Introduction

In essence, wastes are the products whose values have yet to be determined. However, this is a not widely shared view; throughout the developed world, food and agricultural wastewater is the scourge that needs to be kept out of sight and hopefully destroyed. Most wastewater management approaches are methods of concentration, conversion, and/or relocation of wastes, such as physicochemical and biological treatment, incineration, or land/sea disposal. This is in stark contrast to the early days of human development when agricultural and food wastewaters were fully utilized as fertilizers and animal feeds. Even today in some much less-developed nations, there are practices of utilizing food and agricultural wastewater for a variety of applications. It seems, as human beings get more affluent, the attitudes toward food wastewaters get more negative.

Management and treatment of agricultural and food wastewaters incur costs, and this is more than an annoying nuisance for food processors and other agribusiness sectors: As the environmental regulations and laws tighten, the costs will undoubtedly go up. This is certainly not good news for food and agriculture industries whose profit margins are thin and subject to volatile international agriculture commodity price swings. The best remedy for reducing the costs of treating and disposing food and agricultural wastewater is to reduce the amount of water used in the food and agricultural processing operations and to recycle spent water for reuse. Water consumption in the food industry is enormous, and any reduction of its use will ultimately ease the shortage in many parts of the world and environmental degradation. Still, certain use of water in food and agricultural processing is inevitable because the hygienic requirement is that any-

Table 8.1. Typical characteristics, estimated volume, and estimated organic loading of wastewater generated by the food processing industry in Georgia (Magbunua, 2000).

Estimated Estimated

Wastewater Organic

Volume, Typical Loading,

Industry Sector Mgal/yr Characteristics Tons/yr BOD

Meat and poultry products

10,730

1,800 mg/l BOD 1,600 mg/l TSS 1,600 mg/l FOG

80,600

Dairy products

500

2,300 g/l BOD 1,500 mg/l TSS 700 mg/l FOG

14,900

Canned, frozen, and pre-

2,080

500 mg/l BOD

4,300

served fruits and vegetables

100 mg/l TSS

Grain and grain mill products

130

700 mg/l BOD 1,000 mg/l TSS

300

Bakery products

530

2,000 mg/l BOD

4,400

Sugar and confectionery

140

500 mg/l BOD

300

products

Fats and oils

350

4,100 mg/l BOD 500 mg/l FOG

7,000

Beverages

3,660

8,500 mg/l BOD

91,000

Miscellaneous food

700

6,000 mg/l BOD

5,600

Preparations and kindred

3,000 mg/l TSS

BOD: biochemical oxygen demand; TSS: total suspended solids; FOG: fats, oils, greases; TKN: total Kjeldahl nitrogen.

thing that handles foods must be clean and safe. Table 8.1 provides a glimpse of the amount and characteristics of food and agricultural wastewater generated in the state of Georgia, U.S. Imagine what it is like for the food and agricultural wastewaters generated in the whole nation!

There is, however, a forward-looking way of viewing wastewater as commodity whose value in our society has yet to be determined. With this perspective, food and agricultural wastewater is nothing but the byproduct of food and agricultural processing and should be carefully explored for its possible value-added recovery and recycle.

The food industry as a whole is no stranger to this notion of recovering values from "wastes"—it has been a pioneer in using food wastes for animal foods and other nonfeed uses such as pectin recovery from apple pomace and edible oil from grape seeds (now nutraceuticals from the same "waste"). Many sources of food and agricultural wastewater contain substantial amounts of proteins, lipids, and polysaccharides, and flavoring compounds. Their recovery will undoubtedly reduce the organic loadings of wastewater treatment plants but also could offer financial returns that can be used to offset the cost of wastewater treatment and management. However, it must be emphasized that waste utilization in food and agricultural processing operations can be feasible only if the additional cost of processing and recovering products from wastewaters is lower than the alternative, i.e., an in situ wastewater treatment facility or paying service fees for discharging into a municipal sewage system. It is also important to remember that the utilization of solid wastes in food and agricultural wastewaters depends largely on whether the usable fraction of the wastes can be economically separated from the wastewater streams of processing plants.

There are just as many ways of recovering valuable materials as the food materials in the waste. Recovered food materials from wastewater pretreatment can be used as animal feed or used for fermentation to produce ethanol and even hydrogen gas that is microbially produced with glucose and sucrose in the absence of oxygen. Anaerobic digestion of scum, food debris, and primary and secondary sludges can produce biogas (methane as main useful component) as fuel. Table 8.2 is a tabulated list of the potential beneficial uses of food processing wastewaters in various sectors of the food processing industry.

Even sludges from wastewater treatment plants can be utilized beyond traditional agricultural applications; new applications of sludge products as heating fuels, ingredients for cement production, and other innovative products present a real prospect of zero-discharge bioresource utilization.

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