Population equivalent (PE) or unit per capita loading, or equivalent person (EP), is a parameter for characterizing industrial wastewaters. It essentially compares the polluting potential of an industry (in terms of biodegradable organic matter) with a population (or certain number of people), which would produce the same polluting load. In other words, it is the number expressing the ratio of the sum of the pollution load produced during 24 hours by industrial facilities and services to the individual pollution load in household sewage produced by one person in the same time. This refers to the amount of oxygen-demanding substances in wastewater which will consume oxygen as it bio-degrades, usually as a result of bacterial activity.
Equation and base value
A value frequently used in the international literature for PE, which was based on a German publication, is 54 gram of BOD (Biochemical oxygen demand) per person (or per capita or per inhabitant) per day. This has been adopted by many countries for design purposes but other values are also in use. For example, a commonly used definition used in Europe is: 1 PE equates to 60 gram of BOD per person per day, and it also equals 200 liters of sewage per day. In the United States, a figure of 80 grams BOD per day is normally used.
If the base value is taken as 60 grams of BOD per person per day, then the equation to calculate PE from an industrial wastewater is:
![{\displaystyle PE={\dfrac {BOD\ load\ from\ industry\ \left[{\dfrac {kg}{day}}\right]}{0.060\ \left[{\dfrac {kg}{inhab\cdot day}}\right]}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/8799947964f43a0a66602509fba663484434b1b8)
Population equivalents for industrial wastewaters
BOD population equivalents of wastewater from some industries Type Activity Unit of production BOD PE [inhab/(unit/d)]
Food Canning (fruit/vegetables) 1 ton processed 500 Pea processing 1 ton processed 85-400 Tomato 1 ton processed 50-185 Carrot 1 ton processed 160-390 Potato 1 ton processed 215-545 Citrus fruit 1 ton processed 55 Chicken meat 1 ton processed 70-1600 Beef 1 ton processed 20-600 Fish 1 ton processed 300-2300 Sweets/candies 1 ton produced 40-150 Sugar cane 1 ton produced 50 Dairy (without cheese) 1000 L milk 20-100 Dairy (with cheese) 1000 L milk 100-800 Margarine 1 ton produced 500 Slaughter house 1 cow / 2.5 pigs 10-100 Yeast production 1 ton produced 21000 Confined animals breeding Pigs live t.d 35-100 Dairy cattle (milking room) live t.d 1-2 Cattle live t.d 65-150 Horses live t.d 65-150 Poultry live t.d 15-20 Sugar-alcohol Alcohol distillation 1 ton cane processed 4000 Drinks Brewery 1 m3 produced 150-350 Soft drinks 1 m3 produced 50-100 Wine 1 m3 produced 5 Textiles Cotton 1 ton produced 2800 Wool 1 ton produced 5600 Rayon 1 ton produced 550 Nylon 1 ton produced 800 Polyester 1 ton produced 3700 Wool washing 1 ton produced 2000-4500 Dyeing 1 ton produced 2000-3500 Textile bleaching 1 ton produced 250-350 Leather and tanneries Tanning 1 ton hide processed 1000-3500 Shoes 1000 pairs produced 300 Pulp and paper Pulp 1 ton produced 600 Paper 1 ton produced 100-300 Pulp and paper integrated 1 ton produced 1000-10000 Chemical industrial Paint 1 employee 20 Soap 1 ton produced 1000 Petroleum refinery 1 barrel (117 L) 1 PVC 1 ton produced 200 Steelworks Foundry 1 ton pig iron produced 12-30 Lamination 1 ton produced 8-50