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Food Processing

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Food Processing

Dairy
The dairy industry includes plants that process milk to produce cheese, butter, bottled milk, ice cream, and dried milk or whey. Cleaning and sanitizing the processing equipment generates significant volumes of wastewater that must be highly treated prior to discharge. The major byproduct of the dairy industry is whey, which is usually processed further into salable products such as edible protein and lactose sugar.
Meat
The meat industry includes facilities that process cows, hogs, calves, ducks, turkeys, chickens, and fish. Products include fresh meats, smoked meats, canned meats and a wide variety of sausages. In addition there are small facilities that custom butcher and process domestic livestock and deer. The environmental issues are mainly the management of wastewater and the inedible animal parts.
Fruits and vegetables
The major commodities processed are snap beans, sweet corn, peas, potatoes, cabbage, cucumbers, cranberries, cherries and apples. Appropriate management of the inedible vegetable parts, such as sweet corn cobs and husks and potato peelings, are of environmental concern for this sector.
Wastewater Management
Food processing generates significant volumes of wastewater that is used for cleaning and sterilizing equipment, washing the products and for cooling. It is often not practical to recycle or reuse wastewater because of the need to meet strict sanitation standards demanded by consumers and required by regulations.
The pollutants in the wastewater are biodegradable organic material, (measured as biochemical oxygen demand (BOD)), nitrogen in several chemical forms, phosphorus and chloride. Prior to discharging wastewater to a lake or stream the wastewater must be treated in a biological treatment process to remove these pollutants or convert them to a non polluting chemical form. Many food plants discharge their wastewater to sanitary sewer to be treated in a publicly owned treatment works (POTW). Some food processing plants operate their own wastewater treatment systems. Plants that operate primarily in the summer months, such as vegetable processing, often discharge their wastewater to a land application system where the pollutants become nutrients for plants. 
The primary goal of effective wastewater management is to reduce the concentration of pollutants in the wastewater by improving the processing operations in order to limit the quantity of pollutants that are wasted.

Organic waste material

The biodegradable wastes measured by the BOD concentration in wastewater can be removed by conventional wastewater treatment systems that have an aeration and settling module. Nitrogen compounds can be removed or converted to a less harmful pollutant in the same treatment process. The cost of treatment is proportional to the quantity of BOD that must be removed. A food processing plant can be the most significant discharger of BOD to a wastewater treatment plant in smaller communities. Food processing equipment should be designed and operated so that high strength waste streams, such as whey or blood, are collected before mixing with the process wastewater. Best management practices include minimizing spills, completely emptying process and storage equipment prior to washing and sweeping waste from floors instead of washing down the floor drain.

Phosphorus

Phosphorus is a significant part of many food products and so any loss of product into the wastewater will increase the phosphorus concentration. Also, phosphorus is an ingredient in industrial strength cleaners. For example the dairy sector uses phosphoric acid as one step in cleaning pipelines, storage tanks and processing equipment. Best management practices include minimizing product loss to the sewer, choosing a substitute for high phosphorus cleaning chemicals and checking the composition of all processing materials to minimize the lose of those with high phosphorus.

Chlorides

Chloride ions in significant concentrations can be toxic to aquatic life. Chloride ions cannot be removed by any conventional wastewater treatment process. One significant source of chlorides is the waste of sodium chloride from salting the food product. Cheese is salted by spreading salt on the curds or dipping cheese blocks in salt brine tanks. Pollution prevention actions include precise application of salt to the curds, minimizing spills and drips when cheese blocks are lifted out of brine tanks and using brine as long as possible by filtering and sterilizing. High strength salt brine is used in processing cabbage into sauerkraut and cucumbers into pickles. Minimizing spills when moving product in and out of the processing tanks and reuse of brine by filtering and sterilization by heat are recommended practices.

In food processing plants and other businesses, significant chloride ions are discharged from the backwashing of water softeners with sodium chloride. Pollution prevention practices include arranging the piping so that only the water that must have the calcium and magnesium ions removed is passed through the water softener. The water softener should be regenerated only when all the ion sites are filled with magnesium or calcium instead of at set time intervals. Also the softener regeneration process can be optimized by adjusting the salt concentration and volume of regeneration water to precisely what is needed to refill all the ion sites with sodium.

Best Management Practices for Food Processing Byproducts

Solid waste and food by-products should always be managed to optimize opportunities for the best use in the following order:

  1. Use as Raw Material for Edible Products - The best possible use of a food by-product is as a material source for another food product. For example, the cheese-making sector has successfully developed a process and market for their whey by -product, which is 90% of the original volume of milk. An edible dried protein supplement is extracted by using innovative membrane technology. The remaining whey is a lactose sugar fraction which is used in baking, infant formula and pharmaceuticals.
  2. Use as Animal Food - Byproducts from the vegetable processing sector are frequently utilized to feed animals. After the corn kernels are removed from sweet corn, a large volume of cobs and husks remain. This waste can be fed directly to cattle or stored in a dense pile, so that oxygen is sealed out, and a fermentation process changes the material to silage for winter feed. Meat processors and renders use some of the inedible parts of butchered animals for pet food and mink food.
  3. Direct Landspreading for Nutrient Utilization - Most food processing wastes are rich in nitrogen, phosphorus, potassium and other plant nutrients and can be used as fertilizer. In many situations, food-processing wastes, with the exception of inedible animal parts, can be directly landspread without any additional processing. The DNR regulates the landspreading of industrial byproducts and a Wisconsin Pollutant Discharge Elimination System (WPDES) permit is required. The permit requires the waste generator to implement a management plan that limits the application rate to crop nutrient needs and obtain site approval.
  4. Composting to Produce a Soil Conditioner - Generally solid byproducts that can be landspread can also be composted. Composting will produce a more valuable soil conditioner that can be transported to a distant market if there are no crop fields near the generator. This will also eliminate the nuisance conditions, such as odor, that sometimes occur when wastes are stored waiting for proper field spreading conditions or when exposed on the land surface prior to incorporation into the soil. Composting also provides an opportunity to utilize other waste streams, such as non-salable grocery store produce, cafeteria food scraps or leaves to produce a compost for a specific market. Composing facilities are licensed by DNR's Bureau of Waste Management.
  5. Hauling to a Sanitary Landfill - Landfilling is the option of last resort and wastes should only be hauled to a landfill if all of the reuse alternatives have been considered and found to be unworkable. However, landfilling is a satisfactory way to dispose of waste because licensed sanitary landfills are designed to protect the environment by permanently burying the waste and capturing the leachate.
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Please note that this is the opinion of the author and is Not Certified by ICAR or any of its authorised agents.