blanching, fluming the produce after blanching, sorting, and conveying the product within the plant. Reducing size, coring, slicing, dicing, pureeing, and juicing process steps, as well as filling and sanitizing activities after processing, also contribute to the wastestream.

Wastewater Characterization
Major wastewater characteristics to be considered for the vegetable and fruit processing industry are the wide ranges of wastewater volume and the concentrations of organic materials. Wastewater characteristics can be influenced by a number of factors such as the commodity processed, the process unit operations used, the daily-production performance level, and the seasonal variation, e.g., growing condition and crop age at harvest. Figure 34 presents historical data collected from raw wastewater discharged from the vegetable and fruit processing industry.

Water Use and Wastewater Sources
In the processing environment for vegetable and fruit material handling, heating, cooling, and packaging, there are six major contributing point sources for waste. These sources are the following operations: (1) raw produce washing, grading, and trimming, (2) washing after steam/lye peeling and/or size reducing, (3) blanching and fluming, (4) filling, (5) sanitation/plant cleanup, and (6) pro- cessed product cooling. Plant manage- ment practices greatly influence process operation efficiency relative to final product yield and waste quantity gener- ated. (Refer to Figure 34 for industrial variability.)

Water use by the vegetable and fruit processing industry is essential to the washing, heating, and cooling of food products. But the industry has adopted a number of practices, showing heightened sensitivity to the need for water conservation:

1. Use of air flotation units to remove suspended debris from raw crop materials
2. Recovery and reuse of process water throughout the processing plant.
3. Decrease of water volume use in peeling and pitting operations, as well as decrease of raw product losses.
4. Separation of waste process streams at their sources, for potential by-product use.
5. Countercurrent reuse of wash and flume/cooling waters.
6. Separation of low and high strength wastestreams.
7. Installation of low-volume, high- pressure cleanup systems.
8. Conversion from water to steam blanching.
9. Use of air cooling after blanching.

* Excerpts from "Waste Management and Utilization In Food Production and Process," CAST, October 1995.

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.

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.

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.

Innovations
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.

Meat and Poultry Processing
The meat and poultry processing industries in the United States together make up a $75.6 billion per year industry. The U.S. Department of Commerce reported that the value of red meat shipments for 1988 totaled $46.8 billion. Most red meat processing plants are located in the Midwest; most poultry processing plants are in the Southeast and the Mid-Atlantic. Processing of prepared meats, including canned cooked products, luncheon meats, hot dogs, bacons, stews, and other ready-to-eat meat products, has expanded rapidly in recent years.

Waste and By-Products
Most waste products are recovered somehow by the industry. Blood, feathers, and bone usually are processed into a meal product for animal feed. Similarly, meat scraps unsuitable for processing into food products are sold or given to rendering facilities for processing into animal and pet foods. The ultimate characteristics of solid materials and wastewaters generated by these source areas in a plant and unrecovered for another use differ greatly and are affected by:

1. animal size and type
2. processing level
3. conveyance means
4. processing water use
5. cleanup and housekeeping procedures

Water Usage
Water use for broiler processing typically ranges from 3.5 to 10.0 gal./bird; for turkeys, 11 to 23 gal./bird. Flow rates of 350 gal./animal have been reported for beef slaughtering plants. In one beef slaughtering operation, water use dropped from 458 to 187 gal/head after water conservation measures were adopted. Similar water use numbers appear in the examples in Figure 37.

Water is used for chilling, scalding, can retorting, washing, cleaning, and waste conveying. For example, poultry processing uses approximately 3.5 to 7.0 gallons of water per bird of four-pound average weight. All broiler processing plants are required to have a scalder overflow rate of 0.25 gal./bird and a chiller overflow rate of 0.50 gal./bird. In many instances, this water is used in the plant for the transport of feathers and offal from the processing area. One researcher, studying a broiler processing plant, reported that processing accounted for 76 percent of the water use, with 13 percent used in cleanup and 12 percent used in downtime.

Beef processing water usage, primarily from carcass washing and process cleanup, has been reported in the range of 150 to 450 gallons per animal processed. As a general rule, meat processors use about one gallon of water per pound of processed hamburger meat.

Use and Minimization of Wastes
The amount of wastewater generated by the industries can be decreased largely through changes in cleanup practices. Water use can be minimized by means of commercially available high-pressure, restricted flow hoses, which can be fit with automatic shutoffs to prevent water loss during inactivity. Many materials can be handled mechanically. For example, flour and other dry material can be vacuumed from the floor and augers and conveyors can be used to transport scrap meat and viscera.

Chiller and scalder water is reused in most poultry processing plants for flushing water to remove offal and feathers. Reconditioning of chiller overflow through the use of filtration and ultraviolet irradiation has been recommended. Limits to use include the potential of bacterial contamination by coliforms or by Escherichia coli. Recycling is limited by the characteristics of the wastestream and by the potential for contamination of food products.

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.

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.