Population equivalent is defined as:
1
ratio of total standard BOD5 of industrial sewage per day to standard BOD5 of domestic sewage per person per day
2
ratio of standard BOD5 of domestic sewage per person per day to total standard BOD5 of industrial sewage per day
3
sum of standard BOD5 of domestic sewage per person per day and total standard BOD5 of industrial sewage per day.
4
difference between total standard BOD5 of industrial sewage per day and standard BOD5 of domestic sewage per person per day