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Egg ProcessingEggs

Egg processing involves a series of unit operations whereby eggs are washed in hot water to remove contaminants such as feces, dirt, and feathers from the shells surface. In addition, eggs are further evaluated for defects (checks, blood spots, stains, etc.) and sorted according to weight. The acceptable eggs are then placed in cartons or flats according to grade and sold as shell eggs. Inferior eggs are packaged in flats and sent to a breaker for conversion into liquid eggs and food ingredients. Disposing of wastes from egg processing plants generally require permits from state and federal environmental agencies to ensure minimal environmental impact. These wastes include solids (broken eggs and shells) and liquids (e.g., wash water, cleaners, sanitizers, etc.). Solid waste are typically separated and sold (e.g., protein meal, calcium supplement) or disposed of (e.g., landfill) depending on economic markets. Solid waste or liquids that end up in the liquid waste stream are collectively referred to as wastewater. Table 1 shows a sample of wastewater characteristics for a discharge from a shell egg facility. Before being discharged this wastewater would need additional treatment to reduce regulated components (e.g., TSS, FOG, COD, TKN, Total Phosphorous) by 10 to 100 times.

Permits required for egg processing vary with the type of manufacturing (shell eggs, liquid eggs, egg (food) ingredients). The wastewater permit may be a municipal permit for those discharging into a publicly owned treatment works (e.g., city or municipality) or a National Pollution Discharge Elimination System (NPDES) permit if the facility treats its own wastewater and directly discharges into the environment. These permits specify maximum allowable limits for discharge parameters such as total flow, BOD5, COD, FOG, TKN, and Total Phosphorous. These limits are based many factors such as location, type of treatment available at POTW, type of discharge (river, municipality, land application, etc.).

TABLE 1: Compiled profile of wastewater from shell egg processing.

Parameter

Flow
Gal water/case (360 eggs)

pH
TSS
(mg/L)
FOG
(mg/L)
BOD5
(mg/L)
COD
(mg/L)
TKN
(mg/L)
Total
Phosphorus

(mg/L)
Range
2.8-3.5
10.0-12.0
400-4,150
n.r.
4,100– 13,500
5,000-27,000
30-200
6.0-52

TSS – Total Suspended Solids
FOG – Fat, Oil and Grease
BOD5 – A five day Biochemical Oxygen Demand
COD – Chemical Oxygen Demand
TKN – Total Kjeldahl Nitrogen
n.r. – not reported

Other Resources

Sustainability Resources for Eggs

 


FPEAC
Food Processing Environmental Assistance Center
Purdue University, Food Science Building, 745 Agriculture Mall Drive, West Lafayette, IN 47906
Phone: 765-494-7997 • FAX: 765-494-7953

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