to design a TW we can start from the population count. With the number of habitant equivalent we can have the water volume and an extimation of the pollution of the wastewater.
The problem rise we we don't have a single room with 4, 6.. 10 person that live inside...but when we work for cinemas... restaurant..... hotel..... and other places with a lot of persons that can produce water volume?
Don't worry, it is simple.
We can transform the total population number in habitant equivalent and organic loading. Here the way:
1) do you have a bar of 50 mq? Your theoretical production is 7,5 cubic meter a day.
2) do you have an office with 10 employees? your production is 0,65 cubic meter a day
3) do you have a cinema with 1500 seats? your production is 15 cubic meter a day.
It is simple but for each example you have to do few considerations:
1) do you have the possibility to measure the water consumption? If yes compare this with the 7,5 cubic meter you have obtained and make the right consideration. Do you organize party with more seats that ususally are on your bar? consider it!.. an so on...
2) do you have shower in this office? consider 90-110 L per uses...
3) your cinema is open only on sunday? or all week long? you have to consider this in order to design the pipe line and the tanks... etc
Something more on: